UNIVERSITY OF WISCONSIN SYSTEM SOLID WASTE RESEARCH PROGRAM. Leaching of Trace Elements from Gray Iron Foundry Slags

Transcription

1 UNIVERSITY OF WISCONSIN SYSTEM SOLID WASTE RESEARCH PROGRAM Leaching of Trace Elements from Gray Iron Foundry Slags 2008 Mitchel A. Eberhardt and Dr. Craig H. Benson Department of Civil and Environmental Engineering University of Wisconsin-Madison

2 EXECUTIVE SUMMARY i Gray iron slags are byproducts of iron castings, which are composed of impurities skimmed off during melting of iron ore and/or scrap iron at foundries. For the last three decades, most slag has been disposed in landfills. However, beneficial uses of slag in infrastructure construction are of interest. A concern, however, is that slag may release hazardous trace elements, causing pollution of soil and groundwater. This report describes a leaching study conducted on five foundry slags from gray iron foundries located in Wisconsin. A natural sand from Wisconsin was also tested for comparison purposes. Batch water leach tests (WLTs) and column leach tests (CLTs) were conducted on each of the foundry slags. WLTs were conducted as a rapid and inexpensive assessment of leaching potential, whereas the CLTs were conducted to more closely simulate flow-through conditions that occur in the ground. CLTs were performed under continuous saturated flow at fast and slow flow rates, periodic flow with air circulation, and periodic flow with carbon dioxide (CO 2 ) circulation. The effects of washing the slag prior to testing were also investigated. Leachate from the slags were analyzed for 16 trace elements (Ag, Al, As, Ba, Be, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, Tl, and Zn). Trace element concentrations in leachate from the CLTs followed four different patterns: first flush (decreasing concentration over time), delayed (increasing concentration over time), steady-state (relatively constant concentrations with time), and no detection (all samples did not have concentrations above the detection limits). Introduction of air or CO 2 resulted in a cycling pattern for some of the trace elements. The cycling pattern consisted of one of the four primary release patterns being repeated during subsequent periods of continuous water flow. Peak concentrations from the continuous-flow CLTs were found to be on average 30 times greater than the WLT concentrations. Peak concentrations from one or more slags

3 ii were found to exceed Wisconsin NR 140 groundwater enforcement standards for 6 trace elements, 12 trace elements exceeded Wisconsin NR 538 Category 1 byproduct applications, and 4 trace elements exceeded Wisconsin NR 538 Category 2 & 3 byproduct applications. Repeatability analysis conducted on the continuous-flow CLTs showed that peak concentrations from the CLTs varied on average by a ratio of 3.6:1, and all but one of the peak concentrations were within one order of magnitude from the average peak concentration. Peak concentrations were on average lower for the slow CLTs, although 14% of the trace elements did exhibit higher peak concentrations at the slow flow rate. Introduction of air in the CLTs typically decreased peak concentrations. The air may have oxidized the surface of the slag particles, potentially increasing solubility of some trace elements while reducing solubility of other trace elements. Introduction of CO 2 in the CLTs typically increased peak concentrations by a ratio of 6:1, on average. The introduction of CO 2 also reduced the ph by 2 to 3 standard units, which likely caused increased leaching of trace elements, as most trace elements are more soluble at a lower ph. Washing was shown to reduce peak concentrations for slags with peak concentrations above 20 µg/l for the continuous-flow CLTs, but had no discernable effect on peak concentrations below 20 µg/l. For trace elements where washing reduced peak concentration, the peak concentration was typically reduced by a factor of 2.

4 ACKNOWLEDGEMENTS iii Financial support for this study was provided by the State of Wisconsin s Solid Waste Research Program (SWRP), which is administered by the University of Wisconsin System. The findings and opinions of this report are solely those of the authors. Endorsement by SWRP is not implied and shall not be assumed.

5 TABLE OF CONTENTS iv EXECUTIVE SUMMARY... i ACKNOWLEDGEMENTS...iii LIST OF TABLES... vi LIST OF FIGURES... x 1. INTRODUCTION BACKGROUND Foundry Slag Previous Leaching Studies on Slags MATERIALS Control Material Gray Iron Foundry Slags METHODS WATER LEACH TESTS COLUMN LEACH TESTS Continuous Flow Tests Periodic Flow with Air Circulation Tests Periodic Flow with Carbon Dioxide Circulation Tests CHEMICAL ANALYSIS WATER LEACH TEST AND TOTAL ELEMENTAL ANALYSIS RESULTS CLT RESULTS RELEASE PATTERNS AQUEOUS CHEMISTRY INDICATORS CONTINUOUS-FLOW CLT CONCENTRATIONS vs. NR 140 ESs CONTINUOUS-FLOW CLT CONCENTRATIONS vs. NR 538 CRITERIA COMPARISON OF CLT CONCENTRATIONS TO WLT CONCENTRATIONS REPEATABILITY OF THE CONTINUOUS-FLOW CLTs CONTINUOUS FLOW WITH SLOW FLOW RATE CLTs Release Patterns Aqueous Chemistry Indicators Peak Concentrations Cumulative Concentrations Comparison to Regulatory Standards...41

6 v 6.8 PERIODIC FLOW WITH AIR CIRCULATION CLTs Release Patterns Aqueous Chemistry Indicators Peak Concentrations Cumulative Concentrations Comparison to Regulatory Standards PERIODIC FLOW WITH CARBON DIOXIDE CIRCULATION CLTs Release Patterns Aqueous Chemistry Indicators Peak Concentrations Cumulative Concentrations Comparison to Regulatory Standards WASHED SLAG CLTs WITH CONTINUOUS FLOW Release Patterns Aqueous Chemistry Indicators Peak Concentrations Cumulative Concentrations Comparison to Regulatory Standards SUMMARY AND CONCLUSIONS REFERENCES...71

7 LIST OF TABLES vi Table 3.1. Material properties of the 5 slags and the natural sand Table 3.2. Chapter NR 538 TEA criteria and results. Concentrations exceeding Category 1 are in BOLD and concentrations exceeding Category 2 are indicated with an asterisk (*) Table 3.3. Major chemical components of the 5 slags in this study Table 4.1. Table 5.1. Summaries of detection limits (DL) and limits of quantitation (LOQ) for WLTs and CLTs Concentrations of trace elements in WLT leachates compared to NR 140 ESs. Concentrations exceeding NR 140 ESs are shown in BOLD Table 5.2. Beneficial reuse categories and reuse applications from NR Table 5.3. Table 6.1. Table 6.1. Concentrations of trace elements in WLT leachates compared to NR 538 Category 1. Concentrations exceeding NR 538 Category 1 are shown in BOLD Summary of release patterns for the CLTs (Ag to Cu). Release patterns in BOLD indicate a significant change from the release pattern for the continuous-flow CLTs Summary of release patterns for the CLTs (Fe to Zn). Release patterns in BOLD indicate a significant change from the release pattern for the continuous-flow CLTs Table 6.2. Release patterns from the continuous-flow CLTs Table 6.3. Table 6.4. Table 6.5. Summary of minimum (min), maximum (max), and steady-state (SS) aqueous chemistry indicators (ph, EC, Eh) for the CLTs Peak CLT concentrations (µg/l) from the continuous-flow CLTs. Concentrations exceeding Enforcement Standards concentration criteria are shown in BOLD Cumulative concentrations (µg/l) from the continuous-flow CLTs. Concentrations exceeding NR 140 concentration criteria are shown in BOLD

8 Table 6.6. Table 6.7. vii Peak CLT concentrations (µg/l) from the continuous-flow tests compared to WLT concentration criteria from NR 538. Concentrations exceeding Category 1 WLT concentration criteria are in BOLD and concentrations exceeding Category 2 & 3 WLT concentration criteria are indicated with an asterisk (*) Cumulative concentrations (µg/l) from the continuous-flow CLTs compared to NR 538 WLT concentration criteria. Concentrations exceeding NR 538 Category 1 WLT concentration criteria are shown in BOLD and concentrations exceeding Category 2 & 3 WLT concentration criteria are indicated with an asterisk (*) Table 6.8. Release patterns for the slow CLTs Table 6.9. Summary of peak concentrations (µg/l) for the CLTs (Ag to Cu) Table 6.9. Summary of peak concentrations (µg/l) for the CLTs (Fe to Zn) Table Summary of cumulative concentrations (µg/l) for the CLTs (Ag to Cu) Table Summary of cumulative concentrations (µg/l) for the CLTs (Fe to Zn) Table Peak concentrations from the slow CLTs compared to peak concentrations from the continuous-flow CLTs. The higher concentration between the two tests is labeled with slow for the slow CLTs, fast for the continuous-flow CLTs, and same for concentrations that are approximately equal or concentrations from both tests are below the LOQ Table Peak Concentrations (µg/l) from the slow CLTs compared to NR 140 ESs and NR 538 Criteria. Concentrations above NR 140 ESs are shown in BOLD. Concentrations exceeding Category 1 are shown in BOLD and concentrations exceeding Category 2 & 3 are indicated with an asterisk (*) Table Table Cumulative concentration (µg/l) from the slow CLTs compared to NR 538. Concentrations exceeding Category 1 are shown in BOLD and concentrations exceeding Category 2 & 3 are indicated with an asterisk (*) Cumulative concentrations (µg/l) from the slow CLTs compared to NR 140 ESs. Concentrations exceeding the ESs are shown in BOLD Table Release patterns observed for the air CLTs... 98

9 Table viii CLT yielding higher peak concentration for continuous-flow and air CLTs; air indicates the air CLT had a higher concentration, fast indicates that continuous-flow CLT had higher a concentration, and, same indicates that concentrations are approximately equal or concentrations from both CLTs are below the LOQ Table Peak concentrations (µg/l) from the air CLTs compared to NR 140 ESs and NR 538 Criteria. Concentrations above NR 140 ESs are shown in BOLD. Concentrations above NR 538 Category 1 are shown in BOLD and concentrations above Category 2 & 3 are indicated with an asterisk (*) Table Table Cumulative concentration (µg/l) from the air CLTs compared to concentrations from NR 538. Concentrations exceeding Category 1 are shown in BOLD and concentrations exceeding Category 2 & 3 are indicated with an asterisk (*) Cumulative concentrations (µg/l) from the air CLTs compared to NR 140 ESs. Concentrations exceeding the ESs are shown in BOLD Table Release patterns for the CO 2 CLTs Table Table Peak concentrations from the CO 2 CLTs compared to peak concentrations from the continuous flow CLTs. The higher concentration between the two tests is labeled with CO 2 for the CO 2 CLTs, fast for the continuous flow CLTs, and same for concentrations that are approximately equal or concentrations from both tests are below the LOQ Cumulative concentrations (µg/l) from the CO 2 CLTs compared to NR 538. Concentrations exceeding Category 1 are shown in BOLD, concentrations exceeding Category 2 & 3 are indicated with an asterisk (*), and concentrations exceeding Category 4 are shown with two asterisks (**) Table Peak Concentrations (µg/l) from the CO 2 CLTs compared to NR 140 ESs and NR 538 Criteria. Concentrations above NR 140 ESs are shown in BOLD. Concentrations exceeding Category 1 are shown in BOLD, concentrations exceeding Category 2 & 3 are indicated with an asterisk (*), and concentrations exceeding Category 4 are shown with two asterisks (**) Table Cumulative concentrations (µg/l) from the CO 2 CLTs compared to NR 140 ESs. Concentrations exceeding the ESs are shown in BOLD Table Release patterns for the washed CLTs

10 Table Table Table Table ix CLT yielding higher peak concentration for continuous-flow and washed CLTs; washed indicates the washed CLT had a higher concentration, fast indicates that continuous-flow CLT had higher a concentration, and, same indicates that concentrations are approximately equal or concentrations from both CLTs are below the LOQ Peak concentrations (µg/l) from the washed CLTs compared to NR 140 ESs and NR 538 Criteria. Concentrations above NR 140 ESs are shown in BOLD. Concentrations above NR 538 Category 1 are shown in BOLD and concentrations above Category 2 & 3 are indicated with an asterisk (*) Cumulative concentration (µg/l) from the washed CLTs compared to concentrations from NR 538. Concentrations exceeding Category 1 are shown in BOLD and concentrations exceeding Category 2 & 3 are indicated with an asterisk (*) Cumulative concentrations (µg/l) from the washed CLTs compared to NR 140 ESs. Concentrations exceeding the ESs are shown in BOLD

11 LIST OF FIGURES x Figure 3.1. Particle size distribution curves for the 5 slags and sand Figure 4.1. Schematic of column leach test setup Figure 4.2. Photograph of columns, flow pump, and influent container Figure 4.3. Photograph of top of column, showing effluent end of column with sample collection bag Figure 4.4. Schematic of humidifier used for periodic flow with air or CO 2 tests Figure 6.1. Examples of FF (ARC f-3, Mn), D (ARC f-3, Al), linearly D (ARC f-1, Al), and SS (MAN a-4, Se) release patterns Figure 6.2. Common ph release patterns observed in the continuous-flow CLTs Figure 6.3. Common EC release patterns observed in the continuous-flow CLTs Figure 6.4. Common Eh release patterns observed in the continuous-flow CLTs Figure 6.5. Figure 6.6. Figure 6.7. Figure 6.8. Peak CLT concentrations from the continuous-flow CLTs vs. WLT concentrations. The geometric mean of the CLT concentrations divided by the WLT concentrations is 29.8:1. A total of 30 of 80 trace elements were below the detection limit for either the CLTs or the WLTs and are not shown. Another 20 of the 80 total trace elements are not shown because of failure of the ICP calibration Cumulative CLT concentrations from the continuous-flow CLTs vs. WLT concentrations. The geometric mean of the CLT concentrations divided by the WLT concentrations is 4.3:1. A total of 27 of 80 trace elements were below the detection limit for the WLTs and are not shown. Another 20 of the 80 total trace elements are not shown because of failure of the ICP calibration Cumulative CLT concentrations for the continuous-flow CLTs adjusted to a LS ratio of 20:1 vs. WLT concentrations. The geometric mean of the CLT concentrations divided by the WLT concentrations is 0.66:1. A total of 27 of 80 trace elements were below the detection limit for the WLTs and are not shown. Another 20 of the 80 total trace elements are not shown because of failure of the ICP calibration Histogram of ratios of maximum concentration to the average concentration and minimum concentration to the average concentration without DLs

12 Figure 6.9. Figure Figure Figure xi Ratios of the log (maximum concentration over the average concentration) and log (minimum concentration over the average concentration). The DL cutoff line is the approximate concentration of the DLs Histogram of ratios of maximum concentration to the average concentration and minimum concentration to the average concentration with DLs applied Histogram of ratios of maximum concentration to the average concentration and minimum concentration to the average concentration for the second and third repetitions of the repeatability CLTs Histogram of ratios of maximum concentration to the average concentration and minimum concentration to the average concentration of the cumulative concentrations for the repeatability CLTs Figure Common ph release patterns observed in the slow CLTs Figure Common EC release patterns observed in the slow CLTs Figure Common Eh release patterns observed in the slow CLTs Figure Figure Figure Peak concentration from slow CLTs vs. peak concentration from continuous-flow CLTs. The geometric mean of the slow CLT concentrations divided by the continuous-flow CLT concentrations is 0.46:1. A total of 32 of 64 trace elements were below the detection limit for either of the CLTs and are not shown. Another 8 of the 64 total trace elements are not shown because of failure of the ICP calibration Cumulative concentration from slow CLTs vs. cumulative concentration from the continuous-flow CLTs. Points above the 1:1 line indicate that the cumulative concentration is higher for the slow CLT than the continuous-flow CLT. A total of 6 of 64 trace elements were below the detection limit for the continuous-flow CLTs and are not shown. A total of 8 of 64 trace elements are not shown because of failure of the ICP calibration Release pattern of Se for ARC slag changing from FF (continuousflow) to D (air) (a), and the release pattern of Se for SHN slag changing from FF (continuous-flow) to SS (air) (b)

13 Figure xii Example of a FF cycling release pattern within a D release. Each of the eight vertical lines represents air flow in the column. If cycling is ignored the overall release pattern observed is classified as D. Each cycle (not including the initial samples before air was first introduced) is classified as FF, since the concentration is high initially and decreases over the course of the liquid-flow period Figure Common ph release patterns observed in the air CLTs Figure Common EC release patterns observed in the air CLTs Figure Common Eh release patterns observed in the air CLTs Figure Figure Figure Figure Figure Peak concentration from air CLTs vs. peak concentration from continuous-flow CLTs. The geometric mean of the slow CLT concentrations divided by the continuous-flow CLT concentrations is 0.88:1. A total of 27 of 64 trace elements were below the detection limit for either of the CLTs and are not shown. Another 8 of the 64 total trace elements are not shown because of failure of the ICP calibration Cumulative concentration from air CLTs vs. cumulative concentration from continuous-flow CLTs. Points above the 1:1 line indicate that the cumulative concentration is higher for the air CLT than the continuous-flow CLT. A total of 6 of 64 trace elements were below the detection limit for the continuous-flow CLTs and are not shown. A total of 8 of 64 trace elements are not shown because of failure of the ICP calibration Disappearance of Al from the SHN slag leachate with the introduction of CO 2 (solid squares) compared to the continuous-flow CLT (open circles) release pattern Release pattern for Fe from the ARC slag from the CO 2 CLTs showing the large range in concentration observed over one cycle. Vertical lines correspond to periods of CO 2 flow Examples of cycling observed in (a) ph and (b) Eh from the ARC slag for the CO 2 CLTs. Vertical lines correspond to periods of CO 2 flow Figure Common ph release patterns observed in the CO 2 CLTs Figure Common EC release patterns observed in the CO 2 CLTs Figure Common Eh release patterns observed in the CO 2 CLTs

