Migration of Heavy Metals from Simulated Small Arms Firing Berms

Transcription

1 Migration of Heavy Metals from Simulated Small Arms Firing Berms W. Andy Martin Environmental Engineer, ERDC Steven L. Larson Research Chemist, ERDC Steven R. Hearne Senior Fellow Army Environmental Policy Institute JSEM Conference 22 Mar 06

2 Project Overview & Objectives AEPI coordinated effort with ARDEC Heavy Metals Office (HMO) Advance knowledge of heavy metals, e.g., tungsten, transport mechanisms from SAFRs Provide for more informed decision making supporting: Follow-on transport [e.g., field sampling and field lysimeter] studies Improved SAFR management and design Selection of next generation ammo Specific Study Objectives: Evaluate long-term stability of tungsten on SAFR using Green Bullet Simulated berm soils exposed to one year s worth of rain events Assess tungsten loss [mass] or release from differing SAFR soils: Runoff [surface water] and leachate [ground water] Dissolved [soluble] and particulate forms

3 Firing Particle size and metal distribution Mixing and splitting of soil

4 Simulated Berm Material ARDEC HMO and Environmental Technology Division made the soils fired on with tungsten-nylon rounds at ERDC s Big Black testing facility available for this laboratory lysimeter study This leveraging of research material allowed for a low cost, high knowledge gain project funded by AEPI Firing Mixing and splitting of soil

5 Study Approach - Considerations Batch Testing Provides first-level approximation of potential mobility Simulated soils Lowest cost Lab Lysimeter Better mimics field conditions in accelerated/controlled system [e.g., weeks versus months] Like batch use simulated soils Unlike batch - allows sampling of simulated leachates & runoffs Correlates well with field efforts [based on past metals studies] Moderate cost Field Sampling & Lysimeter Use actual soils Actual site conditions High cost Limited control of experimental variables

6 Background Bullet Composition Jacket Copper & Zinc Steel Core -Iron Lead Slug Lead & Antimony Tungsten Slug Tungsten micron sized metal particles pressed with Nylon

7 Weights of 5.56-mm (M855) Bullet Components* Component Bullet Jacket 1 Steel Core 2 Nomenclature Mass (grams) Mass (grams) Composition Copper alloy Steel Weight (grains) Copper (90.0%) Iron (98.0%) Individual materials Zinc (9.9%) Manganese (0.75%) Lead (0.05%) Carbon (0.47%) Iron (0.05%) Sulfur (0.05%) Phosphorus (0.04%) Component Lead Slug Tungsten Slug Nomenclature Mass (grams) Mass (grams) Composition Pb-Sb alloy Tungsten-nylon Weight (grains) Individual materials Lead (99.0%) Tungsten (97.0%) Antimony (1.0%) Nylon (3.0%) * DefenseAmmunition Center 2005

8 Background Tungsten Formulations Rat Study Relative Amount of W in Composition Tungsten-Nylon Tungsten-Tin W-Ni-Co/ W-Ni-Fe Tungsten steels W Surface area for W-water reaction W +4 H 2 O WO H e- Lower ph Water Soluble Ion [Tungstate Anion]

9 Methodology Lysimeter System Cross-section of lysimeter. Empty lysimeter cell showing runoff and leachate collection systems

10 Methodology - Experimental Design C1 C2 C3 C4 C5 C6 C7 Clay Silty Sand A Glacial Till Silty Sand B Peat Loess Silt Loess Silt [Lead] tungsten-nylon tungsten-nylon tungsten-nylon tungsten-nylon tungsten-nylon tungsten-nylon lead Soils- 6 Soil types fired on using tungsten-nylon 5.56 mm and lead 5.56 mm rounds at a distance of 25 meters to control fragmentation; 10,000 mg/kg Rain- 16 weekly rain events (1.5 inches per rain) to simulate annual rainfall Sampling- Leachate & runoff samples analyzed for total and soluble metals Total- digested water sample with suspended solids Soluble- filter (0.45 micrometer) water Analysis Leachate & runoff were analyzed for 11 metals representative of constituents found in the tungsten-nylon and lead bullets

