Using Basic Chemistry in Interpreting Water Source, Age, and Trends KIMM CRAWFORD

Transcription

1 Using Basic Chemistry in Interpreting Water Source, Age, and Trends KIMM CRAWFORD

2 Inver Grove Heights

3 Galena Aquifer Prairie du Chien Aquifer

4 Inver Grove Heights Manganese Study Almost three-quarters of the 274 Inver Grove Heights wells exceeded the manganese health advisory level of 0.05 mg/l. Additional parameters included anions (nitrate, chloride, and sulfate), iron, dissolved oxygen, conductivity, ph, and bacteria. No wells exceeded the 10 mg/l NO3-N standard. Because almost half of wells had high CSMR ratios, follow up data collection for lead has been undertaken.

5 Chloride Sulfate Mass Ratio (CSMR) A Cl:SO4 mass ratio of greater than 0.58 has been shown to be associated with high lead levels in water. Fraction of wells exceeding a Cl:SO4 ratio of 0.58: Inver Grove Heights: 47% of 274 wells Hastings Municipal Wells: 4 of 8 wells SE Minnesota: 28% of 1,665 samples Olmsted County: 23% of 8,074 wells Rochester Public Utilities: 3 of 33 wells Cl is increasing and SO4 is decreasing in SE MN

6 Flint Michigan Water Problems Flint Michigan is in the news daily for its water quality problems. One of which is high lead levels. Lead levels are a consequence of old lead pipes and the lack of corrosion control after changing water sources. The lead corrosion problem is directly related to the chloride and sulfate levels in the water.

7 Minnesota Road & Softener Salt Use (Mtons/Yr) MN DOT of Salt (Mtons) vs year Salt (tons) year

8 Minnesota Potash (KCl) Use on Corn (lbs/acre)

9 US SO2 Emissions (Gtons/Yr) Rochester Rainfall 2001 Median (mg/l) Sulfate (SO4) 1.9 Chloride (Cl) 0.7 Nitrate (NO3-N) 0.2 Fluoride (F) <0.1

10 Dakota County Ambient Groundwater Quality Study About 15 years of testing of 76 residential wells Wide variety of parameters (field parameters, anions, cations, trace elements, herbicides, other contaminants of current concern) A quarter of wells exceed the 10 mg/l NO3-N standard Cl:NO3-N ratios correlate with land cover higher ratios in developed areas and lower in agricultural areas Ca:Mg ratios which in Dakota County are typically less than two typical of dolomite

11 Cl:NO3-N Ratios in Agriculture Tile drainage in corn, corn-soybean rotations has a Cl:NO3- N ratio of about 2:1. At 70% N fertilizer use efficiency in corn, Cl from potash (KCl) to N is about 2:1. This provides a simple physical interpretation of the ratio in tile or groundwater. Tile Drainage Mg Ca Cl NO3-N SO4 Na K Cl:NO3-N Ca:Mg

12 Cl:NO3-N Ratios in Inver Grove Heights Only 88 of 274 wells had detectable NO3-N (<0.2 mg/l) Highest NO3-N was 6 mg/l Wells with NO3-N > 1.0 mg/l had a median Cl:NO3-N ratio of 14:1 This reflects the NaCl contribution from road salt and/or softener salt Na levels can help distinguish the Cl source (NaCl vs KCl) Background Na in groundwater is about 2 to 5 mg/l Inver Grove Mg Ca Cl NO3-N SO4 Na Cl:NO3 Ca:Mg AGQS AGQS

13 Minnesota Nitrogen Use on Corn (lbs/acre)

14 Avg. Nitrate (mg/l) Whitewater River NO3-N (mg/l) 1967 to 2010 Nitrate Trends MPCA

15 Whitewater River Cl (mg/l) 1967 to

16 Whitewater River SO4 (mg/l) 1967 to

17 Douglas Water Well NO3-N (mg/l) vs Nitrogen Fertilizer Use ~ 40 year time lag

18 Douglas Water Well Cl (mg/l) vs Salt and Potash Use ~ 40 year time lag

19 Douglas Water Well SO4 (mg/l) vs SO2 Emissions ~ 40 year time lag

20 Conversion from Agriculture to Urban Land Use 2000 to 2004 Galena Aquifer Monitoring Well

21 Conversion from Agriculture to Urban NO3-N(mg/l) Date Mg Ca Cl NO3-N SO4 Na Cl:NO3 Ca:Mg 12/15/ /15/

22 Biofilter NO3-N(mg/l) Date Site CL NO3 NO3 Reduction SO4 SO4 Reduction Cl:NO3_N 6/8/15 Up /8/15 Down % 17 11% 39 8/20/15 Up /20/15 Down % < % 62

23 Whitewater Stream and Springs NO3-N(mg/l) Lab # Source NO3-N OCSS1 Spring 4 OCSS19 Spring 4 OCSS4 Spring 8.3 OCSS20 Stream 8.6

24 Whitewater Stream and Springs Anions (mg/l) Lab # Source NO3-N Cl F SO4 Cl:NO3 OCSS1 Spring < OCSS19 Spring OCSS4 Spring < OCSS20 Stream

25 Whitewater Stream and Springs Anions and Cations Lab # Source NO3-N Mg Ca Cl F SO4 Na K Cl:NO3 Ca:Mg OCSS1 Spring < OCSS19 Spring OCSS4 Spring < OCSS20 Stream

26 Summary Single parameter data sets answer simple questions Ca:Mg Ratio Galena vs Prairie du Chien water source Cl:SO4 Ratio (CSMR) corrosion and lead Cl:NO3-N Ratio urban vs agricultural water source Na distinguish Cl source (KCl vs NaCl) F municipal water source NO3-N, Cl, SO4 and Na trends over time water age NO3-N, Cl, SO4 and Na trends land use changes NO3-N, Cl and SO4 biofiltration processes