14 Figure Figure Figure xiii Peak concentration from CO 2 CLTs vs. peak concentration from continuous-flow CLTs. The geometric mean of the CO 2 CLT concentrations divided by the continuous-flow CLT concentrations is 6.0:1. A total of 24 of 64 trace elements were below the detection limit for either of the CLTs and are not shown. Another 8 of the 64 total trace elements are not shown because of failure of the ICP calibration Cumulative concentration (µg/l) from CO 2 CLTs vs. cumulative concentration (µg/l) from the continuous-flow CLTs. Points above the 1:1 line indicate that the cumulative concentration is higher for the CO 2 CLT than the continuous-flow CLT. A total of 6 of 64 trace elements were below the detection limit for the continuous-flow CLTs and are not shown. A total of 8 of 64 trace elements are not shown because of failure of the ICP calibration Conceptual combined leaching (Total) of small, high surface area particles (Small) and large particle (Large) Figure Common ph release patterns observed in the washed CLTs Figure Common EC release patterns observed in the washed CLTs Figure Common Eh release patterns observed in the washed CLTs Figure Figure Peak concentration from washed CLTs vs. peak concentration from continuous-flow CLTs. The geometric mean of the washed CLT concentrations divided by the continuous-flow CLT concentrations is 0.48:1. A total of 29 of 64 trace elements were below the detection limit for either of the CLTs and are not shown. Another 8 of the 64 total trace elements are not shown because of failure of the ICP calibration Cumulative concentration from washed CLTs vs. cumulative concentration from continuous-flow CLTs. Points above the 1:1 line indicate that the cumulative concentration is higher for the washed CLT than the continuous-flow CLT. A total of 6 of 64 trace elements were below the detection limit for the continuous-flow CLTs and are not shown. A total of 8 of 64 trace elements are not shown because of failure of the ICP calibration

15 1. INTRODUCTION 14 Gray iron slags are byproducts created during melting of iron ore and/or scrap iron at foundries (van Ravenswaay 2000). In the molten state, impurities in the molten iron float to the surface, where they are skimmed off. When cooled and solidified, the skimmed-off material is called slag. The Wisconsin Department of Natural Resources (WDNR) reported that 1.08 million Mg of foundry sand and slag were produced in Wisconsin in 2000 (WDNR 2002). Of the foundry sand and slag produced, 45% was beneficially used. Much of the reuse consisted of daily cover material at landfills and some reuse was for geotechnical fill. Other potential uses include concrete aggregate, road base, railroad ballasts, ice control, and neutralization of industrial discharge and mine drainage (Apul et al. 2005). More applications are expected due to the growing emphasis on sustainable construction and reducing solid waste disposal costs. In such applications, there is concern that hazardous constituents in the foundry slag may be leached, causing pollution of soil and groundwater. Heavy metals and other toxic trace elements are of particular concern (Proctor et al. 2000). This report describes a leaching study conducted on five foundry slags from gray iron foundries located in Wisconsin. A natural sand from Wisconsin was also tested for comparison purposes. Batch water leach tests (WLTs) and column leach tests (CLTs) were conducted on each of the foundry slags. WLTs were conducted as a rapid and inexpensive assessment of leaching potential, whereas the CLTs were conducted to more closely simulate flow-through conditions that occur in the ground. CLTs were performed under continuous saturated flow at high and low flow rates, periodic flow with air circulation, and periodic flow with carbon dioxide circulation. The effects of washing the slag prior to testing were also investigated.

16 15 Concentrations from the WLTs and CLTs were compared to each other and to water quality standards. These standards include maximum contaminant levels (MCLs) in ground water stipulated by the United States Environmental Protection Agency (USEPA), groundwater quality standards stipulated by the State of Wisconsin (Chapter NR 140 of the Wisconsin Administrative Code), and maximum concentrations stipulated by the State of Wisconsin for beneficial use of industrial byproducts (Chapter NR 538 of the Wisconsin Administrative Code).

17 2. BACKGROUND Foundry Slag Foundry slag is the solid residual material that forms when the liquid impurities are skimmed off molten iron in a foundry. Materials used in the iron smelting process include iron ore or scrap iron, a fluxing agent (limestone or dolomite), and fuel (coke) (Lewis 1992). The composition of slag depends on the raw ingredients included in the molten metal. The major constituents are CaO, SiO 2, and Al 2 O 3 (Liu and Shih 2004), though MgO, MnO, and Fe 2 O 3 are also common. Slag also contains trace elements such as Ag, As, B, Ba, Be, Cd, Cr, Cu, Fe, Hg, Mo, Ni, Pb, Sb, Se, Ti, and Zn (Deng and Tikalsky 2006). Leaching of these trace elements is a source of concern when slag is reused in civil engineering applications. Slags are formed by air-cooling, water quenching (granulated), or mixing with controlled quantities of air, steam, or water (expanded) (Lewis 1992). Air-cooled slag is crystalline and vesicular due to trapped air bubbles during cooling (Lewis 1992). The angularity of crushed, air-cooled slag provides high friction and stability without cementing, making type this slag useful in fill applications. Air-cooled slag is also highly resistant to weathering and does not easily polish or wear smooth. Air-cooled slag has been used in asphalt concrete because of the high resistance to polishing. In 1992, road base material was the primary use of air-cooled slag (Lewis 1992). Quenching produces a glassy and granular slag (granulated slag) with little crystallization. Granulated slag has cementitious properties if an activator compound (i.e. calcium hydroxide) is combined with the slag (Lewis 1992). However, the majority of granulated slag has been used as fill material or concrete aggregate (Lewis 1992). Expanded slags, produced by adding controlled amounts of water, air, or steam, result in a vesicular and low density slag. A wide range of characteristics (including those of air-cooled and quenched slags) result from the many different methods available for

18 17 producing expanded slags. Expanded slags have mainly been used as light weight concrete aggregate, with better thermal insulation than many regular aggregates (Lewis 1992). 2.2 Previous Leaching Studies on Slags Proctor et al. (2000) conducted toxicity characteristic leaching procedure (TCLP) tests and WLTs on 11 blast furnace (iron) slags. Ba, Mn, and Zn were detected in 100% of the TCLP tests. As, Be, Cd, Cr, and Sb were also detected, but not in all TCLP tests. Of the trace elements analyzed, Be, Cr, Mn, Mo, and Se were the only trace elements reported at concentrations above background soil concentrations (Proctor et al. 2000). Trace elements detected in the WLTs included Al, As, Ba, Be, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, and Zn. Concentrations of Be, Cr, Mn, and Se were frequently reported above soil background concentrations (Proctor et al. 2000). However, no TCLP concentrations were above USEPA TCLP maximum contaminant concentrations (Proctor et al. 2000), indicating blast furnace slags should not be classified as hazardous waste. Deng and Tikalsky (2006) reported that leachate concentrations from slags (unspecified production method) did not exceed USEPA TCLP maximum contaminant concentrations using TCLP, synthetic precipitation leaching procedure, or ASTM D3987 (WLTs). However, slag bulk concentrations were found to exceed USEPA TCLP maximum contaminant concentrations, and further study of leaching from slags was recommended (Deng and Tikalsky 2006). Deng and Tikalsky (2006) reported that trace element concentrations in leachates from slag generally are less than 1% of the mass concentrations in slag. One explanation of the small quantity leached is that the trace elements in slag are embedded in the structure of the slag and are not readily extractable (Deng and Tikalsky 2006). Comparisons of leachate concentrations from foundry sand, dust, and slag found all three to leach at similar

19 18 concentrations, though the dust and slag had higher bulk concentrations. Deng and Tikalsky (2006) proposed that trace elements could be bonded to the slag particles (and dust and sand particles) and these bonded trace elements produce the concentrations observed in leachates. If similar quantities of trace elements are attached to foundry sand, dust, and slag, that may explain why higher leachate concentrations are not seen from materials with higher bulk concentrations (dust and slag). Proctor et al. (2000) calculated solid-water partition coefficients for each trace element from the WLT data. As and Sn were the only trace elements with partition coefficients below 1,000 L/kg, and were considered mobile in the aqueous phase (Proctor et al. 2000). Most of the trace elements exhibited increasing partition coefficients with increasing ph, except for Cr and Se, indicating that ph has an important impact on the leaching potential of steel slags. Adsorption of trace elements onto solids or surface precipitation may also be affected by the ph of the leachate, and affect leaching of trace elements from slag (Mayers et al. 2006). Water in a steel and iron slag dump located in the Lake Calumet region of Chicago, Illinois was tested for trace element concentrations. High concentrations of Ba, Cr, and Mn and lesser concentrations of 17 other trace elements were reported (Roadcap et al. 2005). Al and Zn were found in both suspended solids and dissolved phases. Concentrations of Al and Zn were 10 and 3 times higher in the suspend solids than the dissolved phase (Roadcap et al. 2005). For the same slag dump, Roadcap et al. (2005) reported many of the trace elements were embedded in silicate minerals, and the release of trace elements was affected by weathering of the matrix. Weathering of the slag produced suspended solids that were mobile, but were also found to settle. Particulate size was found to be a key factor in weathering. Coarser layers of slag allowed better circulation of air and water, thus increasing weathering (Roadcap et al. 2005). Introduction of carbon dioxide (CO 2 ) from

20 19 atmospheric air and infiltrating water was found to decrease the ph of the pore water. The additional H + ions can then react with zero valent iron to produce the mobile Fe 2+. Other metallic trace elements (i.e., Al, Cr, Mn, and Zn) can also be released from the slag as the slag weathers (Roadcap et al. 2005) Sparging with CO 2 and sparging with air were tested as remedial actions to reduce the ph of slag-impacted water. Sparging with CO 2 reduced the ph of a 900 ml water sample from over 11 to 7.0 in 10 minutes, whereas air sparging reduced the ph approximately 100 times slower (Roadcap et al. 2005). Air sparging also did not reduce the ph as much as CO 2 sparging, because of the equilibrium between atmospheric CO 2 and water. Toxicity testing using the Microtox procedure indicated that the toxicity of the air-sparged water dropped to less than 10% mortality, whereas untreated water had 100% mortality. CO 2 sparged water produced mortality rates 3 to 4 times greater than the air-sparged water (Roadcap et al. 2005). The Roadcap et al. (2005) study demonstrated that CO 2 and air can be used to alter the ph of slag impacted water. However, CO 2 produced more neutral ph water than air sparging, yet had a higher toxicity, indicating the toxicity is possibly impacted by both ph and trace element concentrations. As reported by Proctor et al. (2000), leaching of toxic trace elements commonly increases with decreasing ph. Thus, the lower ph in the CO 2 sparged water may have resulted in increased trace element concentrations and higher toxicity when compared to the air-sparged water.

21 3. MATERIALS Control Material A natural sand from Oconto County in northeastern Wisconsin was chosen as the control material for the column leach tests. The sand was air dried and passed through the No. 4 sieve prior to packing in the column. The sand is designated as poorly graded sand (SP) under the Unified Soil Classification System. All physical and chemical properties obtained for the sand are in Appendix A. 3.2 Gray Iron Foundry Slags Five gray iron foundry slags were collected from foundries in Wisconsin. The five slags are referred to as ARC, MAN, MTG, SHN, and WAB. The slags were passed repeatedly through a rock crusher until all the slag passed through a No. 4 sieve (4.75 mm). The crushed slag was then thoroughly mixed. Physical properties of the five slags and the sand are shown in Table 3.1. MTG slag is classified under the USCS as a SP, and all remaining slags are classified as well graded sand (SW). Particle size distribution curves for the five slags and the sand are shown in Figure 3.1. All slags are angular and contain glassy and rough, porous particles. The MAN and WAB slags contain rough, porous white particles, which are likely formed from the high SiO 2 content in these slags. The MTG slag is green in color, while the other slags are dark gray with the WAB slag having some white particles and the MAN slag having both white and green particles. Total elemental analysis (TEA) was conducted on each slag by the Wisconsin State Lab of Hygiene (WSLH) in Madison, Wisconsin. Digestion was conducted by USEPA Method 3050 and metals concentrations were determined using Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) following USEPA Method A summary of TEA results and Category 1 and 2 TEA criteria from Chapter NR 538 of the

22 21 Wisconsin Administrative Code are in Table 3.2. Concentrations exceeding Category 1 criteria are shown in BOLD and concentrations exceeding Category 2 criteria are indicated with an asterisk. Major chemical constituents for the ARC, MAN, and WAB slags are silica, aluminum oxide, and iron. Major constituents for the MTG and SHN slags are silica, aluminum oxide, iron, calcium oxide, and magnesium oxide. Minor constituents (less than 5%) for all slags include Cr, Mn, Ba, and other metal oxides (MeO). A summary of chemical compositions of the 5 slags is shown in Table 3.3. TEA and WLT concentrations must be considered when categorizing slags for Categories 1 and 2 in NR 538. The TEA and WLT concentrations are discussed in Section 5, as is the byproduct characterization.

23 4.0 METHODS WATER LEACH TESTS WLTs were conducted on each of the slags following ASTM D , Standard Test Method for Shake Extraction of Solid Waste with Water (ASTM 2006). A 70 g sample of slag was combined with 1,400 ml of Type II deionized water (ASTM D ) in a 2 L sealed container for a liquid-to-solid ratio of 20:1. The mixture was tumbled at 29 revolutions per minute for 18 h, following ASTM D After tumbling, the solution was filtered through a 0.45 µm filter. The filtered samples were preserved using metals-grade nitric acid to ph < 2 and stored in sealed 60 ml high-density polyethylene bottles at 4 o C prior to testing. WLTs were conducted on ARC, MAN, MTG, SHN, and WAB slags. The WLT leachates were analyzed for concentrations of Al, As, Ba, Be, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, Tl, and Zn. 4.2 COLUMN LEACH TESTS Continuous Flow Tests CLTs were conducted in cylindrical columns constructed from PVC tube having an inside diameter of 73 mm and a length of 450 mm (Figure 4.1). The columns were filled continuously from the bottom up with air-dried slag using a tremie tube to minimize sorting during filling. The slag was densified by tapping the side of the column until the top surface of the slag ceased to settle. More slag was added to the column after settling ceased and the column was again tapped until settling stopped. This process was repeated until no more slag could be added to the column. After filling, the mass of slag added to the column was measured, and the porosity of the column specimen was computed using the specific gravity of the slag and the dimensions of the column.

24 23 The CLTs were operated in an upflow mode using a constant flow rate applied with a peristaltic pump. Type II deionized water equilibrated with the atmosphere to ph 5 was used as the influent liquid. Photographs of columns in operation are shown in Figure 4.2 and Figure 4.3. The tests were conducted at a seepage velocity of 1 m/d, although a limited number of tests were conducted at 0.1 m/d to evaluate the affect of seepage velocity on leaching. Effluent from the CLTs was collected in evacuated Teflon sampling bags to minimize exposure to the atmosphere. Samples were initially collected every 0.1 pore volumes of flow (50-80 ml) for the first 2 pore volumes of flow (PVF) accumulated in the bag. After 2 PVF, the frequency was reduced to one sample per PVF. Each sample was immediately filtered through a 0.2 µm filter. Aqueous chemistry indicators (ph, redox potential or Eh, and electrical conductivity or EC) were measured, and then the sample was preserved for metals analysis using high purity nitric acid to ph < 2. The samples were stored in sealed 60 ml high-density polyethylene bottles at 4 o C prior to analysis Periodic Flow with Air Circulation Tests The effects of periodic saturation and de-saturation on leaching, as may occur from slags placed in the vadose zone, was evaluated by alternating deionized water and atmospheric air as the influent fluid. These columns were filled using the same procedure used for the continuous flow tests. One water-air cycle consisted of 36 h of water flow and effluent collection ( 3.5 PVF) followed by 30 h of air flow. The columns were drained from the influent port (bottom of the column) for 1 h before the air supply was connected to the influent port. Tests conducted with longer drainage times showed that drainage after 1 h was negligible. The water-air cycling was repeated 6 times, during which approximately 20 PV of water passed through each column. The air cycle was then expanded to

25 24 approximately 100 h of air flow. This extended water-air cycle was repeated 3 times and for an additional 10 PVF of water. Air for the columns was supplied from the compressed air system in the laboratory. A regulator was used to decrease the pressure prior to flowing the air through a humidifier. The air was humidified beforehand by sparging in a water filled chamber using a diffuser stone. A schematic of the humidifier is shown in Figure 4.4. Air from the humidifier was split into four tubes, with needle valves on each tube to control the flow into each column. A gas-bubble flow meter was connected to the effluent end of the column to check for the desired flow rate of 1 ml/min. At this flow rate, approximately 2 PV of air passed through the column in each 30 h gas phase of the water-air cycle. Leachate samples were collected at 0.3, 0.6, 1.2, 2.3, 3.4 PVF during each cycle (1 PVF 10.5 h of flow). A similar frequency of sampling was used in the intermittent wetting leaching experiments conducted by Sanchez et al. (2003) Periodic Flow with Carbon Dioxide Circulation Tests Tests similar to those with periodic air flow were conducting using CO 2 as the influent fluid during gas flow. These columns were filled using the same procedure as the continuous-flow columns and were conducted using the same cycling procedure as the periodic flow with air circulation tests. CO 2 for the columns was supplied from a compressed gas cylinder. As with the tests conducted with air, leachate samples were collected at 0.3, 0.6, 1.2, 2.3, 3.4 PVF during each cycle of water flow. The CO 2 was humidified beforehand by sparging in a water filled chamber using a diffuser stone. CO 2 from the humidifier was split into four tubes, and needle valves were installed on each tube to control the flow into each column. A gas-bubble flow meter was connected to the effluent end of the column to check for the desired gas flow (1 ml/min). At

26 25 this flow rate, approximately 2 PV of CO 2 passed through the column during each 30 h gas phase of the water-gas cycle. 4.3 CHEMICAL ANALYSIS Samples from the WLTs were analyzed for Al, As, Ba, Be, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, Tl, and Zn using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) at WSLH. The samples were digested using USEPA Method 3010 and analyzed following USEPA Method USEPA Method 9056 was followed for quality assurance. Effluent samples from the CLTs were analyzed for Ag, Al, As, Ba, Be, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, Tl, and Zn by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The procedure described in USEPA Method 6010 was followed using seven-point calibration curves prepared with High-Purity Standards calibration standards following USEPA Method Standard 6. Quality assurance consisted of running a continuing calibration verification (CCV), a continuing calibration blank (CCB), and a matrix spike (MSPK) or duplicate (DUP) sample every 10 samples. Multiple wavelengths for each trace element were analyzed to check for interference from spectra of other elements present in the samples. Two different ICP-OESs were used for analysis, a Perkin Elmer Optima 4300 DV and a Varian Vista MPX. Both instruments were optimized for maximum intensity readings on As 188 by changing the nebulizer and power settings. The Perkin Elmer ICP-OES was used to analyze samples from the continuous-flow tests. The Varian ICP-OES was used to analyze samples from the tests conducted to evaluate repeatability, the tests conducted at a slow flow rate, the periodic tests conducted with air or CO 2, and the tests conducted on washed slag.