11 Methodology - Laboratory Layout Layout of the experiment at the Hazardous Waste Research Center in Vicksburg, MS.

12 Metals leaving the Lysimeters over 16 Rain Events Six metals were noted to migrate from the lysimeters: W, Cu, Pb, Fe, Mn, Zn W, Cu, and Pb are discussed in more detail Mass of Fe, Mn and Zn Measured Leaving the Seven Lysimeters 1 Soil Type Lysimeter Sum of Metal Mass in Leachate and Runoff in grams Fe Mn Zn Clay C Silty sand A C Glacial till C Silty sand B C Peat C Loess silt C Loess siltlead C

13 Key Results Percentage of Tungsten and Lead Leaving the Lysimeters Over 16 Weekly Rain Events Percentage of Initial Mass Leaving the Systems % 10.00% 1.00% 0.10% 0.01% 0.00% 13.60% 13.40% 11.35% Glacial till Silty Sand A Silty Sand B 0.09% 0.08% 0.07% Tungsten Lead 0.004% Clay Peat Loess Silt Loess Silt-Lead Simulated Berm Soil Prepared by Firing Tungsten or Lead Rounds at 25 m

14 Background Physical Forms Lead Fragment - Discreet Particle [small surface to mass ratio] Tungsten Smear - Particles Coating Soil [high surface to mass ratio]

15 Soil Type Dependence on Tungsten Leachability Total Mass of Tungsten in Digested Runoff and Leachate Total Mass of Tungsten in Digested Runoff and Leachate Tung sten M ass in G ram s Silty sand A Glacial till Silty sand B Tung sten M ass in G ram s Clay Peat Loess silt Loess silt-lead Weekely Rain Events (weeks) Weekely Rain Events (weeks)

16 Filtered (0.45 micron) or Soluble Tungsten in Leachate Mass of Tungsten in Filtered Leachates Tungsten Mass in Grams Clay Silty sand A Glacial till Silty sand B Peat Loess silt Loess silt-lead Weekely Rain Events (weeks) Mass of Tungsten in Filtered Leachate 1.5 Tungsten Mass in Grams Clay Peat Loess silt Loess silt-lead Weekely Rain Events (weeks)

17 Soluble Tungsten in Runoff Mass of Tungsten in Filtered Runoffs Tungsten Mass in Grams Clay Silty sand A Glacial till Silty sand B Peat Loess silt Loess silt-lead Weekely Rain Events (weeks) Mass of Tungsten in Filtered Runoff Tungsten Mass in Grams Clay Peat Loess silt Loess silt-lead Weekely Rain Events (weeks)

18 Copper Migration Total Mass of Copper Leaving the Lysimeter 1.4 Copper Mass in Grams Clay Silty sand A Glacial till Silty sand B Peat Loess silt Masses Loess silt-lead of Copper and Tungsten Leaving the Lysimeter over the 16-Week Procedure and Ratio of Masses Weekely Rain Events (weeks) Soil Type Lysimeter Cu Mass Leaving g W Mass Leaving g Ratio W mass: Cu mass Copper and Tungsten are both present in the Tungsten-nylon round the ratio of tungsten mass to copper mass leaving the cell ranges from 50 to 1087 Clay C Silty sand A C Glacial till C Silty sand B C Peat C Loess silt C

19 Lead Mass in Grams Lead Migration No lead was detected above 50 mg/l in any of the leachates or runoffs from the seven lysimeters. Particulate lead was measured in the leachates and runoffs from the lysimeters Weekely Rain Events (weeks) Lead mass exiting the cell as particulates in runoff was greater than observed from the leachate digests Mass of lead in Digested Leachates Lead Mass in Grams Clay Silty sand A Glacial till Silty sand B Peat Loess silt Loess silt-lead Mass of Lead in Digested Runoff Weekely Rain Events (weeks) Relatively small masses of particulate lead was noted leaving via leachate Clay Silty sand A Glacial till Silty sand B Peat Loess silt Loess silt-lead

20 Summary of Findings Tungsten behaves significantly different from lead and copper in both leachate and runoff Lead and copper transported primarily as particulates Tungsten migration [approx. half] is in dissolved [soluble] state Observed rapid corrosion of tungsten into mobile species Strong positive dependence between type of soils [permeability] and dissolved tungsten migration Large mass of tungsten loss in lysimeters containing berm soils with unified soil class SM, e.g., silty sand A, silty sand B, and glacial till Tungsten-nylon residues in high permeability soils can act as sources for tungsten in runoff and leachate water

21 Questions?