Geochemical Heterogeneity of Groundwater in Uncontaminated and Contaminated Aquifers

1. Geochemical Heterogeneity of Groundwater in Uncontaminated and Contaminated Aquifers Jean M. Bahr University of Wisconsin - Madison

2. Hydrogeologists expect spatial variations in concentrations at contaminated sites “A” Aquifer Water Levels and TCE Plumes, 1983

3. But “background” concentrations often determined by a single upgradient well Background well

4. Take Home Messages • Groundwater chemistry at “pristine” sites can vary temporally and spatially at local scales • Geochemical signatures can help to delineate local flow paths • Geochemical heterogeneity at a local scale reflects a combination of distinct flow paths and reactions

5. Case Studies • Discharge zone in WI Central Sands • Discharge zones in a glacial aquifer of Northern WI • Fractured dolomite in Door Co., WI • Fractured shale at Oak Ridge, TN • Pristine and plume transects at a site of BTEX contamination near Sparta WI

6. Current and Former Students • Lucy Chambers Meigs • Lynn Raue Dean • Rod Rustad • Elizabeth Keating • Gerilynn Moline • Madeline Schreiber • Jodi Vandervelden • Maureen Muldoon • Peter Taglia • Ingrid Ekstrom Geology 729 Classes

7. Discharge zone in Wisconsin’s Central Sands

8. Lucy Chambers Meigs

9. Multilevel Construction and Installation

10. Miniature Multilevel Installation Completed Miniature Multilevels

11. Field sampling and analysis

12. Colorimetric kits for DO, Fe, NO3 and others

13. Ditch Injection Well

14. 64 58 Elevation (ft)

17. (mg/l) (mg/l) (mg/l) Elevation (ft)

18. (mg/l) (mg/l) (mg/l) Elevation (ft)

19. Elevation (ft)

20. Elevation (ft)

21. Elevation (ft) Elevation (ft)

22. Discharge zones in a glacial aquifer of Northern Wisconsin

24. Elizabeth Keating Middle Site Lower Site

27. Reactions Simulated Dissolution Plag + 5 H+  Ca2+ + clay + 3[cations]+ Fe(OH)3 +3H+  Fe3+ + 3H2O Acid/Base CO32- + H+  HCO3- H2CO3  HCO3- + H+ Redox Fe2+  Fe3+ + e- 1/2 O2 + 2H+ + 2e-  H2O

28. Calibration Parameters • Hydraulic conductivity zones • Plagioclase dissolution rate constant • Electron source rates for different electron acceptors

29. Middle Site Streambed + Hillslope Upper Site Lower Site Streambed + Hillslope

30. 1 0 9 4

31. Elevation (m)

32. Fractured dolomite in Door Co., Wisconsin

34. Bissen Quarry Maureen Muldoon Fracture Mapping

36. Elevation (ft)

38. Chloride (mg/l)

39. Fractured shale at Oak Ridge, Tennessee

40. Water table Shallow bedrock a) grid N grid N true N true N Horizontal gradient 45 vector mean=200 vector mean=180 b) grid N grid N true N true N 45 Horizontal flow direction vector mean=249 vector mean=180

42. Ca-HCO3 Ca-Na-HCO3 Na-Ca-HCO3 Na-Ca-HCO3-SO4 Na-HCO3 Pine Ridge sample mixing line January 1995 July 1995 Ca-Mg-SO4 Ca-Mg-SO4 Ca+Mg Ca+Mg SO4+Cl SO4+Cl Mg Mg SO4 SO4 Na+K HCO3+CO3 Na+K HCO3+CO3 Ca Na+K HCO3+CO3 Cl Ca Na+K HCO3+CO3 Cl cations anions cations anions Hydrochemical Facies from Multilevel Samples

43. Spatial Distribution of Hydrochemical Facies

45. Approx. horizontal flow direction

47. BTEX plume in sandy aquifer, Fort McCoy

48. Maddy Schreiber Pete Taglia

49. Locations of Uncontaminated and Contaminated Transects Tarr Creek

50. Uncontaminated Transect Elevation (m) Elevation (m)