27 26 Since more than one ICP-OES was used, more than one set of calibration curves was used and different detection limits (DLs) were determined. The DLs for Pb and Tl for the Perkin Elmer ICP-OES varied significantly between uses, so multiple DLs were used for Pb and Tl. Two sets of DLs are reported for the Varian ICP-OES because a repair was made to the instrument between uses. Summaries of detection limits and limits of quantitation (LOQ) are shown in Table 4.1.

28 5. WATER LEACH TEST AND TOTAL ELEMENTAL ANALYSIS RESULTS 27 Comparisons were made between concentrations from the WLTs, concentrations from the USEPA MCLs, and concentrations from the Wisconsin Administrative Code Chapter NR 140 (Groundwater Quality) and Chapter NR 538 (Beneficial Use of Industrial Byproducts) standards. The groundwater quality standards in Chapter NR 140 include preventative action limits (PALs) and enforcement standards (ESs). PALs are 2-10 times lower than the ESs, and are intended to be indicators of potential groundwater contamination. The NR 140 ESs are the same as the MCLs with additional standards for Ag, Fe, Mn, Ni, and Zn. Both the MCLs and NR 140 standards are for water quality with human health risk via consumption and/or exposure of primary concern. The combination of these two standards shall be referred to as ESs for simplicity. Water leach test concentrations are compared to NR 140 ESs in Table 5.1, with concentrations exceeding the standards shown in BOLD. Trace element concentrations from the WLTs do not exceed any of the USEPA MCLs. Concentrations in the leachates for the MAN, MTG, and SHN slags did not exceed NR 140 criteria. However, the Fe concentration for WAB slag and the Mn concentration for ARC slag exceed the ESs. The Fe concentration for the WAB slag is over 3 times greater than the ES, and the concentration of Mn for the ARC slag is nearly twice the ES. The concentration of Mn from WAB slag also exceeds the PAL, but not the ES. Water leach test concentrations are compared to Wisconsin Administrative Code Chapter NR 538 (Beneficial Use of Industrial Byproducts). Chapter NR 538 criteria require both WLTs and TEA for Category 1 and Category 2. Categories 3-5 do not require TEA. Materials meeting criteria under NR 538 qualify for different reuse applications depending on which category the material is classified as (Table 5.2).

29 28 WLT leachate concentrations are compared to NR 538 Category 1 criteria in Table 5.3, with concentrations exceeding Category 1 criteria shown in BOLD. Leachate concentrations were compared to Category 1 WLT concentration criteria because Category 1 criteria are the most stringent of the 5 categories. Mn concentrations from the ARC and WAB slags exceed Category 1 criteria and the Fe concentration from WAB slag also exceeds Category 1 criteria. None of the leachates from the slags tested in the WLTs exceed Category 2 & 3 for WLT concentration in NR 538. From only the WLTs concentrations, the MAN, MTG, and SHN slags are classified as Category 1 materials and the ARC and WAB slags are Category 2 materials. Concentrations from TEA (shown in Table 3.2) for all slags tested exceed NR 538 Category 1 criteria for As, Be, and Cr. MTG slag also exceeds Category 1 criteria for Tl and Category 2 criteria for Be. From the TEA alone, the ARC, MAN, SHN, and WAB slags can be classified as meeting Category 2 criteria. MTG slag does not meet Category 1 or Category 2 based on TEA and may be classified as Category 3, 4, or 5, which do not require TEA. The other 4 slags meet Category 2 TEA criteria. Chapter NR 538 requires both WLTs and TEA for classifying materials under Category 1 and Category 2. When TEA concentrations and WLT concentrations are both considered, no slag meets Category 1 criteria due to TEA concentrations exceeding the Category 1 TEA criteria. From the WLT concentrations, all materials could be classified as Category 2 materials. However, MTG slag exceeds the Category 2 criterion for Be and is classified as a Category 3 material. The ARC, MAN, SHN, and WAB slags are classified as Category 2 materials.

30 6. CLT RESULTS RELEASE PATTERNS Four types of release patterns were obtained from the column tests: first flush, delayed, steady-state, and no detection. Examples of first flush, delayed, and steady-state release patterns are shown in Figure 6.1. The first flush (FF) pattern is decreasing concentration over time (or PVF). The most common FF pattern is continuously decreasing concentrations approaching a steady-state near the DL. The delayed (D) release pattern is a low initial concentration followed by a gradual rise in concentration, and in some cases a fall in concentration at later times. The steady-state (SS) release pattern consists of concentrations remaining relatively constant throughout the test. The no detection (ND) release pattern occurs when all concentrations for the trace element are below the DL, and will not be discussed further. The first flush release pattern may be the result of readily available trace elements on the surface of the slag particles. The D pattern may be the result of competition among species or diffusion out of dead-end pores. Competition among species may be the result of ions with higher charge densities dissolving prior to lower charge density ions (Creek and Shackelford 1992); however, ph is likely the driving factor behind solubility of trace elements. Steady-state release may be the result of rate-limited solubility or concentrations at the solubility limit. However, higher effluent concentrations for the same trace element exist in the CLTs for other slags. This would indicate that the trace element has not reached the solubility limit, but may be limited due to competition between species. No tests have been conducted to rule out or support rate-limited solubility. Also, steady-state release commonly corresponds to concentrations between the DL and the limit of quantitation (LOQ), which is

31 30 approximately 3.3 times the DL. Thus, the steady-state release pattern could reflect limitations of the analytical method rather than a true release pattern. A summary of release patterns for all CLTs is presented in Table 6.1, and release patterns from the continuous-flow CLTs are summarized in Table 6.2. The ND release pattern was observed for 49% of the release patterns in the continuous-flow CLTs, which is 16% more than any other release pattern. The FF release pattern was observed for 33% of the release patterns and the D release pattern was observed for 11% of the release patterns. Other release patterns observed were SS (4%) and first flush changing to D (3%). The most common release patterns for the ARC slag were FF (44%) and ND (44%). No changes in release patterns for the ARC slag were observed in the repeatability tests. The most common release patterns for the MAN slag were ND (50%) and D (25%). The most common release pattern for the MTG slag was FF (83%). The most common release patterns for the sand were FF (42%) and ND (50%). The most common release pattern for the SHN slag was ND (67%). The most common release patterns for the WAB slag were ND (69%) and D (13%). Changes in release patterns were observed in the repeatability tests for the WAB slag. Zn was released in FF, D, and SS patterns. Fe was released in D and SS patterns. Pb and SS were released in SS and ND patterns. No explanation of the changes in release patterns could be determined from the data collected from the tests (i.e., ph and Eh). 6.2 AQUEOUS CHEMISTRY INDICATORS Leachates from all slags ranged in ph from approximately 6.8 to 10.7 for the continuous-flow CLTs. The average difference between minimum and maximum ph in a column is 1.7. A summary of ph, EC, and Eh measurements is shown in Table 6.3. The ph release patterns for the ARC, MTG, and SHN slags were D, the ph release pattern for the

32 31 MAN slag was FF, and the ph release pattern for the WAB slag was SS. Typical ph release patterns observed in the continuous-flow CLTs are shown in Figure 6.2. The EC in the continuous-flow CLTs ranged from 11 to 880 µs/cm for the ARC, MAN, and WAB slags and from 108 to 4,270 microsiemens per centimeter (µs/cm) for the MTG and SHN slags. The EC in leachates from all slags in the continuous-flow CLTs had a FF trend. Typical EC release patterns observed in the continuous-flow CLTs are shown in Figure 6.3. The FF release pattern is likely from readily soluble trace elements on the surface of the slag particles washing away with the first few PVF. The Eh ranged from -158 to 128 millivolts (mv) in the continuous-flow CLTs. The Eh of the ARC slag became more reducing, whereas the Eh of the MAN and SHN slags remained oxidizing throughout the test. The Eh of the MTG slag trended from oxidizing to reducing, and the Eh of the WAB slag became less reducing. Typical Eh release patterns observed in the continuous-flow CLTs are shown in Figure CONTINUOUS-FLOW CLT CONCENTRATIONS vs. NR 140 ESs Peak and cumulative concentrations of trace elements from the continuous-flow CLTs were compared to the ESs. Peak concentration is defined as the largest concentration observed in a sample collected during the CLT. Cumulative concentration (C c ) was calculated as n i i= 1 c = n ( C V ) i= 1 i i C (1) V where C i is the concentration (µg/l) of a particular trace element in sample i and V i is the volume of sample i in liters. Concentrations below the DL and above zero were included when calculating cumulative concentrations, because censoring introduces greater error

33 32 than inclusion of data below the DL (Berthouex and Brown 1994). Concentrations incorporated in the calculation for cumulative concentrations only include samples from the start of the CLT through the total number of PVF collected in the first continuous-flow CLT conducted on each slag. The cumulative concentration represents the flow-weighted average concentration for the test, and therefore may more accurately represent the longterm exposure used to determine the ESs. However, peak concentrations greatly exceeding ESs may also pose a health risk, as a single high-concentration dose may have significant health impacts and should not be ignored. Peak concentrations for the continuous-flow CLTs are summarized in Table 6.4, with BOLD font indicating concentrations above the ESs. For all the slags and the sand, peak concentrations from the continuous-flow CLTs for two or more trace elements exceeded the ESs. Peak Mn concentrations exceed the ES for all slag and the sand. Peak Tl concentrations exceed the ES for the ARC, MTG, and WAB slags and the sand. However, the Tl DLs for the MAN and SHN slags are above the ES. Therefore, whether or not Tl concentrations exceed the ES for MAN and SHN slags cannot be determined. Leachate from the sand exceeded both Mn and Tl ESs. For the sand, the peak Mn concentration was 334 µg/l and the peak Tl concentration was 5.4 µg/l. The ARC slag is the only slag to exceed the Fe ES. The MAN and MTG slags exceed the As ES. The Pb ES was only exceeded by the MTG slag. Se concentrations exceed the ES for the ARC, MTG, and SHN slags. Cumulative concentrations for the continuous-flow CLTs are summarized in Table 6.5. ARC and MTG are the only slags that have cumulative concentrations that exceed the ESs. Mn and Tl are the only trace elements that exceed the ESs. The cumulative concentration of Mn for MTG slag was 3,920 µg/l. Cumulative concentrations of Mn from all three ARC continuous-flow CLTs exceeded the ES. However, only one ARC

34 33 column had a cumulative concentration for Tl that exceeded the ES, and the average Tl concentration for the three CLTs is below the ES. This cumulative concentration for Tl was 2.2 µg/l, which is only slightly above the ES (2 µg/l). The cumulative concentration of Tl for the MTG slag was 18.6 µg/l. 6.4 CONTINUOUS-FLOW CLT CONCENTRATIONS vs. NR 538 CRITERIA Peak CLT concentrations from the continuous-flow tests are compared to NR 538 WLT concentration criteria in Table 6.6. Under continuous-flow conditions, every material tested except for the MAN and SHN slags had peak concentrations exceeding Category 3 criteria, yet no concentrations exceeded Category 4 criteria. Cumulative concentrations for the continuous-flow CLTs exceed Category 1 WLT concentration criteria for every slag. ARC and MTG slags are the only slags that produced leachate concentrations greater than Category 2 & 3 WLT concentration criteria. Cumulative concentrations are compared to NR 538 WLT concentration criteria in Table 6.7. Category 2 & 3 criteria were exceeded only for Mn (ARC and MTG slags) and Tl (MTG slag). Use of cumulative concentrations instead of peak concentrations from the CLTs reduced the frequency in which Category 2 & 3 concentration criteria were exceeded from 13 to 3, including the sand but not the repeatability tests conducted on the ARC and WAB slags (i.e., Mn exceeded regulations for ARC f-1, f-2 and f-3, but was counted once, not three times). 6.5 COMPARISON OF CLT CONCENTRATIONS TO WLT CONCENTRATIONS Peak CLT concentrations are compared to WLT concentrations in Figure 6.5, for CLT and WLT concentrations above the detection limits. All data except for one point fall above the 1:1 line, indicating that the peak CLT concentrations are nearly always greater

35 34 than WLT concentrations. All but three points fit between the 1:1 and 500:1 lines. The 30:1 line represents the centroid of the data, calculated using a geometric mean of the CLT concentrations divided by the WLT concentrations. The CLTs are designed to mimic flow-through conditions if the slag is placed in an environment with continuous water flow (i.e., below the water table) or is subject to periodic wetting and drying cycles due to precipitation events (vadose zone). Establishing a correlation between CLTs and WLTs would be advantageous, as WLTs are easier and quicker to conduct than CLTs. Concentrations from WLTs do not provide a good comparison to peak concentrations from CLTs, because the WLT concentrations represent a time/volume averaged concentration and the peak CLT concentrations represent a specific point in time. WLTs also incorporate effects from liquid-to-solid (LS) ratio and the peak CLT concentrations do not. A graph of cumulative CLT concentrations vs. WLT concentrations is shown in Figure 6.6. All of the data except four points fall between the 100:1 and 1:10 lines, with a centroid at the 4.3:1 line. Thus, cumulative concentrations from the continuous-flow CLTs are generally greater than WLT concentrations. Cumulative concentrations from the continuous-flow CLTs are 76% of the time greater than the WLT concentrations, and are on average 4.3 times higher than the WLT concentrations. Cumulative CLT concentrations are also higher than WLT concentrations, but the average concentrations are 7 times less than those of the peak CLT concentrations. Therefore, the cumulative CLT concentrations are more similar to WLT concentrations than peak CLT concentrations are to WLT concentrations. When cumulative concentrations are used instead of peak concentrations, LS ratios can be calculated for the CLTs. LS ratios were calculated for each continuous-flow CLT by dividing the total effluent volume collected for a column by the mass of the slag in the

36 35 column. The LS ratios for the continuous-flow CLTs ranged between 2.4:1 and 4.1:1 at the end of the tests. These LS ratios are 4.9 to 8.2 times lower than the LS ratios used in the WLTs (20:1), which is similar to the ratio of the cumulative CLT concentration to the WLT concentration (4.3:1). Higher cumulative concentration at lower LS ratios is consistent with the findings from Garrabrants et al. (2004), in which increases in trace element concentrations were observed with decreasing LS ratio. Cumulative CLT concentrations adjusted linearly to a LS ratio of 20:1 are compared to the WLT concentrations in Figure 6.7. The 0.66:1 line in Figure 6.7 passes through the centroid of the data. However, the linear adjustment may not accurately predict cumulative concentrations at greater LS ratios. For example, applying a linear adjustment of 5 to a particular cumulative CLT concentration is similar to saying that running the CLT out to a LS ratio of 20:1 is the same as repeating the same leaching pattern over again 5 times. This is not the case, as the leaching behavior will not repeat; rather the leaching behavior will likely continue the trend seen at the end of the CLT. Therefore, if a column leaches in a FF pattern, applying a linear adjustment may over estimate the cumulative concentration of the CLT at a LS ratio of 20:1. Linearly adjusting the CLT LS ratio is not an accurate method to use for adjusting CLT LS ratios to those of the WLTs. 6.6 REPEATABILITY OF THE CONTINUOUS-FLOW CLTs Three identical continuous-flow CLTs were conducted on the ARC and WAB slags to assess repeatability. Peak concentrations from each test were averaged and the maximum concentrations and minimum concentrations for each trace element were compared to the average concentration for each trace element. A histogram of the frequency of the ratios in intervals of 0.25 is in Figure 6.8. The mean of the ratios of the maximum concentration and minimum concentration to the average concentration is 1.8:1 when concentrations below the

37 36 detection limit are included. The standard deviation of the ratios is 2.4. The minimum ratio is 0.13:1 and the maximum ratio is 16:1. The ratios are also shown logarithmically transformed in Figure 6.9. The logarithmic transformation eliminates the arithmetic variation between the ratios and shows variation in terms of order of magnitude from the average concentration. The average of the variation in maximum magnitude (0.35) is slightly greater than the variation in minimum magnitude (-0.33). This is expected, as the variation in concentration on an arithmetic scale was greater for the maximum concentration ratios. However, the difference between the maximum magnitude ratios and the minimum magnitude ratios is significantly less than that for the arithmetic ratios. If concentrations below the DL are considered from the repeatability data, the mean of the ratios is 1.6:1 and the standard deviation is 1.8. A histogram of the frequency of the ratios in intervals of 0.25 is in Figure The reduction in variance from the average concentration and the reduction in standard deviation of these data likely results from the elimination of outlier data, most of which were from concentrations below the DLs. For example, Cd was not measured at concentrations above the DLs for the WAB slag in any of the repeatability CLTs. When DLs were not applied, the ratio of the maximum concentration to average concentration for Cd was 16:1, which was the largest ratio for all of the repeatability data. A line depicting the approximate concentrations of the DLs is shown on Figure 6.9. All data to the left of this line were not included in the statistical calculations for repeatability data with DLs applied. When only the concentrations from the second and third repetitions of the ARC and WAB tests are considered, the variation in concentration was reduced. The mean of the ratios from the second and third repetitions is 1.1:1 and the standard deviation is A histogram of the frequency of the ratios in intervals of 0.25 is in Figure The second

38 37 and third repetitions were the conducted at the same time, thereby limiting the variations in age of slag, leachant, calibration of analytical equipment, and analytical equipment used. The closer correlation between the second and third repetitions demonstrates that if tests are conducted on slags at the same time, leachate concentrations may vary less. Repeatability using the cumulative concentrations was also evaluated. A histogram of the frequency of the ratios in intervals of 0.25 is in Figure Repeatability of the CLTs using cumulative concentrations instead of peak concentrations was similar to the repeatability if DLs are applied. The mean of the ratios of the maximum concentration and minimum concentration to the average concentration is 1.5:1. The standard deviation of the ratios is 1.7. The minimum ratio is 0.18:1 and the maximum ratio is 11: CONTINUOUS FLOW WITH SLOW FLOW RATE CLTs CLTs were conducted with continuous flow at a seepage velocity (0.1 m/d) that was one-tenth that used in the continuous-flow CLTs to evaluate whether the rate of flow affected the leaching pattern or concentrations of trace elements leached from the slags. These tests, henceforth referred to as slow CLTs, were conducted on the ARC, MAN, SHN, and WAB slags. Results of these tests are summarized in Appendix B. Release patterns observed in the slow CLT leachates are summarized in Table 6.8, peak concentrations are summarized in Table 6.9, and cumulative concentrations are summarized in Table 6.10.

39 6.7.1 Release Patterns 38 Release patterns for all CLTs are summarized in Table 6.1, with major changes between CLTs shown in BOLD. Most of the release patterns (88%) were unaffected by flow rate. Major changes in release patterns were observed for Al (MAN slag), Fe (ARC slag), and Zn (MAN slag). Release of Fe from ARC slag changed from FF->D to D. The Fe release patterns at both flow rates were similar, but the high concentration of the first sample in the continuous-flow CLTs did not occur in the slow CLT. Release of Al from MAN slag changed from FF to D. However, release of Al from all other CLTs except the continuous-flow CLT followed a D pattern (all other slags were also commonly D release), indicating that the release pattern observed in the slow CLT is typical and the release pattern for the continuous-flow CLT probably is an anomaly Aqueous Chemistry Indicators The ph measured in leachates from all slags in the slow CLTs ranged from approximately 7.4 to The average difference between minimum and maximum ph in a column is 1.4. A summary of ph, EC, and Eh measurements is shown in Table 6.3. When comparing the slow CLTs to the continuous-flow CLTs, the differences between minimum ph measurements were on average 0.17 (range: to 0.33), the differences between maximum ph measurements were on average (range: to 0.21), and the differences between SS ph measurements were on average 0.10 (range: to 0.30). The ph release pattern for the ARC slag was D and the MAN, SHN, and WAB ph release patterns were FF. Typical ph release patterns observed in the slow CLTs are shown in Figure The SHN slag ph release pattern changed from D in the continuous-flow CLT to FF in the slow CLT, and the WAB ph release pattern changed from SS to FF.

40 39 The EC in the slow CLTs ranged from 14 to 685 µs/cm for the ARC, MAN, and WAB slags and from 124 to 2,860 µs/cm for the SHN slag. When comparing the slow CLTs to the continuous-flow CLTs, the differences between minimum EC measurements were on average µs/cm (range: to 11.4 µs/cm), the differences between maximum EC measurements were on average 111 µs/cm (range: -234 to 270 µs/cm), and the differences between SS EC measurements were on average 6.9 µs/cm (range: -3.0 to 11.3 µs/cm). The EC for all slags in the slow CLTs had a FF trend. Typical EC release patterns observed in the slow CLTs are shown in Figure The FF pattern likely is from readily soluble trace elements on the surface of the slag particles washing away with the first few PVF. No changes in the EC release patterns were observed between the continuous-flow CLTs and the slow CLTs. The Eh ranged from -189 to 157 mv in the slow CLTs. When comparing the slow CLTs to the continuous-flow CLTs, the differences between minimum Eh measurements were on average mv (range: -259 to 46.9 mv), the differences between maximum Eh measurements were on average 42.6 mv (range: to 133 mv), and the differences between SS Eh measurements were on average mv (range: -255 to 85.0 mv). The Eh of the ARC slag trended from oxidizing to reducing, the Eh of the MAN and SHN slags trended from reducing to oxidizing then back to reducing, and the Eh of the WAB slag trended from reducing to oxidizing. Typical Eh release patterns observed in the slow CLTs are shown in Figure The Eh release pattern for the MAN and SHN slags from the slow CLTs was reducing to oxidizing to reducing, whereas the Eh release patterns in the continuous-flow CLTs were SS oxidizing.

41 6.7.3 Peak Concentrations 40 Peak concentrations from the slow CLTs are compared to peak concentrations from the continuous-flow CLTs in Table The CLT yielding the higher peak concentration is labeled as slow for slow CLTs or fast for continuous-flow CLTs. If the peak concentrations are approximately equal (within the error associated with the analytical method) or are both below the LOQ, then same is reported. The LOQ was used as a limit for comparison because of the difficulty in reliably distinguishing concentrations falling between the DL and LOQ. For the slags where replicate column tests were conducted, averages of the peak concentrations from the replicates were used for comparison purposes. A graphical comparison of peak concentrations from the slow CLTs to peak concentrations from the continuous-flow CLTs is in Figure Concentrations below the DLs were not graphed. Points falling above the 1:1 line represent higher peak concentration due to the reduction in flow rate for the slow CLTs. Points below the 1:1 line indicate higher peak concentration from the continuous-flow CLTs than the slow CLTs. The calculated geometric mean is 0.44, indicating that on averaged the peak concentrations from the slow CLTs will be less than the peak concentrations from the continuous-flow CLTs. Peak concentrations from the slow CLTs were higher for 14% of the trace elements, and lower for 34% of the trace elements. Approximately 52% of the peak concentrations from the slow CLTs were the same as those from the continuous-flow CLTs. Nearly all of the occurrences of same resulted from peak concentrations for both tests being below the LOQ. Reduction of the seepage velocity resulted in minor increases in concentration (>2 fold increase) for Al (ARC, MAN, and SHN slags), Ba (ARC slag), and Zn (ARC, MAN, and SHN slags). A large decrease in concentration (approximately 100 fold decrease) was observed for Mn for SHN slag. Small decreases in concentration (<10 fold decrease) were observed for the

42 41 remaining trace elements. Ag, Be, Cd, Pb, and Sb had peak concentrations below the LOQ for both the slow and continuous-flow CLTs Cumulative Concentrations Cumulative concentrations from the slow CLTs are compared to cumulative concentrations from the continuous-flow CLTs in Figure Overall, 64% of the cumulative concentrations were lower for the slow CLTs, and no more than half of the trace elements eluted from each slag had higher cumulative concentrations for the slow CLTs. For the slow CLTs compared to the continuous-flow CLTs, cumulative concentrations for the slow CLTs were always higher for Ba and always lower for Be, Cd, Fe, Mn, Ni, and Se Comparison to Regulatory Standards Peak concentrations from the slow CLTs are compared to the ESs in NR 140 and the concentrations in NR 538 in Table No additional peak concentrations exceeded the ESs for the slow CLTs, and the number of trace elements with peak concentrations exceeding ESs dropped from 10 (continuous-flow CLTs) to 3 (slow CLTs). Mn (ARC and WAB slags) and Tl (ARC slag) are the only trace elements having peak concentrations that exceed the ESs for the slow CLTs. Mn (ARC slag) was the only element with a cumulative concentration that exceeded the ESs for the slow CLTs. Peak concentrations exceeding NR 538 criteria for the slow CLTs were compared to the peak concentrations exceeding NR 538 criteria for the continuous-flow CLTs. Reducing the flow rate did not increase the number of peak concentrations exceeding NR 538 criteria. As for the SHN and WAB slags are the only trace elements to exceed Category 1 concentration criteria for the slow CLTs, but not the continuous-flow CLTs. The number of

43 42 peak concentrations exceeding Category 2 & 3 criteria was reduced from 5 to 2 and the number of peak concentrations exceeding Category 1 criteria was reduced from 23 to 10. Cumulative concentrations from the slow CLTs compared to the concentrations in NR 538 are in Table Cumulative concentrations exceeding NR 538 criteria for the slow CLTs and continuous-flow CLTs have been compared. Reducing the flow rate did not increase the number of cumulative concentrations exceeding NR 538 criteria. As for SHN slag was the only additional cumulative concentration was found to exceed NR 538 Criteria. No cumulative concentrations were observed to be greater than Category 2 & 3 criteria for either CLT. Cumulative concentrations for 5 trace elements decreased below Category 1 criteria when the flow rate was reduced in the slow CLTs. Cumulative concentrations from the slow CLTs were also compared to the ESs and are shown in Table For the MAN, SHN, and WAB slags, the reduced seepage velocity did not affect whether cumulative concentrations exceeded the ESs. The cumulative concentration of Mn for the ARC slag exceeded the ES in the slow CLTs and the continuous-flow CLTs. The cumulative concentration of Tl for the ARC slag did not exceed the ES for the slow CLTs, but did exceed the ES for the continuous-flow CLTs. 6.8 PERIODIC FLOW WITH AIR CIRCULATION CLTs CLTs with periodic flow and air circulation (heretofore referred to as air CLTs) were conducted on the ARC, MAN, SHN, and WAB slags. Results of these tests are summarized in Appendix B. A summary of release patterns for the air CLTs is in Table Release Patterns Comparison of the air CLT release patterns in Table 6.15 and the patterns from the continuous-flow CLTs (Table 6.1) indicates that most of the release patterns (70%) did not

44 43 change when air was introduced. Moreover, for many cases where a change in pattern occurred, the change was minor. For example, a ND pattern changing to a SS pattern typically was caused by only a few samples having concentrations a few µg/l greater than the detection limit. In some cases a significant change in the release pattern occurred. These cases are denoted with BOLD text in Table 6.1. Major changes in the overall release patterns occurred for ARC slag (Se), MAN slag (Al and Zn), SHN slag (Se and Zn), and WAB slag (Se and Zn). For the ARC and SHN slags, Se release changed from FF in the continuous-flow CLTs to D (ARC slag) and SS (SHN slag) in the air CLTs (Figure 6.18), and in both cases introduction of air caused the Se concentration to increase or remain elevated compared to the continuous-flow CLTs. Zn leaching from the MAN slag changed from a D pattern to FF. However, this change in release pattern occurred before air was introduced in the air CLTs and cannot be directly attributed to the presence of air in the column. No explanation for the change in the Zn release pattern was apparent from the data collected from the CLT on SHN slag. Introduction of air also caused cycling of concentrations in eight cases (Table 6.15). An example of concentration cycling is shown for Al from the SHN slag in Figure This release pattern was classified as a D release with FF cycling, or D(C,FF) in Table 6.15, because a peak concentration occurred after the introduction of air, which was followed by a gradual decrease in concentration (i.e., a FF pattern within the cycle). A D leaching pattern also occurred during cycling in two cases (Table 6.15). Cycling was most common for Al, but also occurred for Ba, Fe, Mn, and Se.

45 6.8.2 Aqueous Chemistry Indicators 44 After introduction of air, the ARC, MAN, and WAB leachates ranged in ph from approximately 8.6 to 10.2 and the SHN slag ranged in ph from approximately 10.3 to The average difference between minimum and maximum ph in a column after introduction of air is 1.0, which is less than the difference for the continuous-flow CLTs (1.7). A summary of ph, EC, and Eh measurements is shown in Table 6.3. When comparing the air CLTs to the continuous-flow CLTs, the differences between minimum ph measurements were on average 0.28 (range: to 0.91), the differences between maximum ph measurements were on average 0.58 (range: 0.42 to 0.83), and the differences between SS ph measurements were on average 0.37 (range: to 1.0). The ph release pattern for the ARC slag was D, the MAN and WAB ph release patterns were FF, and the SHN ph release pattern was SS. Typical ph release patterns observed in the air CLTs are shown in Figure The ARC slag had D cycling within each period of continuous water flow. No other slags had consistent cycling trends. The ph release pattern for the SHN slag changed from D to SS and the WAB slag changed from SS to FF with the introduction of air. The EC ranged from 15 to 65 µs/cm for the ARC, MAN, and WAB slags and from 81 to 501 µs/cm for the SHN slag in the air CLTs. When comparing the air CLTs to the continuous-flow CLTs, the differences between minimum EC measurements were on average µs/cm (range: to 2.6 µs/cm), the differences between maximum EC measurements were on average 44.3 µs/cm (range: to 181 µs/cm), and the differences between SS EC measurements were on average µs/cm (range: to 7.3 µs/cm). The EC in leachates from all slags had a FF trend with FF cycling within each period of continuous water flow. Typical EC release patterns observed in the air CLTs are shown

46 45 in Figure The FF pattern likely is from readily soluble trace elements on the surface of the slag particles washing away within the first few PVF. The FF cycling may be the result of the introduced air altering the oxidation state of trace elements on the surface of the slag particles into more readily soluble species. The only changes in the EC release patterns were between the continuous-flow CLTs and the air CLTs was the addition of FF cycling for all slags. The Eh for the air CLTs ranged from -134 to 68.0 mv after the introduction of air. When comparing the air CLTs to the continuous-flow CLTs, the differences between minimum Eh measurements were on average mv (range: -132 to 154 mv), the differences between maximum Eh measurements were on average 34.4 mv (range: to 122 mv), and the differences between SS Eh measurements were on average 29.3 mv (range: to 122 mv). The Eh measurements for the ARC and SHN slags went from reducing to oxidizing after 3 to 6 periods of air flow in the columns. The Eh measurements for the MAN and WAB slags went from reducing to oxidizing immediately following the introduction of air in the columns. Typical Eh release patterns observed in the air CLTs are shown in Figure The Eh becoming oxidizing as the test continued results from the introduction of oxygen into the columns during the periods of air flow. The Eh release pattern changed to D reducing to oxidizing for the ARC, MAN, and SHN slags. The Eh release pattern did not change for the WAB slag, but the maximum Eh measured increased when compared to the continuous-flow CLTs. FF cycling was observed for all slags in the air CLTs Peak Concentrations Peak concentrations from the air CLTs are compared to peak concentrations from the continuous-flow CLTs in Table 6.16 and Table 6.9. The CLT yielding the higher peak

47 46 concentration is labeled as air for air CLTs or fast for continuous-flow CLTs. If the peak concentrations are approximately equal or are both below the LOQ, then same is reported. The LOQ was used as a limit for comparison because of the difficulty in reliably distinguishing concentrations falling between the DL and LOQ. For the slags where replicate column tests were conducted, averages of the peak concentrations from the replicates were used for comparison purposes. A graphical comparison of peak concentrations from the air CLTs to peak concentrations from the continuous-flow CLTs is in Figure Concentrations below the DLs are not included in the graph. Points falling above the 1:1 line represent higher peak concentration due to the introduction of air in the CLTs. Points below the 1:1 line indicate higher peak concentration from the continuous-flow CLTs than the air CLTs. Most of the peak concentrations for the air CLTs were within an order of magnitude of the peak concentrations from the continuous-flow CLTs. When the air CLTs were compared to the three continuous-flow CLTs, no difference in the percentage of trace elements exceeding the one order of magnitude range was observed. On average, peak concentrations from the air CLT were approximately the same as those of the continuous-flow CLTs (geometric mean of the air CLTs divided by the continuous-flow CLTs is 0.9). However, peak concentrations in the air CLTs did decrease (Mn) or increase (Tl) for specific trace elements. One-half (50%) of the peak concentrations from the air CLTs were approximately the same as those from the continuous-flow CLTs. Higher peak concentrations for the air CLTs occurred for 20% of the trace elements, and lower peak concentrations for the air CLTs occurred for 30% of the trace elements. The majority of the 50% of the trace elements labeled as same had concentrations below the LOQ. Peak concentrations of Pb from the air CLTs were higher than the continuous-flow CLTs, and peak concentrations of Al were either the same or higher. Introduction of air reduced Mn and Zn peak concentrations when

48 47 compared to the continuous-flow CLTs. All other trace elements varied between higher and lower peak concentrations for the air CLTs. The number of trace elements in leachate from the ARC and MAN slags that increased in concentration was approximately the same as the number that decreased in concentration, as demonstrated in Table In contrast, peak concentrations in leachates from the SHN and WAB slags generally decreased as a result of the introduction of air to the CLTs. Additionally, introduction of air generally did not affect peak concentrations of trace elements that had peak concentrations below the LOQ or DL (Ag, Be, Cd, Cr, Pb, and Sb) when tested under continuous flow. The exception was for Tl, where peak concentrations exceeded DLs in all of the air CLTs, but were not above DLs for the continuous flow CLTs conducted on the MAN and SHN slags. However, peak concentrations of Tl for the MAN, SHN, and WAB slags were below the LOQ. Thus, comparisons of peak concentrations of Tl between CLTs could not be made for the MAN, SHN, and WAB slags. Peak concentrations of Mn and Zn from all of the continuous-flow CLTs were greater than peak concentrations from the air CLTs. Al peak concentrations were greater in the air CLTs, except for the CLTs conducted on WAB slag. Peak concentrations occurring prior to air introduction were not influenced by air and are likely the result of variation in the slag, whereas peak concentrations occurring after introduction of air may be affected by the air. Peak concentrations that occurred after the introduction of air are: Ag, Al, As, Cu, and Sb for ARC slag, Ag, Al, As, Cu, Fe, Mn, Pb, and Se for MAN slag, Al, Ba, Cu, Fe, Sb, Se, and Tl for SHN slag, and Al, As, Cu, Fe, Pb, Se, Tl, and Zn for WAB slag. Additionally, Be, Cd, and Cr were not detected in the air CLTs.

49 6.8.4 Cumulative Concentrations 48 Cumulative concentrations from the air CLTs are compared to cumulative concentrations from the continuous-flow CLTs in Figure 6.24 and Table Points falling above the 1:1 line represent higher cumulative concentration due to the introduction of air in the CLTs. Points below the 1:1 line indicate higher cumulative concentration from the continuous-flow CLTs than the air CLTs. Introduction of air resulted in higher cumulative concentrations for 12 of 16 trace elements for the ARC slag, 7 of 12 trace elements for the MAN and SHN slags, and 8 of 16 trace elements for the WAB slag. Cumulative concentrations for the remaining elements were lower for the air CLTs than the continuousflow CLTs. However, nearly all of the concentrations from the air CLTs are within an order of magnitude of those from the continuous-flow CLTs. When the air CLTs were compared to the three continuous-flow CLTs (ARC and WAB slags), three trace elements from the air CLTs had cumulative concentrations greater than one order of magnitude higher than the continuous-flow CLTs. Higher cumulative concentrations were obtained from the air CLTs for 61% of the trace elements that were examined. In particular, air circulation increased the cumulative concentrations of Ag and Se for all slags and increased the cumulative concentration for As, Fe, and Pb for 3 of 4 slags. Cd and Cr were the only trace elements that consistently decreased in cumulative concentration with the introduction of air. The air cycles introduced oxygen to the slag, and likely resulted in oxidation of the surfaces of the slag particles. The presence of an oxidized layer on the slag particles may have inhibited leaching by reducing the surface area over which leaching can occur. A reduced leaching area would restrict the leaching of trace elements from the surface of the slag particles, thus reducing peak concentrations. Because the readily leached trace elements on the surfaces of the slag particles were not leached, the chemical gradient between the slag surface and the water in the pore spaces would be higher than if the

50 49 surfaces had been exposed for leaching (continuous-flow CLTs). The greater chemical gradient could maintain a steadier rate of leaching, which may have resulted in higher cumulative concentrations Comparison to Regulatory Standards Peak concentrations from the air CLTs are compared to the ESs in NR 140 and the concentrations in NR 538 in Table Concentrations exceeding the ESs are shown in BOLD. Concentrations exceeding Category 1 criteria are shown in BOLD and concentrations exceeding Category 2 & 3 criteria are indicated with an asterisk. Introduction of air had no effect on whether peak concentrations exceeded the ESs for the ARC and WAB slags. However, introduction of air resulted in peak concentrations of As and Mn dropping below the ESs, and the peak Tl concentration falling above the ES for MAN slag. For SHN slag, the peak Sb concentration exceeds the ES and the peak Mn concentration does not exceed the ES, though it did in the continuous-flow CLTs. Cumulative concentrations from the air CLTs are shown with the NR 538 criteria in Table Cumulative concentrations from the air CLTs exceeding Category 1 criteria are shown in BOLD. All trace elements with cumulative concentrations exceeding Category 1 criteria for ARC and SHN under continuous-flow conditions also exceeded Category 1 criteria for the air CLTs. Air circulation resulted in cumulative concentrations of Se exceeding Category 1 criteria for all slags, whereas cumulative concentrations of Se did not exceed Category 1 criteria under continuous flow. Additionally, cumulative concentrations of Tl for the SHN and WAB slags exceed Category 1 criteria. Cumulative concentrations of Mn for the MAN and WAB slags and As for MAN exceeded Category 1 for the continuous-flow CLTs, but do not in the air CLTs. The cumulative concentration of Mn for the ARC slag also exceeded the Category 2 & 3 criteria for both the air CLTs and the continuous-flow CLTs.

51 50 Cumulative concentrations from the air CLTs were also compared to the ESs and are shown in Table For the SHN and WAB slags, introduction of air into the CLTs did not affect whether cumulative concentrations exceeded the ESs. The cumulative concentrations of Mn and Tl for the ARC slag exceeded the ESs in the air CLTs and the continuous-flow CLTs. However, cumulative concentration of Tl for the MAN slag exceeded the ES for the air CLTs, but not for the continuous-flow CLTs. 6.9 PERIODIC FLOW WITH CARBON DIOXIDE CIRCULATION CLTs CLTs with periodic flow and CO 2 circulation (heretofore referred to as CO 2 CLTs) were conducted on the ARC, MAN, SHN, and WAB slags. Results of these tests are summarized in Appendix B. Release patterns observed in the CO 2 CLT leachates are summarized in Table 6.20 with major changes in release patterns shown in BOLD Release Patterns Release patterns for all CLTs are summarized in Table 6.1. The addition of CO 2 in the CLTs resulted in 59% of the release patterns being different than those observed in the continuous-flow CLTs. The major changes were a transition from FF (continuous-flow CLTs) to D (CO 2 CLTs) for Ba (WAB slag), Mn (SHN slag), and Tl (MAN slag), a transition from FF to D for Mn (SHN slag), and a transition to ND for Al (all slags) after introduction of CO 2. The most significant change occurred for Al, which typically was released in a D pattern, but dropped below the detection limit when CO 2 was introduced (Figure 6.25). This drop in Al concentration was most likely caused by a change in ph, which dropped from to after introduction of CO 2. In this ph range, Al normally exists as Al 2 O 3 (H 2 O)(s) regardless of Eh (Takeno 2005). Al concentrations remained below the

52 51 detection limit and the ph remained between 5.5 and 8.0 for the remainder of the CO 2 CLTs. Aside from the drop-off in Al concentrations seen for all slags, the Al release pattern for MAN slag changed from FF in the continuous-flow CLTs to D prior to CO 2 introduction. Other major changes in release patterns occurred for Ag, Al, Ba, Cd, Cr, Mn, Ni, Sb, Tl, and Zn. Fe and Mn exhibited strong cyclic release patterns, with concentrations rising substantially after each period of CO 2 flow. An example of this pattern for Fe leaching from ARC slag is shown in Figure Cycling patterns were also observed in the release patterns for Ag, As, Ba, Cd, Cr, Ni, Pb, Sb, Tl, and Zn. Cycling is likely linked to the cycling patterns observed in the ph and Eh measurements. The Mn release pattern for SHN slag was the only FF release of Mn for SHN slag, as Mn was released in a D pattern for the other CLTs. The only time Ag was detected in leachates from CLTs was during the CO 2 CLTs. The cycling release pattern was likely caused by a chemical reaction between the wet slag and the CO 2, producing more mobile or readily soluble compounds on the surface of the slag particles. The cycling release patterns (generally higher concentrations immediately following CO 2 flow) may have resulted from the reduction in ph observed after each period of CO 2 flow, as many trace elements are more soluble at lower ph. Figure 6.27 is an example of the cycling pattern observed for ph and Eh for the ARC slag. The reduction in ph was most likely caused by the dissolution of CO 2 into the moisture in the pore spaces of the columns. Higher partial pressures of CO 2 decreases the ph of the solution (Benjamin 2002), and the partial pressure of CO 2 in the CO 2 CLTs was high, as 100% CO 2 gas was used in the tests.

53 6.9.2 Aqueous Chemistry Indicators 52 After CO 2 introduction, the ARC, MAN, and WAB leachates ranged in ph from approximately 6.6 to 8.9 and the SHN slag ranged in ph from approximately 5.1 to 7.0. The average difference between minimum and maximum ph in a column after introduction of CO 2 is 2.4, which is higher than the difference for the continuous-flow CLTs (1.7). A summary of ph, EC, and Eh measurements is shown in Table 6.3. When comparing the CO 2 CLTs to the continuous-flow CLTs, the differences between minimum ph measurements were on average (range: to -2.62), the differences between maximum ph measurements were on average (range: to -1.17), and the differences between SS ph measurements were on average (range: to -2.25). For the CO 2 CLTs, the ph release pattern for the ARC was D, the MAN and WAB ph release patterns were SS, and the SHN ph release pattern was FF. All release patterns also had D cycling within each period of continuous water flow. Typical ph release patterns observed in the CO 2 CLTs are shown in Figure The reduction in ph for all slags can be attributed to the formation of carbonic acid in the water in the pore spaces during CO 2 flow. The ph release pattern for the SHN slag changed from D to FF and the ph release pattern for the MAN slag changed from FF to SS with the introduction of CO 2. For the CO 2 CLTs, the EC ranged from 73.5 to 567 µs/cm for the ARC, MAN, and WAB slags, and the EC ranged from 215 to 2,100 µs/cm for the SHN slag. The highest EC measured for the MAN slag was immediately following the first introduction of CO 2. When comparing the CO 2 CLTs to the continuous-flow CLTs, the differences between minimum EC measurements were on average 59.6 µs/cm (range: 46.0 to 90.5 µs/cm), the differences between maximum EC measurements were on average 816 µs/cm (range: 475 to 1,780 µs/cm), and the differences between SS EC measurements were not determined because a SS condition was not established by the end of the test due to cycling.

54 53 The EC in leachates from all slags had a FF trend with FF cycling within each period of continuous water flow. Typical EC release patterns observed in the CO 2 CLTs are shown in Figure The FF cycling pattern likely results from the reduced ph after each CO 2 introduction, which increases solubility of most elements. The only changes in the EC release patterns were between the continuous-flow CLTs and the CO 2 CLTs was the addition of FF cycling for all slags. The highest EC was measured prior to introduction of CO 2 for the ARC, SHN, and WAB slags. After the introduction of CO 2 in the CO 2 CLTs, the Eh ranged from -106 to 12.4 mv. When comparing the CO 2 CLTs to the continuous-flow CLTs, the differences between minimum Eh measurements were on average mv (range: -175 to 44.1 mv), the differences between maximum Eh measurements were on average mv (range: to 53.3 mv), and the differences between SS Eh measurements were on average mv (range: -160 to 57.3 mv). The Eh of the ARC slag trended from reducing to oxidizing, the MAN and WAB slags trended from reducing to neutral, and the Eh of the SHN slag became more reducing by the end of the tests. Typical Eh release patterns observed in the CO 2 CLTs are shown in Figure Delayed cycling was observed for the ARC and WAB slags, FF cycling was observed for the SHN slag, and no repeated cycling pattern was observed for the MAN slag. The Eh release pattern for the ARC slag changed from FF reducing to D reducing and the Eh release pattern for the MAN slag changed from SS oxidizing to D reducing with the addition of CO 2. The Eh release pattern for the SHN slag changed from SS oxidizing to FF reducing with the introduction of CO 2.

55 6.9.3 Peak Concentrations 54 Peak concentrations from the CO 2 CLTs are compared to peak concentrations from the continuous-flow CLTs in Table 6.21 and Table 6.9. The CLT yielding the higher peak concentration is labeled as CO 2 for CO 2 CLTs or fast for continuous-flow CLTs. If the peak concentrations are equal or both peak concentrations are below the LOQ, then same is reported. The LOQ was used as a limit for comparison because of the difficulty in reliably distinguishing concentrations falling between the DL and LOQ. For the slags where replicate column tests were conducted, averages of the peak concentrations from the replicates were used for comparison purposes. Approximately 45% of the peak concentrations from the CO 2 CLTs were the same as those from the continuous-flow CLTs. Peak concentrations from the CO 2 CLTs were higher for 41% of the trace elements, and lower for 14% of the trace elements. Nearly all of the occurrences of same resulted from peak concentrations for both tests remaining below the LOQ. However, in these cases, peak concentrations from the CO 2 CLTs were often above the detection limit, whereas peak concentrations from the continuous-flow CLTs were below the detection limit. Of the 55% of trace elements for which the peak concentration changed when CO 2 was introduced, Al was the only trace element for which peak concentrations for all slags increased or peak concentrations for all slags decreased. Except for Al, both increases and decreases in peak concentration for the same trace element were not observed and were changes in peak concentration were either approximately the same or increased, or approximately the same or decreased. A graphical comparison of peak concentrations from the CO 2 CLTs to peak concentrations from the continuous-flow CLTs is in Figure Peak concentrations below DLs were not graphed. Points falling above the 1:1 line represent higher peak concentration due to the introduction of CO 2 in the CLTs. Points below the 1:1 line indicate higher peak

56 55 concentration from the continuous-flow CLTs than the CO 2 CLTs. The calculated geometric mean of the CO 2 CLT peak concentrations divided by the peak continuous-flow CLT concentrations is 6.0, indicating that on average, introduction of CO 2 increased peak concentrations when compared to the continuous-flow CLTs. Introduction of CO 2 caused large increases in concentration (>100 fold increase) for Fe and Mn (all slags) and small increases in concentration (<10 fold increase) for Ba (ARC and WAB slags), Ni (ARC and WAB slags), Pb (MAN, SHN, and WAB slags), Tl (all slags), and Zn (all slags). Small decreases in concentration (<10 fold decrease) were observed for As (MAN slag), Cr (ARC slag), Cu (WAB slag), and Se (ARC, MAN, and SHN slags). Peak concentrations occurring prior to CO 2 introduction were not influenced by CO 2 and are likely the result of variation in the slag. Prior to the introduction of CO 2, peak concentrations occurred for 8 trace elements (Ag, Al, Cr, Sb, Se, Tl, and Zn) for ARC slag, 2 trace elements (Al and Sb) for MAN slag, 3 trace elements (Al, Pb, and Se) for SHN slag, and 5 trace elements (Al, As, Cu, Sb, and Zn) for WAB slag. However, concentrations were higher in the CO 2 CLTs compared to the continuous-flow CLTS after CO 2 introduction for Ag, Cr, Tl, and Zn (ARC slag) and As and Zn (WAB slag). Concentrations were lower in the CO 2 CLTs compared to the continuous-flow CLTS after CO 2 introduction for Al (all slags) and Se (ARC and SHN slag). The remaining 5 trace elements were below the DLs after introduction of CO 2. The high concentrations of Mn measured in the CO 2 CLTs are likely the result of the reduction in ph caused by introduction of CO 2. For a system rich in CO 2 and Mn, Mn 2+ will dominate at the Eh range seen in the CO 2 CLTs (-150 to 25 mv) and at a ph less than 7.5 (Stumm and Morgan 1996). At ph between 7.5 and 11.5 (and the Eh range in the CO 2 CLTs) the solid MnCO 3 dominates the system. For all slags, as each water cycle progresses towards completion, the ph of the leachate increases and the Mn concentration decreases. For slags in which the maximum ph in each cycle increases as the test

57 56 continues (ARC, MAN, and WAB slags), the maximum Mn concentration in each cycle decreases. For the SHN slag, the overall ph trend is decreasing, and the maximum Mn concentrations in each cycle increase as the test continues. Because the opposite ph and Mn concentration relationships occur between the ARC, MAN, and WAB slags and the SHN slag, but the same cycling behavior occurs for all slags, the Mn concentration in the CO 2 CLTs is dependant on ph. Periodic flow is not considered a major source for the cycling trend or the increase in Mn concentration observed, as only one slag (WAB) showed cycling behavior in the air CLTs. Peak Mn concentrations in the air CLTs were comparable or lower than concentrations measured in other CLTs. The high concentrations of Fe are likely due to the decrease in ph caused by the introduction of CO 2. For the Eh-pH conditions in leachate from the CO 2 CLTs (Eh = -150 to 25 mv, ph = 5.5 to 8.0), Fe 2+ is the dominant species, and solid forms (i.e. Fe 2 O 3 ) become dominant for ph between 9.1 and 12.8 (Benjamin 2002). The solids FeCO 3 and Fe(OH) 3 dominate in a system with CO 2 at ph between 7 and 8 and the Eh conditions measured in the CO 2 CLTs (Stumm and Morgan 1996). Thus, a reduction in ionic Fe (Fe 2+ ) is observed as the ph of the system increases. This relationship between ph and ionic trace element and solid species is similar to and can be explained using the same reasoning as that for Mn. Adsorption of trace elements onto Fe compounds as ph increases is a likely cause for the decreases in concentration of other trace elements as ph increases throughout the test and during each cycle. Zn and Cd are removed from solution due to sorption onto Fe(OH) 3 (s) (Benjamin 2002) and Cd, Cu, Ni, Pb, and Zn adsorb onto Fe(OH) to approximately 100% (Younger et al. 2002) with increasing ph. Trace elements such as Zn also adsorb onto CaCO 3 as ph increases from 6.5 (0% adsorption) to 9.5 (>90% adsorption). Systems with greater partial pressures of CO 2 exhibit greater adsorption at the

58 57 same ph as systems with smaller partial pressures of CO 2 (Stumm 1992). Adsorption of Cr 3+ onto Fe(OH)(s) increases to approximately 100% by ph 4 (Younger et al. 2002), thereby virtually eliminating Cr 3+ from the leachates in all slag CLTs because the lowest ph measured in this study was 5.1. Solubility of trace elements at different ph may also play an important role in concentrations measured in the leachates. For example, the solubility of Cu 2+, Fe 2+, and Zn 2+ decrease with increasing ph (Younger et al. 2002). The solubility of Cu 2+ drastically decreases at ph 6 and remains low as ph increases (Stumm and Morgan 1996). The solubility of Zn is minimized at ph between 8.5 and 11 (Stumm and Morgan 1996), which encompasses the steady-state ph values observed for all slag CLTs except the CO 2 CLTs. The concentrations of Zn measured in the CO 2 CLTs may be consistently higher in each sample than those measured in other CLTs, because the solubility of Zn is greater and adsorption of Zn onto solids is less at lower ph Cumulative Concentrations Cumulative concentrations from the CO 2 CLTs are summarized in Table Cumulative concentrations from the CO 2 CLTs are compared to cumulative concentrations from the continuous-flow CLTs in Figure Points falling above the 1:1 line represent higher cumulative concentration due to the introduction of CO 2 in the CLTs. Points below the 1:1 line indicate higher cumulative concentration from the continuous-flow CLTs than the CO 2 CLTs. Comparison of the cumulative concentrations from the CO 2 CLTs to those from the continuous-flow CLTs (Table 6.10) indicated that 77% of the cumulative concentrations for the CO 2 CLTs were higher than the cumulative concentrations from the continuous-flow CLTs. Introduction of CO 2 increased cumulative concentrations for 13 of 16 trace elements

59 58 for the ARC and WAB slags, 8 of 12 trace elements for the MAN slag, and 9 of 12 trace elements for the SHN slag. Large increases in concentration were observed for Fe and Mn (>100 fold), modest increases were observed for Cr and Ni ( fold), and small increases were observed for Ag, Ba, Cd, Sb, and Zn (<10 fold) (Figure 6.32). Small decreases in cumulative concentration (<10 fold) were observed for Al and Se (Figure 6.32) Comparison to Regulatory Standards Peak concentrations from the CO 2 CLTs are compared to the ESs in NR 140 and the concentration criteria in NR 538 in Table Peak concentrations of 19 trace elements (4 Fe, 4 Mn, 2 Pb, 4 Sb, 1 Se, and 2 Tl) exceeded the ESs. Cumulative concentrations exceeded the ESs for 9 trace elements (3 Fe, 4 Mn, 1 Sb, and 1 Tl) and are shown in BOLD in Table Cumulative concentrations compared to the concentrations in NR 538 are in Table Introduction of CO 2 resulted in peak concentrations of 11 trace elements exceeding the ESs that did not exceed the ESs for the continuous-flow CLTs and 2 trace elements with peak concentrations that fell below the ESs for the CO 2 CLTs, but exceeded the ES for the continuous-flow CLTs. Peak concentrations of Fe (MAN, SHN, and WAB slags), Pb (SHN and WAB slags), Sb (all slags), and Tl (MAN and SHN slags) exceeded the ESs for the CO 2 CLTs but not the continuous-flow CLTs. Se (ARC slag) and As (MAN slag) had peak concentrations below the ESs for the CO 2 CLTs but above the ESs for the continuous-flow CLTs. All cumulative concentrations that exceeded the ESs for the continuous-flow CLTs (Mn and Tl for the ARC slag) also exceeded the ESs for the CO 2 CLTs. Cumulative concentrations of Fe (ARC, MAN, and WAB slags), Mn (MAN, SHN, and WAB slags), and Sb (SHN slag) exceeded the ESs for the CO 2 CLTs, but did not exceed the ES for the continuous-flow CLTs.

60 59 Differences in cumulative concentrations exceeding NR 538 concentration criteria between the CO 2 CLTs and continuous-flow CLTs have been compared. A total of 17 trace elements had concentrations exceeding NR 538 concentration criteria in the CO 2 CLTs. Category 4 concentration criteria were exceeded by 3 trace elements and Category 2 & 3 concentration criteria were exceeded by 4 more trace elements. Category 1 concentration criteria were exceeded by 9 more trace elements (Cd, Fe, Mn, Sb, and Tl) and 2 less trace elements (Al and As) in the CO 2 CLTs compared to the continuous-flow CLTs. The Category 4 concentration criterion was exceeded by Fe (ARC, MAN, and WAB slags), which are the only occurrences of Category 4 concentration criteria being exceeded. Category 2 & 3 concentration criteria exceeded are Fe (ARC, MAN, and WAB slags) and Mn (all slags). Cumulative concentrations of Cd (ARC, MAN, and WAB slags), Fe (ARC, MAN, and WAB slags), Mn (SHN slag), Sb (SHN slag), and Tl (SHN slag) exceeded Category 1 concentration criteria for the CO 2 CLTs but not the continuous-flow CLTs. Al (SHN slag) and As (MAN slag) were the only trace elements that did not exceed NR 538 concentration criteria for the CO 2 CLTs, but did for the continuous-flow CLTs. Cumulative concentrations from the CO 2 CLTs were also compared to the ESs and are shown in Table Introduction of CO 2 into the CLTs affected whether cumulative concentrations exceeded the ESs for all slags. All trace elements that exceeded ESs in the continuous-flow CLTs also exceeded ESs in the CO 2 CLTs. The cumulative concentrations of Mn and Tl for the ARC slag exceeded the ESs in the CO 2 CLTs and the continuous-flow CLTs. Additional trace elements exceeding ESs in the CO 2 CLTs but not the continuousflow CLTs are Fe (ARC, MAN, and WAB slags), Mn (MAN, SHN, and WAB slags), and Sb (SHN slag).

61 6.10 WASHED SLAG CLTs WITH CONTINUOUS FLOW 60 Washing of slag was evaluated as a means to reduce leachate concentrations, particularly for trace elements that exceed groundwater quality standards described in Section NR 140 of the Wisconsin Administrative Code. Tests were conducted on 4-kg samples of the ARC, MAN, SHN, and WAB slags. Each sample was divided into 5 sub-samples that were washed over a No. 100 sieve using 5 L of tap water from Madison, WI. The water was applied in 0.5-L increments as the slag was shaken back and forth on the sieve until water ceased to flow out of the slag. The slag was then air dried for 3 d after washing. The columns could not be filled with the washed slag using the procedure used for the other CLTs because moisture in the slag prevented the slag from flowing through the tremie. Thus, the columns were filled with a scoop and the slag was densified by tapping and vibrating the column. As the slag settled, more slag was added until no more slag could be added. Column tests were then conducted using the same procedures employed for the continuous flow CLTs Release Patterns Release patterns for the washed CLTs are summarized in Table 6.25, and release patterns for all CLTs are summarized in Table 6.1. The most common release patterns observed for the washed CLTs were ND and SS. Comparison of the release patterns from the washed CLTs and the continuous-flow CLTs indicated that 36% of the release patterns changed. The majority of the changes in release patterns involved the release patterns changing to or changing from SS or ND with washing the slag prior to placement in the columns. Changes in release patterns were observed for each of the slags. The Al release pattern changed from FF to D for MAN slag. The Ba release pattern changed from FF to D

62 61 for WAB slag. The Mn release pattern changed from FF to D for the ARC slag and from D to FF MAN slag. The Se release pattern changed from FF to D for SHN slag. The release pattern change from FF to D may be the result of washing away of small, high surface area particles and kinetic limitations in the larger particles. Conceptual examples of the small, readily leachabe particles; large, kinetically limited particles; and the combination (total leaching) of small, readily leachable particles and large, kinetically limited particles are show in Figure If the small and large particle leaching is combined, the result may be a FF release pattern similar to the total line in Figure The small particles likely provide high surface area and may readily leach during the first few PVF of the CLT (FF release, small line in Figure 6.33). Kinetic limitations of the large particles may delay the release of trace elements and contribute to leaching later in the CLT (D release, large line in Figure 6.33). Thus, removal of readily leachable materials through washing may result in a D release pattern similar to that shown in Figure Aqueous Chemistry Indicators Leachates from all slags ranged in ph from approximately 7.8 to 10.4 when the slags were washed prior to placement in the columns. The average difference between minimum and maximum ph in a column is 1.3. A summary of ph, EC, and Eh measurements is shown in Table 6.3. When comparing the washed CLTs to the unwashed slag CLTs, the differences between minimum ph measurements were on average 0.33 (range: to 0.80), the differences between maximum ph measurements were on average (range: to 0.86), and the differences between SS ph measurements were on average 0.83 (range: 0.48 to 1.40). The ph of all slag leachates at the beginning of the washed CLTs were approximately 9.0 and a D trend was observed for all slags. Typical ph release patterns

63 62 observed in the washed CLTs are shown in Figure However, a decrease in ph within the first 5 PVF was observed for the ARC slag before the D trend was observed for the remainder of the test. The MAN slag ph release pattern changed from FF in the continuous-flow CLT to D in the washed CLT, and the WAB ph release pattern changed from SS to D. The ph release pattern change for the MAN slag is likely due to the removal of readily soluble or high surface area material during washing of the slags. In the washed CLTs, the EC ranged from 17 to 197 µs/cm for the ARC, MAN, and WAB slags and from 43 to 783 µs/cm for the SHN slag. When comparing the washed CLTs to the unwashed slag CLTs, the differences between minimum EC measurements were on average µs/cm (range: -126 to 5.0 µs/cm), the differences between maximum EC measurements were on average -593 µs/cm (range: -1,810 to 112 µs/cm), and the differences between SS EC measurements were on average µs/cm (range: -125 to 6.3 µs/cm). The overall reduction in EC surely results from the removal of readily soluble trace elements during washing. The EC in leachates from all slags had a FF trend. Typical EC release patterns observed in the washed CLTs are shown in Figure The FF pattern likely is from readily soluble trace elements on the surface of the slag particles washing away with the first few PVF. No changes in EC release patterns were observed between the continuousflow CLTs and the washed CLTs. The Eh ranged from -102 to 31 mv in the washed CLTs. When comparing the washed CLTs to the continuous-flow CLTs, the differences between minimum Eh measurements were on average mv (range: -171 to 88.0 mv), the differences between maximum Eh measurements were on average 53.3 mv (range: -118 to 15.5 mv), and the differences between SS Eh measurements were on average mv (range: -157 to 37.3 mv).

64 63 The Eh of the ARC and SHN slags trended from reducing to more reducing. The MAN and WAB slags trended from neutral to oxidizing for the fist 2 PVF and then trended to reducing. Typical Eh release patterns observed in the washed CLTs are shown in Figure The Eh release pattern for the SHN slag changed from SS oxidizing to FF reducing. The Eh release pattern for the WAB slag changed from D reducing to FF oxidizing to reducing Peak Concentrations Peak concentrations from the CLTs on the washed slags are compared to peak concentrations from the continuous-flow CLTs in Figure 6.37 and in Table Concentrations below DLs were not graphed in Figure A summary of the peak concentrations is in Table 6.9. In Table 6.26, higher concentration is labeled with washed for the washed CLTs, fast for the continuous-flow CLTs, and same if the concentrations are approximately equal or are both below the LOQ. Points below the 1:1 line in Figure 6.37 correspond to peak concentrations from the washed slags that are lower than peak concentrations from unwashed slags. Peak concentrations for the washed CLTs were lower than those from the continuous-flow CLTs in 41% of the cases and approximately the same for 54% of the cases. The geometric mean of washed CLT concentrations divided by continuous-flow CLT concentrations was 0.5 (1:2 line in Figure 6.37), indicating that on average peak concentrations were less for the washed slag than the unwashed slag. Consistent reductions in peak concentrations were only obtained for cases where the peak concentration for unwashed slag was at least 20 µg/l. When peak concentrations were below 20 µg/l, the peak concentrations from the washed and unwashed slags were comparable.

65 64 The reductions in peak concentrations that were greater than 20 µg/l in the continuous-flow CLTs are likely from the removal of small, high surface area particles, during washing. Washing may also have reduced the quantities of trace elements readily available on the surface of large particles. During the 3 day drying time before the washed slags were placed in columns, surface reactions with the atmosphere may have produced oxides or other compounds that are less soluble, thereby preventing trace elements inside the larger particles from leaching. Washing resulted in a decrease in peak concentrations of Al, As, Ba, Cr, Cu, Mn, Ni, Se, and Tl for all slags. Washing also reduced peak concentrations of Fe for three of the slags (the exception is SHN slag). Peak concentrations of Ag, Be, Cd, Pb, and Sb were below the LOQ or approximately equal to peak concentrations for all of the unwashed slags. Peak concentrations of Zn (ARC and SHN slags) and Fe (SHN slag) for washed slag were approximately equal to peak concentrations for unwashed slag. In three cases, peak concentrations increased modestly after washing (Fe for SHN slag and Zn for the ARC and SHN slags) Cumulative Concentrations Cumulative concentrations from the washed CLTs are compared to cumulative concentrations from the continuous-flow CLTs in Figure A summary of the cumulative concentrations is in Table Points falling below the 1:1 line represent a decrease in cumulative concentration due to use of washed slag instead of unwashed slag in the CLTs. Washing slag does not reduce the cumulative concentration leached for cumulative concentrations below 10 µg/l. For trace elements with cumulative concentrations above 10 µg/l, washing the slags reduces the cumulative concentration.

66 65 Washing reduced the cumulative concentration for 39% of the trace elements. In particular, cumulative concentrations decreased for 6 of 16 trace elements for ARC slag, 6 of 12 trace elements for MAN slag, 3 of 12 trace elements for SHN slag, and 7 of 16 trace elements for WAB slag. Washing reduced concentrations of Al, Ba, Fe, Mn, and Se for all slags or 3 of 4 slags. For all slags, washing resulted in cumulative concentrations of Ag, As, Cd, Cr, Cu, Pb, Sb, and Zn that were higher than cumulative concentrations for at least 3 of 4 of the unwashed slags Comparison to Regulatory Standards Peak concentrations from the washed CLTs are compared to the ESs in NR 140 and the concentration criteria in NR 538 in Table Six trace elements exceed the ESs for the washed CLTs, compared to 10 trace elements for the continuous-flow CLTs. Fewer occurrences of peak concentrations of As, Fe, Mn, Se, and Tl exceeding the ESs were observed for the washed slags. However, peak concentrations of Sb exceeded the ESs for the ARC and WAB washed slags, whereas Sb did not exceed the ES when these slags were tested without washing. Peak concentrations exceeding NR 538 criteria for the washed CLTs were compared to the peak concentrations exceeding NR 538 criteria for the continuous-flow CLTs. Washing the slags did not decrease the number of peak concentrations exceeding Category 1 criteria, but did decrease the frequency of peak concentrations exceeding Category 2 & 3 criteria. The number of peak concentrations exceeding Category 1 was 18 for both washed and unwashed slags. The specific trace elements with peak concentrations exceeding Category 1 varied. Fewer occurrences of Be, Fe, and Tl were observed for the washed slags. However, more occurrences of As, Pb, and Sb exceeding Category 1 were observed for the washed slags. The number of peak concentrations exceeding

67 66 Category 2 & 3 dropped from 5 with unwashed slags to 1 with washed slags. Peak concentrations of Mn, Se, and Tl were reduced below Category 2 & 3 levels, except for Tl for the WAB slag, which was the only peak concentration from the washed slags to exceed Category 2 & 3 criteria. Cumulative concentrations from the washed CLTs compared to the concentration criteria in NR 538 are in Table Cumulative concentrations exceeding NR 538 criteria for the washed CLTs and continuous-flow CLTs have been compared. Washing the slags did not decrease the number of cumulative concentrations exceeding Category 1, but did eliminate all occurrences of cumulative concentrations exceeding Category 2 & 3. The quantity of cumulative concentrations exceeding Category 1 doubled from 7 for unwashed slags to 14 for washed slags. Cumulative concentrations of Al, As, and Mn were reduced, but Cd, Pb, and Sb generally increased. The cumulative concentration of Mn for ARC slag was the only concentration to exceed Category 2 & 3 for the unwashed slags. Washing the ARC slag reduced the cumulative concentration leached to below the Category 2 & 3 criterion. Cumulative concentrations from the washed CLTs were also compared to the ESs and are shown in Table For the MAN and SHN slags, washing the slags did not affect whether cumulative concentrations exceeded the ESs. The cumulative concentration of Mn for the ARC slag exceeded the ESs in the slow CLTs and the continuous-flow CLTs. The cumulative concentration of Tl for the WAB slag exceeded the ES for the washed CLTs, but did not exceed the ES for the continuous-flow CLTs. The cumulative concentration of Tl for the ARC slag did not exceed the ES for the washed CLTs, but did exceed the ES for the continuous-flow CLTs.

68 7. SUMMARY AND CONCLUSIONS 67 The purpose of this study was to assess leaching of trace elements from gray iron slags in the context of their use in sustainable construction applications. Total elemental analyses (TEA), water leach tests (WLTs), and column leach tests (CLTs) were conducted on four slags. The CLTs were conducted using continuous flow or with periodic flow with air or CO 2 introduced into the pore space between flow periods. Leachates from each slag were analyzed for 16 trace elements (Ag, Al, As, Ba, Be, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, Tl, and Zn). Results of the WLTs and TEAs were used to evaluate the suitability of the slags for reuse in terms of Chapter NR 538 of the Wisconsin Administrative Code. Based on the WLT data alone, two of the slags can be used without restriction (including below the water table) and the other two slags can be used in confined and unconfined applications at the ground surface or in the vadose zone (not below the water table). The more restrictive conditions for the two slags were due to higher concentrations of Fe and Mn. When the TEAs were considered, three slags were found to be suitable only for applications at the ground surface or in the vadose zone, and one slag was restricted to subsurface applications in the vadose zone. Trace element concentrations in the leachate from the WLTs were also compared to the Enforcement Standards (ESs) from Chapter NR 140 of the Wisconsin Administrative Code. WLT concentrations exceeded ESs for Fe (WAB slag) and Mn (ARC slag). First flush (FF), delayed (D), and steady-state (SS) leaching patterns were observed for the continuous-flow CLTs. No trace element leached in the same pattern for all four slags, and all three release patterns were observed for each slag and for every test. Of the release patterns observed, 44% were no detection (ND), 19% were FF, 14% were SS, 10% were D, and 13% were a combination release pattern (FF->D) or involved cycling (i.e. FF (C,D)). The ND and D release patterns were more common under continuous water flow

69 68 with no periodic introduction of gases. SS release patterns were about three times more common in the CLTs with periodic air circulation and on washed slags. FF release patterns were more than two times more common in CLTs with continuous flow than in other CLTs. Cyclic release patterns only occurred when gases were periodically introduced, and were observed for 12.5% of the trace elements in the air CLTs and 57.8% of the trace elements in the CO 2 CLTs. Preliminary tests were conducted to assess reproducibility and the effects of seepage velocity on leaching. Three replicate continuous-flow CLTs were conducting using the ARC and WAB slags to assess reproducibility. No differences in release patterns were observed in the repeatability tests on ARC slag and six differences in release patterns were observed for the WAB slag, showing that different specimens may leach differently. Peak concentrations in replicate tests on average differed by a factor of 1.8:1 (geometric mean), and differed by as much as a factor of 16:1. Cumulative concentrations between replicate tests on average varied by a factor of 1.5:1 (geometric mean), and by as much as a factor of 11:1. The reproducibility of the CLTs when using peak concentrations or cumulative concentrations is similar, showing that the average concentration leached throughout the CLTs varies similarly to the peak concentrations leached. When variation in magnitude was considered, the peak concentrations varied by a factor of 1.02:1. This demonstrates that the variations between maximum concentration and the average concentration, and minimum concentration and the average concentration are nearly the same. Varying the seepage velocity had no consistent effect on the leaching patterns or the concentrations of trace elements in the leachates. Peak concentrations from the continuous-flow CLTs were on average 30 times greater than WLT concentrations. Similarly, cumulative concentrations (i.e., flow-weighted average concentrations) were on average 4.3 times greater than the WLT concentrations.

70 69 Moreover, cumulative concentrations of Al, As, and Se were always greater than the corresponding WLT concentrations, possibly due to greater contact time in the CLTs, which allowed for increased dissolution. Periodically introducing air into the columns caused peak concentrations to decrease and cumulative concentrations to increase. A cycling effect was also observed in the release pattern in each subsequent period of continuous water flow after air was introduced. The majority of the peak concentrations did not vary much between the air and continuousflow CLTs. Cumulative concentrations from the air CLTs increased for the majority of the trace elements when compared to the continuous-flow CLTs. This shows that the introduction of air did not have a large effect on peak concentrations, but did increase the leaching potential of the slags. Periodically introducing CO 2 caused both peak and cumulative concentrations to increase, induced a cycling effect in the leaching pattern similar to that caused by introduction of air, and caused the ph of the leachate to drop by 2.7, on average. The majority of the trace elements with peak concentrations above DLs had higher peak concentrations in the CO 2 CLTs compared to the continuous-flow CLTs. The majority of the cumulative concentrations for the CO 2 CLTs were greater than the cumulative concentrations for the continuous-flow CLTs. The increases in concentrations most likely result from increased solubility of most trace elements at the reduced ph range observed in the CO 2 CLTs. Peak and cumulative concentrations from the CLTs were compared to groundwater enforcement standards (ESs) in Chapter NR 140 of the Wisconsin Administrative Code. One peak and cumulative concentration for at least one trace element from each CLT (i.e., air CLTs), but not necessarily every slag for each CLT, exceeded the ESs. Often, more than one trace element had peak or cumulative concentrations greater than the ESs. The CO 2

71 70 CLTs had the highest (peak concentrations in excess of 20,000 µg/l for Fe and Mn) peak and cumulative concentrations observed. The trace elements with the highest leached concentrations were Al, Fe, and Mn. Se and Tl were commonly leached at concentrations greater than the ESs. Trace elements leached at concentrations greater than the ESs include Fe, Mn, Pb, Sb, Se, and Tl. Tests were conducted to determine if washing the slags would reduce peak concentrations, and result in fewer peak concentrations exceeding the ESs. Washing had no effect on peak and cumulative concentrations of trace elements when the peak concentration for unwashed slag was below 20 µg/l and the cumulative concentration for unwashed slag was below 10 µg/l. For trace elements with unwashed slag peak concentrations above 20 µg/l and cumulative concentrations above 10 µg/l, washing reduced peak concentrations by up to a factor of 110 and cumulative concentrations by up to a factor of 75. Washing slags likely reduced leachate concentrations by removing small, high surface area particles from the slag, thereby reducing the quantity of readily leachable trace elements.

72 8. REFERENCES 71 ASTM D , Standard Specification for Reagent Water, ASTM International. ASTM D Standard Test Method for Shake Extraction of Solid Waste with Water, ASTM International. Apul, D. S., Fallman, A. M., and Comans, R. N. J. (2005). Simultaneous Application of Dissolution/Precipitation and Surface Complexation/Surface Precipitation Modeling to Contaminant Leaching. Environmental Science & Technology, 39, Beneficial Use of Industrial Byproducts. Wisconsin Administrative Code, NR 538. Beneficial Use of Industrial Byproducts: 2000 Usage Summary. Wisconsin Department of Natural Resources (WDNR) Bureau of Waste Management, Benjamin, M. M. (2002). Water Chemistry. New York, McGraw-Hill Companies, Inc. Berthrouex, P. M. and Brown, L. C., (1994). Statistics for Environmental Engineering. Boca Raton, CRC Press, Inc. Creek, D. N., and Shackelford, C.D. (1992). Permeability and Leaching Characteristics of Fly Ash Liner Materials. Transportation Research Record, 1345, Deng, A. and Tikalsky, P. (2006). Metallic Characterization of Foundry By-Products per Waste Streams and Leaching Protocols. Journal of Environmental Engineering, 132(6), Groundwater Quality. Wisconsin Administrative Code, NR 140. Lee, A. R. (1974). Blastfurnace and Steel Slag: Production, properties, and uses. New York, John Wiley & Sons, Inc. Lewis, D. W. (1992). Properties and Uses of Iron and Steel Slags. National Slag Association Presented as Symposium on Slag National Institute for Transport and Road Research South Africa. Liu, C. F. and Shih, S. M. (2004). Iron Blast Furnace Slag/Hydrated Lime Sorbents for Flue Gas Desulfurization. Environmental Science & Technology, 38, Mayes, W. M., Younger, P. L., and Aumonier, J. (2006). Buffering of Alkaline Steel Slag Leachate across a Natural Wetland. Environmental Science & Technology, 40, Proctor D.M., Fehling K.A., Shay E.C., Wittenborn J.L, Green J.J., Avent C., Bigham R.D., Connolly M., Lee B., Shepker T.O., Zak M.A. (2000). "Physical and Chemical Characteristics of Blast Furncae, Basic Oxygen Furnace, and Electric Arc Furnace Steel industry Slags." Environmental Science and Technology 34(8):

73 72 Roadcap, G. S., Kelly, W. R., and Bethke, C. M. (2005). Geochemistry of Extremely Alkaline (ph > 12) Ground Water in Slag-Fill Aquifers. Ground Water, Vol. 43, No. 6, Sanchez, F., Garrabrants, A. C., and Kosson, D. S. (2003). Effects of Intermittent Wetting on Concentration Profiles and Release from a Cement-Based Waste Matrix. Environmental Engineering Science, 20(2), Stumm, W. (1992). Chemistry of the Solid-Water Interface. New York, John Wiley & Sons, Inc. Stumm W. and Morgan J. J. (1996). Aquatic Chemistry. New York, John Wiley & Sons, Inc. Takeno, N. (2005). Atlas of Eh-pH Diagrams. Geological Survey of Japan Open File Report No.419. United States Environmental Protection Agency (2005). List of Drinking Water Contaminants and MCLs. United States Environmental Protection Agency. (1992). Acid Digestion of Aqueous Samples for Metals, Method 3010A. SW-846, Ch United States Environmental Protection Agency. (1994). Metals by Inductively Coupled Plasma Mass Spectrometry, Method SW-846, Ch United States Environmental Protection Agency. (1994). Determination of Inorganic Anions by Ion Chromatography, Method SW-846, Ch 5. United States Environmental Protection Agency. (1994). Determination of Metals and Trace Elements in Water and Wastes by Inductively Coupled Plasma-Atomic Emission Spectrometry, Method van Ravenswaay, E. O. (2000). Iron and Steel Industry. Michigan State University. Younger, P. L., Banwart, S. A., and Hedin, R. S. (2002). Mine Water. Dordrecht, Kluwer Academic publishers.

74 TABLES 73

75 74 Table 3.1. Material d 10 (mm) Material properties of the 5 slags and the natural sand. d 30 (mm) d 60 (mm) C u C z USCS Classification Specific Gravity Average K (m/s) Percent Iron ARC SW x MAN SW x MTG SP x SHN SW x WAB SW x SAND SP Notes: Hyphen (-) indicates measurement was not made. d 10 = diameter corresponding to 10% finer d 30 = diameter corresponding to 30% finer d 60 = diameter corresponding to 60% finer C u = uniformity coefficient C z = coefficient of gradation K = hydraulic conductivity

76 75 Table 3.2. Chapter NR 538 TEA criteria and results. Concentrations exceeding Category 1 are in BOLD and concentrations exceeding Category 2 are indicated with an asterisk (*). NR 538 TEA Slag Element Cat. 1 Cat. 2 ARC MAN MTG SHN WAB (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) Ag Al As Ba 1, Be * Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn Notes: An asterisk (*) indicates the concentration exceeds Category 2 concentration. Hyphen (-) indicates data was not collected.

77 76 Table 3.3. Major chemical components of the 5 slags in this study. Chemical Percent of Composition Species ARC MAN MTG SHN WAB SiO Al 2 O Fe 2 O CaO MgO MnO Trace MeO Notes: Trace MeO is the sum of trace metal oxides in the slag.

78 77 Table 4.1. Element Summaries of detection limits (DL) and limits of quantitation (LOQ) for WLTs and CLTs. Repeatability and Air, CO Continuous Flow 2, and WLTs Slow Flow Rate Washed Slag CLT CLTs CLTs DL (µg/l) LOQ (µg/l) DL (µg/l) LOQ (µg/l) DL (µg/l) LOQ (µg/l) DL (µg/l) LOQ (µg/l) Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb a Sb Se Tl b Zn Notes: a DL for SHN and MTG slags b DL for SHN slag Hyphen (-) indicates data was not collected.

79 78 Table 5.1. Concentrations of trace elements in WLT leachates compared to NR 140 ESs. Concentrations exceeding NR 140 ESs are shown in BOLD. Element Concentration (µg/l) ARC MAN MTG SHN WAB WI ESs MCLs Ag Al As Ba ,000 2,000 Be < < < < < Cd < < Cr < Cu ,300 1,300 Fe < 2 < 2 < 2 < a - Mn a - Ni Pb Sb < 0.22 < 0.22 < < Se < Tl < < < < Zn ,000 a - Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. indicates water quality standards that are not based on health risk.

80 79 Table 5.2. Beneficial reuse categories and reuse applications from NR 538. Industrial Byproduct Category (1) Raw Material for Manufacturing a Product X X X X X (2) Waste Stabilization / Solidification X X X X X (3) Supplemental Fuel Source / Energy Recovery X X X X X (4) Landfill Daily Cover / Internal Structures X X X X X (5) Confined Geotechnical Fill (a) commercial, industrial or institutional building subbase (b) paved lot base, subbase & subgrade fill (c) paved roadway base, subbase & subgrade fill (d) utility trench backfill (e) bridge abutment backfill (f) tank, vault or tunnel abandonment (g) slabjacking material X X X X (6) Encapsulated Transportation Facility Embankment X X X X (7) Capped Transportation Facility Embankment X X X (8) Unconfined Geotechnical Fill X X X (9) Unbonded Surface Course X X (10) Bonded Surface Course X X (11) Decorative Stone X X (12) Cold Weather Road Abrasive X X Note: General beneficial use in accordance with s. NR (3) Notes: Refer to s. NR for description of each beneficial use X

81 80 Table 5.3. Concentrations of trace elements in WLT leachates compared to NR 538 Category 1. Concentrations exceeding NR 538 Category 1 are shown in BOLD. Element Concentration (µg/l) ARC MAN MTG SHN WAB Category 1 Ag Al ,500 As Ba Be < < < < < Cd < < Cr < Cu Fe < 2 < 2 < 2 < Mn Ni Pb Sb < 0.22 < 0.22 < < Se < Tl < < < < Zn ,500 Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

82 81 Table 6.1. Summary of release patterns for the CLTs (Ag to Cu). Release patterns in BOLD indicate a significant change from the release pattern for the continuous-flow CLTs. Slag Test Type Ag Al As Ba Be Cd Cr Cu Continuous 1 ND D ND - ND ND FF - Continuous 2 ND D ND FF ND ND FF ND Continuous 3 ND D ND FF ND ND FF ND ARC Washed ND D ND FF ND ND FF ND Air Circulation ND D SS FF (C,D) ND ND ND SS CO 2 Circulation SS D->ND SS FF (C,FF) ND SS (C,FF) SS ND Slow Flow ND FF->D SS SS ND ND ND SS Continuous ND FF SS - ND ND ND - Washed ND D ND D ND ND ND ND MAN Air Circulation ND D (C,FF) SS SS ND ND ND SS CO 2 Circulation SS D->ND SS D (C,FF) ND D (C,FF) SS ND Slow Flow ND D SS D ND ND ND SS MTG Continuous FF D FF - ND FF FF - SAND Continuous ND FF ND - ND ND ND - Continuous ND D ND - ND ND ND - Washed ND D SS D ND ND ND FF SHN Air Circulation ND D (C,FF) SS D (C,FF) ND ND ND SS CO 2 Circulation SS (C,D) D->ND SS (C,D) D (C,FF) ND ND SS (C,D) ND Slow Flow ND D ND D ND ND ND SS Continuous 1 ND D ND - ND ND ND - Continuous 2 ND D ND FF ND ND ND ND Continuous 3 ND D ND FF ND ND ND ND WAB Washed ND D SS FF->D ND ND ND ND Air Circulation ND D (C,FF&D) SS FF ND ND ND SS CO 2 Circulation SS (C,FF) D->ND SS (C,FF) D (C, FF) ND SS (C,FF) SS ND Slow Flow ND D ND D ND ND ND SS Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. (C, FF) = Cycling occurring in a FF pattern within each period of continuous water flow.

83 Table 6.1. Summary of release patterns for the CLTs (Fe to Zn). Release patterns in BOLD indicate a significant change from the release pattern for the continuous-flow CLTs. Slag Test Type Fe Mn Ni Pb Sb Se Tl Zn Continuous 1 FF->D FF - ND - FF FF FF Continuous 2 FF->D FF FF ND ND FF FF FF Continuous 3 FF->D FF FF ND ND FF FF FF ARC Washed D FF FF ND ND FF FF FF Air Circulation FF->D FF FF ND ND D FF FF CO 2 Circulation SS (C,FF) FF (C,FF) SS (C,FF) ND D FF FF (C,FF) FF (C) Slow Flow FF->D D ND SS ND ND ND SS Continuous D D - ND - SS ND D Washed D D ND ND ND ND ND FF MAN Air Circulation D D ND SS ND SS SS FF CO 2 Circulation D (C,FF) FF (C,FF) D (C,FF) ND ND ND D SS (C,FF) Slow Flow ND FF SS SS ND SS ND D MTG Continuous FF FF - FF - FF FF FF SAND Continuous FF FF - SS - FF ND FF Continuous D FF - ND - FF ND ND Washed SS FF ND ND ND FF ND FF SHN Air Circulation D FF ND SS SS SS SS FF CO 2 Circulation D (C,FF) D (C,FF) D (C,FF) FF SS (C,D) FF FF (C) FF (C) Slow Flow ND FF ND SS ND SS SS SS Continuous 1 D FF - SS - SS ND D Continuous 2 SS FF->D ND ND ND ND ND FF Continuous 3 D FF->D ND ND ND ND ND SS WAB Washed SS FF->D ND ND ND ND ND SS Air Circulation D (C,FF) FF (C,FF) ND ND ND D (C,FF) SS SS CO 2 Circulation D (C, FF) FF (C,FF) SS (C,FF) D (C, FF) ND ND FF (C,FF) FF (C,FF) Slow Flow ND FF ND SS ND SS SS SS Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. (C, FF) = Cycling occurring in a FF pattern within each period of continuous water flow. 82

84 83 Table 6.2. Release patterns from the continuous-flow CLTs. Slag Test Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn f-1 ND D ND - ND ND FF - FF->D FF - ND - FF FF FF ARC f-2 ND D ND FF ND ND FF ND FF->D FF FF ND ND FF FF FF f-3 ND D ND FF ND ND FF ND FF->D FF FF ND ND FF FF FF MAN f-1 ND FF SS - ND ND ND - D D - ND - SS ND D MTG f-1 FF D FF - ND FF FF - FF FF - FF - FF FF FF SHN f-1 ND D ND - ND ND ND - D FF - ND - FF ND ND f-1 ND D ND - ND ND ND - D FF - SS - SS ND D WAB f-2 ND D ND FF ND ND ND ND SS FF->D ND ND ND ND ND FF f-3 ND D ND FF ND ND ND ND D FF->D ND ND ND ND ND SS SAND f-1 ND FF ND - ND ND ND - FF FF - SS - FF ND FF Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

85 84 Table 6.3. Summary of minimum (min), maximum (max), and steady-state (SS) aqueous chemistry indicators (ph, EC, Eh) for the CLTs. Continuous-Flow CLTs Slag Test Type ph EC (µs/cm) Eh (mv) Min Max SS Min Max SS Min Max SS Continuous ARC Continuous Continuous Continuous Ave MAN Continuous MTG Continuous , SAND Continuous SHN Continuous , Continuous WAB Continuous Continuous Continuous Ave Slag Test Type Continuous-Flow CLTs (without first 3 PVF) ph EC (µs/cm) Eh (mv) Min Max SS Min Max SS Min Max SS Continuous ARC Continuous Continuous Continuous Ave MAN Continuous MTG Continuous SAND Continuous SHN Continuous Continuous WAB Continuous Continuous Continuous Ave Slow Flow CLTs Slag ph EC (µs/cm) Eh (mv) Min Max SS Min Max SS Min Max SS ARC None MAN None MTG , SAND SHN , WAB Notes: None means no steady-state pattern was observed at the end of the CLT

86 85 Table 6.3. Summary of minimum (min), maximum (max), and steady-state (SS) aqueous chemistry indicators (ph, EC, Eh) for the CLTs. Air CLTs Slag ph EC (µs/cm) Eh (mv) Min Max SS Min Max SS Min Max SS ARC MAN SHN , WAB Air CLTs (without cycle before air introduction, first 3 PVF) Slag ph EC (µs/cm) Eh (mv) Min Max SS Min Max SS Min Max SS ARC MAN SHN WAB CO 2 CLTs Slag ph EC (µs/cm) Eh (mv) Min Max SS Min Max SS Min Max SS ARC None MAN None SHN ,640 None WAB None CO 2 CLTs (without cycle before CO 2 introduction, first 3 PVF) Slag ph EC (µs/cm) Eh (mv) Min Max SS Min Max SS Min Max SS ARC None MAN None SHN ,100 None WAB None Washed CLTs Slag ph EC (µs/cm) Eh (mv) Min Max SS Min Max SS Min Max SS ARC MAN SHN WAB Notes: None means no steady-state pattern was observed at the end of the CLT

87 86 Table 6.4. Peak CLT concentrations (µg/l) from the continuous-flow CLTs. Concentrations exceeding Enforcement Standards concentration criteria are shown in BOLD. Peak Concentration (µg/l) Slag Test Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn f-1 < < < 1.5 < ,020 - < ARC f-2 < < < 0.2 < < 1.9 1,460 14, < 3.0 < f-3 < < < 0.2 < < , < 3.0 < Ave < < < 1.5 < < , < 4.3 < MAN f-1 < < 1.1 < < < MTG f < , SHN f-1 < < < 1.5 < 1.1 < < f-1 < < < 1.5 < WAB f-2 < 2.1 1,080 < < 0.2 < 0.6 < < 1.2 < 3.0 < 2.1 < 3.6 < f-3 < < < 0.2 < 0.6 < 1.0 ND < < 3.6 < Ave < < < 1.5 < SAND f-1 < < < < WI NR 140 ESs , , a 50 a ,000 a Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

88 87 Table 6.5. Cumulative concentrations (µg/l) from the continuous-flow CLTs. Concentrations exceeding NR 140 concentration criteria are shown in BOLD. Cumulative Concentration (µg/l) Slag Test Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn f ARC f , f , Ave MAN f MTG f , SHN f , f WAB f f Ave SAND f WI NR 140 ESs , , a 50 a ,000 a Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

89 88 Table 6.6. Peak CLT concentrations (µg/l) from the continuous-flow tests compared to WLT concentration criteria from NR 538. Concentrations exceeding Category 1 WLT concentration criteria are in BOLD and concentrations exceeding Category 2 & 3 WLT concentration criteria are indicated with an asterisk (*). Peak Concentration (µg/l) Slag Test Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn f-1 < < < 1.5 < ,020* - < * 185 ARC f-2 < < < 0.2 < < 1.9 1,460 14,400* 3.75 < 3.0 < * 9.61 f-3 < < < 0.2 < < ,900* 4.26 < 3.0 < * 21.8* 12.6 MAN f-1 < < 1.1 < < < MTG f , < ,000* * - 215* 734* 297 SHN f-1 < 1.9 2,050 < < 1.5 < 1.1 < < f-1 < < < 1.5 < * * 160 WAB f-2 < 2.1 1,080 < < 0.2 < 0.6 < < 1.2 < 3.0 < 2.1 < 3.6 < f-3 < < < 0.2 < 0.6 < 1.0 < * 50.3 < < 3.6 < SAND f-1 < < < < * * 84 NR 538 Cat 1-1, ,500 NR 538 Cat 2 & 3-15, , ,300 1, ,000 Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

90 89 Table 6.7. Cumulative concentrations (µg/l) from the continuous-flow CLTs compared to NR 538 WLT concentration criteria. Concentrations exceeding NR 538 Category 1 WLT concentration criteria are shown in BOLD and concentrations exceeding Category 2 & 3 WLT concentration criteria are indicated with an asterisk (*). Cumulative Concentration (µg/l) Slag Test Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn f * ARC f ,260* f ,150* Ave * MAN f MTG f ,920* * 12.7 SHN f , f WAB f f Ave SAND f NR 538 Cat 1-1, ,500 NR 538 Cat 2 & 3-15, , ,300 1, ,000 Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

91 90 Table 6.8. Release patterns for the slow CLTs. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC ND D ND FF ND ND FF ND D FF FF ND ND FF FF FF MAN ND D ND D ND ND ND ND D D ND ND ND ND ND FF SHN ND D SS D ND ND ND FF SS FF ND ND ND FF ND FF WAB ND D SS FF->D ND ND ND ND SS FF->D ND ND ND ND ND SS Notes: FF: first flush, D: delayed, SS: steady-state, ND: no detection, and X->XX: release pattern X changing to release pattern XX.

92 91 Table 6.9. Summary of peak concentrations (µg/l) for the CLTs (Ag to Cu). Slag Test Type Ag Al As Ba Be Cd Cr Cu Continuous 1 < < < 1.5 < Continuous 2 < < < 0.2 < < 1.9 Continuous 3 < < < 0.2 < < 1.9 ARC Continuous Ave < < < 1.5 < < 1.9 Washed < < 0.2 < < 1.9 Air Circulation < 1.0 < 1.3 < CO 2 Circulation < Slow Flow < < 1.0 < 1.3 < Continuous < < 1.1 < Washed < < < 0.2 < 0.6 < 1.0 < 1.9 MAN Air Circulation < 1.0 < 1.3 < CO 2 Circulation < Slow Flow < < 1.0 < 1.3 < MTG Continuous , < SAND Continuous < < < < Continuous < 1.9 2,050 < < 1.5 < 1.1 < Washed , < 0.2 < 0.6 < SHN Air Circulation < 3.2 2, < 1.0 < 1.3 < CO 2 Circulation , < 1.0 < Slow Flow , < 1.0 < 1.3 < Continuous 1 < < < 1.5 < Continuous 2 < 2.1 1,080 < < 0.2 < 0.6 < Continuous 3 < < < 0.2 < 0.6 < 1.0 < 1.9 WAB Continuous Ave < < < 1.5 < Washed < < 0.2 < 0.6 < 1.0 < 1.9 Air Circulation < < 1.0 < 1.3 < CO 2 Circulation < Slow Flow < 1.0 < 1.3 < Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

93 92 Table 6.9. Summary of peak concentrations (µg/l) for the CLTs (Fe to Zn). Slag Test Type Fe Mn Ni Pb Sb Se Tl Zn Continuous ,020 - < 4.3 < Continuous 2 1,460 14, < 3.0 < Continuous , < 3.0 < ARC Continuous Ave , < 4.3 < Washed , < 3.0 < Air Circulation 1,370 3, < CO 2 Circulation 183,000 > 20, < Slow Flow < < 8.3 < Continuous < < Washed < 1.2 < 3.0 < 2.1 < 3.6 < MAN Air Circulation < < CO 2 Circulation 245,000 > 20, < Slow Flow < < MTG Continuous , SAND Continuous Continuous < Washed < 1.2 < 3.0 < < SHN Air Circulation CO 2 Circulation 15,500 13, Slow Flow < < < Continuous Continuous < 1.2 < 3.0 < 2.1 < 3.6 < Continuous < < 3.6 < WAB Continuous Ave Washed < 3.0 < 2.1 < 3.6 < Air Circulation < < CO 2 Circulation 206,000 > 20, < Slow Flow < Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

94 93 Table Summary of cumulative concentrations (µg/l) for the CLTs (Ag to Cu). Slag Test Type Ag Al As Ba Be Cd Cr Cu Continuous Continuous Continuous ARC Continuous Ave Washed Air Circulation CO 2 Circulation Slow Flow Continuous Washed MAN Air Circulation CO 2 Circulation Slow Flow MTG Continuous SAND Continuous Continuous , Washed , SHN Air Circulation , CO 2 Circulation Slow Flow Continuous Continuous Continuous WAB Continuous Ave Washed Air Circulation CO 2 Circulation Slow Flow Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

95 94 Table Summary of cumulative concentrations (µg/l) for the CLTs (Fe to Zn). Slag Test Type Fe Mn Ni Pb Sb Se Tl Zn Continuous Continuous , Continuous , ARC Continuous Ave , Washed Air Circulation , CO 2 Circulation 61,900 7, Slow Flow Continuous Washed MAN Air Circulation CO 2 Circulation 52,100 5, Slow Flow MTG Continuous , SAND Continuous Continuous Washed SHN Air Circulation CO 2 Circulation Slow Flow Continuous Continuous Continuous WAB Continuous Ave Washed Air Circulation CO 2 Circulation 36,300 6, Slow Flow Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

96 95 Table Peak concentrations from the slow CLTs compared to peak concentrations from the continuous-flow CLTs. The higher concentration between the two tests is labeled with slow for the slow CLTs, fast for the continuous-flow CLTs, and same for concentrations that are approximately equal or concentrations from both tests are below the LOQ. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC Same Slow Same Slow Same Same Fast Same Fast Fast Slow Same Same Fast Fast Slow MAN Same Slow Fast - Same Same Same - Fast Fast - Same - Fast Same Slow SHN Same Slow Same - Same Same Same - Fast Fast - Same - Fast Same Slow WAB Same Fast Same Fast Same Same Same Fast Fast Fast Fast Same Same Same Same Fast Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

97 96 Table Peak Concentrations (µg/l) from the slow CLTs compared to NR 140 ESs and NR 538 Criteria. Concentrations above NR 140 ESs are shown in BOLD. Concentrations exceeding Category 1 are shown in BOLD and concentrations exceeding Category 2 & 3 are indicated with an asterisk (*). Peak Concentration (µg/l) Compared to NR 140 ESs Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC < < 0.2 < < , < 3.0 < MAN < < < 0.2 < 0.6 < 1.0 < < 1.2 < 3.0 < 2.1 < 3.6 < SHN , < 0.2 < 0.6 < < 1.2 < 3.0 < < WAB < < 0.2 < 0.6 < 1.0 < < 3.0 < 2.1 < 3.6 < NR 140 ESs , , a 50 a ,000 a Peak Concentration (µg/l) Compared to NR 538 Criteria Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC < < 0.2 < < ,530* 4.40 < 3.0 < * 103 MAN < < < 0.2 < 0.6 < 1.0 < < 1.2 < 3.0 < 2.1 < 3.6 < SHN , < 0.2 < 0.6 < < 1.2 < 3.0 < < WAB < < 0.2 < 0.6 < 1.0 < < 3.0 < 2.1 < 3.6 < Category 1-1, ,500 Category 2 & 3-15, , ,300 1, ,000 Category , Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

98 97 Table Cumulative concentration (µg/l) from the slow CLTs compared to NR 538. Concentrations exceeding Category 1 are shown in BOLD and concentrations exceeding Category 2 & 3 are indicated with an asterisk (*). Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC MAN SHN , WAB Category 1-1, ,500 Category 2 & 3-15, , ,300 1, ,000 Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. Table Cumulative concentrations (µg/l) from the slow CLTs compared to NR 140 ESs. Concentrations exceeding the ESs are shown in BOLD. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC MAN SHN , WAB NR 140 ESs , , a 50 a ,000 a Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

99 98 Table Release patterns observed for the air CLTs. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC ND D SS MAN SHN WAB ND ND ND D (C,FF) D (C,FF) D (C,FF&D) FF (C,D) ND ND ND SS FF->D FF FF ND ND D FF FF SS SS ND ND ND SS D D ND SS ND SS SS FF SS D (C,FF) ND ND ND SS D FF ND SS SS SS SS FF SS FF ND ND ND SS D (C,FF) FF (C,FF) ND ND ND Notes: FF: first flush, D: delayed, SS: steady-state, ND: no detection, X (C, XX): overall release pattern (cycling observed, cycling release pattern), and X->XX: release pattern X changing to release pattern XX. D (C,FF) SS SS Table CLT yielding higher peak concentration for continuous-flow and air CLTs; air indicates the air CLT had a higher concentration, fast indicates that continuous-flow CLT had higher a concentration, and, same indicates that concentrations are approximately equal or concentrations from both CLTs are below the LOQ. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC Same Air Same Air Same Same Fast Same Air Fast Air Same Same Fast Air Fast MAN Same Air Fast - Same Same Same - Air Fast - Same - Air Same Fast SHN Same Air Same - Same Same Same - Fast Fast - Same - Fast Same Fast WAB Same Fast Same Fast Same Same Same Fast Air Fast Fast Same Same Air Same Fast Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

100 99 Table Peak concentrations (µg/l) from the air CLTs compared to NR 140 ESs and NR 538 Criteria. Concentrations above NR 140 ESs are shown in BOLD. Concentrations above NR 538 Category 1 are shown in BOLD and concentrations above Category 2 & 3 are indicated with an asterisk (*). Peak Concentration (µg/l) Compared to NR 140 ESs Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC < 1.0 < 1.3 < ,370 3, < MAN < 1.0 < 1.3 < < < SHN < 3.2 2, < 1.0 < 1.3 < WAB < < 1.0 < 1.3 < < < NR 140 ESs , , a 50 a ,000 a Peak Concentration (µg/l) Compared to NR 538 Criteria Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC < 1.0 < 1.3 < ,370 3,600* 9.75 < * 67.7 MAN < 1.0 < 1.3 < < < * 30.2 SHN < 3.2 2, < 1.0 < 1.3 < * 14.1 WAB < < 1.0 < 1.3 < < < * 12.9 Category 1-1, ,500 Category 2 &3-15, , ,300 1, ,000 Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

101 100 Table Cumulative concentration (µg/l) from the air CLTs compared to concentrations from NR 538. Concentrations exceeding Category 1 are shown in BOLD and concentrations exceeding Category 2 & 3 are indicated with an asterisk (*). Cumulative Concentration (µg/l) Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC ,320* MAN SHN , WAB Category 1-1, ,500 Category 2 &3-15, , ,300 1, ,000 Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. Table Cumulative concentrations (µg/l) from the air CLTs compared to NR 140 ESs. Concentrations exceeding the ESs are shown in BOLD. Cumulative Concentration (µg/l) Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC , MAN SHN , WAB NR 140 ESs , , a 50 a ,000 a Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

102 101 Table Release patterns for the CO 2 CLTs. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC SS D->ND SS MAN SS D->ND SS SHN WAB SS (C,D) SS (C,FF) D->ND D->ND SS (C,D) SS (C,FF) FF (C,FF) D (C,FF) D (C,FF) D (C, FF) ND ND ND ND SS (C,FF) D (C,FF) ND SS (C,FF) SS SS SS (C,D) SS ND ND ND ND SS (C,FF) D (C,FF) D (C,FF) D (C, FF) FF (C,FF) FF (C,FF) D (C,FF) FF (C,FF) SS (C,FF) D (C,FF) D (C,FF) SS (C,FF) ND D FF FF (C,FF) ND ND ND D FF D (C, FF) SS (C,D) ND FF (C) SS (C,FF) FF FF (C) FF (C) Notes: FF: first flush, D: delayed, SS: steady-state, ND: no detection, X (C, XX): overall release pattern (cycling observed, cycling release pattern), and X->XX: release pattern X changing to release pattern XX. ND FF (C,FF) FF (C,FF) Table Peak concentrations from the CO 2 CLTs compared to peak concentrations from the continuous flow CLTs. The higher concentration between the two tests is labeled with CO 2 for the CO 2 CLTs, fast for the continuous flow CLTs, and same for concentrations that are approximately equal or concentrations from both tests are below the LOQ. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC Same Fast Same CO 2 Same Same Fast Same CO 2 CO 2 CO 2 Same Same Fast CO 2 CO 2 MAN Same CO 2 Fast - Same Same Same - CO 2 CO 2 - Same - Fast CO 2 CO 2 SHN Same Fast Same - Same Same Same - CO 2 CO 2 - CO 2 - Fast Same CO 2 WAB Same CO 2 Same CO 2 Same Same Same Fast CO 2 CO 2 CO 2 CO 2 Same Same CO 2 CO 2 Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element

103 102 Table Cumulative concentrations (µg/l) from the CO 2 CLTs compared to NR 538. Concentrations exceeding Category 1 are shown in BOLD, concentrations exceeding Category 2 & 3 are indicated with an asterisk (*), and concentrations exceeding Category 4 are shown with two asterisks (**). Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC ,900** 7,310* MAN ,100** 5,780* SHN * WAB ,300** 6,830* Category 1-1, ,500 Category 2 & 3-15, , ,300 1, ,000 Category , Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

104 103 Table Peak Concentrations (µg/l) from the CO 2 CLTs compared to NR 140 ESs and NR 538 Criteria. Concentrations above NR 140 ESs are shown in BOLD. Concentrations exceeding Category 1 are shown in BOLD, concentrations exceeding Category 2 & 3 are indicated with an asterisk (*), and concentrations exceeding Category 4 are shown with two asterisks (**). Peak Concentration (µg/l) Compared to NR 140 ESs Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC < ,000 >20, < MAN < ,000 >20, < SHN , < 1.0 < ,500 13, WAB < ,000 >20, < NR 140 ESs , , a 50 a ,000 a Peak Concentration (µg/l) Compared to NR 538 Criteria Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC < ,000** >20,000* 21.2 < * * 160 MAN < ,000** >20,000* 220* < * 122 SHN , < 1.0 < ,500** 13,700* * 16.5* * 119 WAB < ,000** >20,000* * 16.7* < * 145 Category 1-1, ,500 Category 2 & 3-15, , ,300 1, ,000 Category , Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

105 104 Table Cumulative concentrations (µg/l) from the CO 2 CLTs compared to NR 140 ESs. Concentrations exceeding the ESs are shown in BOLD. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC ,900 7, MAN ,100 5, SHN WAB ,300 6, NR 140 ESs , , a 50 a ,000 a Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

106 105 Table Release patterns for the washed CLTs. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC ND FF->D SS SS ND ND ND SS FF->D D ND SS ND ND ND SS MAN ND D SS D ND ND ND SS ND FF SS SS ND SS ND D SHN ND D SS D ND ND ND SS D FF ND SS ND D ND SS WAB ND D ND D ND ND ND SS ND FF ND SS ND SS SS SS Notes: FF: first flush, D: delayed, SS: steady-state, ND: no detection, and X->XX: release pattern X changing to release pattern XX. Table CLT yielding higher peak concentration for continuous-flow and washed CLTs; washed indicates the washed CLT had a higher concentration, fast indicates that continuous-flow CLT had higher a concentration, and, same indicates that concentrations are approximately equal or concentrations from both CLTs are below the LOQ. Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC Same Fast Same Fast Same Same Fast Same Fast Fast Same Same Same Fast Fast Washed MAN Same Fast Fast - Same Same Same - Fast Fast - Same - Fast Same Fast SHN Same Fast Same - Same Same Same - Washed Fast - Same - Fast Same Washed WAB Same Fast Same Fast Same Same Same Fast Fast Fast Fast Same Same Same Same Fast Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element.

107 106 Table Peak concentrations (µg/l) from the washed CLTs compared to NR 140 ESs and NR 538 Criteria. Concentrations above NR 140 ESs are shown in BOLD. Concentrations above NR 538 Category 1 are shown in BOLD and concentrations above Category 2 & 3 are indicated with an asterisk (*). Peak Concentration (µg/l) Compared to Nr 140 ESs Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC < < 1.0 < 1.3 < < < 8.3 < MAN < < 1.0 < 1.3 < < < SHN , < 1.0 < 1.3 < < < < WAB < 1.0 < 1.3 < < NR 140 ESs , , a 50 a ,000 a Peak Concentration (µg/l) Compared to NR 538 Criteria Slag Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC < < 1.0 < 1.3 < < < 8.3 < MAN < < 1.0 < 1.3 < < < SHN , < 1.0 < 1.3 < < < < WAB < 1.0 < 1.3 < < * 34.5 Category 1-1, ,500 Category 2 &3-15, , ,300 1, ,000 Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

108 107 Table Cumulative concentration (µg/l) from the washed CLTs compared to concentrations from NR 538. Concentrations exceeding Category 1 are shown in BOLD and concentrations exceeding Category 2 & 3 are indicated with an asterisk (*). Test Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC MAN SHN WAB Category 1-1, ,500 Category - 15, , ,300 1, ,000 2 & 3 * Hyphen (-) indicates measurement was not made or no standard exists for that element. Table Cumulative concentrations (µg/l) from the washed CLTs compared to NR 140 ESs. Concentrations exceeding the ESs are shown in BOLD. Test Ag Al As Ba Be Cd Cr Cu Fe Mn Ni Pb Sb Se Tl Zn ARC MAN SHN WAB NR 140 ESs , , a 50 a ,000 a Notes: Hyphen (-) indicates measurement was not made or no standard exists for that element. a Water quality standards that are not based on health risk.

109 FIGURES 108

110 109 Percent Finer (%) ARC MAN MTG SAND SHN WAB Particle Size (mm) Figure 3.1. Particle size distribution curves for the 5 slags and sand.

111 Figure 4.1. Schematic of column leach test setup. 110

112 111 Effluent Collection Columns Influent Influent Tubes Flow Pump Figure 4.2. Photograph of columns, flow pump, and influent container.

113 112 Effluent Collection Bag Effluent Ports Figure 4.3. Photograph of top of column, showing effluent end of column with sample collection bag.