1. 1960 1995 Ground Water Age and Chemistry Data along Flow Paths: Implications for Trends and Transformations of Nutrients and Pesticides Jim Tesoriero, Karen Burow, Betsy Frick, David Saad, Larry Puckett U.S. Geological Survey

2. Increased influx of nutrients and pesticides  Five-fold increase in nitrogen fertilizer applied since 1960  Commonly used herbicides introduced  What are the implications for ground water quality? Millions of Metric Tons Per Year N Fertilizer Atrazine Alachlor Pesticides Introduced: Metolachlor

3. NO 3 - →N 2 Study Objectives: 1) Determine and explain trends in concentrations. 2) Determine where transformations occur. 1990 1985 1980 1975 1970 1950 2000 1960 1970 1. Determine recharge dates of ground water along flow paths Design: 2. Characterize water chemistry and natural attenuation 3. Compare constituent concentrations to loading history Nutrient and Pesticide Application

4. Reactions Redox Zone DO NO 3 - or N 2 Iron Aerobic Respiration: O 2  H 2 O OxicHighNO 3 - Low Denitrification: NO 3 -  N 2 Nitrate- reducing Low NO 3 -  N 2 Low Ferric Iron Reduction: Fe 3+  Fe 2+ Iron- reducing LowN2N2 High Natural Attenuation: Redox Reactions Important in Determining Fate of Constituents Water Chemistry

5. Western Lake Michigan Drainages Wisconsin Albemarle- Pamlico Basin North Carolina Apalachicola- Chattahoochee- Flint River Basin Georgia Investigate the Influence of Hydrogeologic Setting on Contaminant Fate Eastern San Joaquin Valley California Unsaturated Zone ThinThick Oxic Zone In Ground Water Thin North Carolina ------ ThickGeorgia Wisconsin California

6. Nitrate concentrations are high but limited to upper few meters.Downstream impacts are limited by denitrification. North Carolina: Nitrate Concentrations and Fate Oxic Nitrate Reducing Iron Reducing 10 mg/L <1 mg/L

7. Use of Residence Times to Understand Chemical Evolution of Ground Water Low Nitrate, High Denitrification High Nitrate, No Denitrification Low Nitrate, Low Denitrification

8. Wisconsin: Nitrate Concentrations and Fate High nitrate concentrations in top 10 m of saturated thickness. Oxic conditions suggest significant downstream impacts on ground water and streams likely. Oxic 8 mg/L

9. Larger Oxic Zone at Wisconsin Site is Due to Slower O 2 Consumption Rates than at NC Site Wisconsin North Carolina Dissolved O 2 Consumption (mg/L) NC: 0.36 mg O 2 /L per yr WI: 0.18 mg O 2 /L per yr

10. Recharge Nitrate Concentrations Increase From 1960 to 2000 Recharge [NO 3 - ] (mg/L as N) 195019601970198019902000 North Carolina Note: 1) Independent variable in regression equations is years since 1940. 195019601970198019902000 Wisconsin R 2 =0.88 R 2 =0.33 Recharge Nitrate Concentrations =[NO 3 - ]+[N 2 from denitrification] Recharge [NO 3 - ] (mg/L as N) Recharge Year

11. Nitrate Concentration Increases Are Consistent with Fertilizer and/or Manure Usage Wisconsin North Carolina Nitrogen Use (kg/acre) Fertilizer Manure [NO 3 - ] Recharge [NO 3 - ] (mg/L as N)

12. Nitrate Concentrations in Ground Water Explained by 30% of Fertilizer Applied Wisconsin 30 % of applied N Applied N dissolved in 21 cm of recharge applied to cropped area of county. [NO 3 - ] in ground water Recharge [NO 3 - ] (mg/L as N)

13. Trends From This Study Agree with Larger Spatial Study Land Use Study Flow System Study

14. Pesticide Trends and Transformations  Relate atrazine concentrations to: - crops planted in the county - atrazine use rate  Examine parent and degradate concentrations of atrazine.  Similar findings for metolachlor and alachlor and their degradates.

15. Georgia: Land Use Changes Related to Increase and then Decrease in Atrazine + DEA? Atrazine+DEA % Corn & Soybean

16. LocalAtrazineBan Wisconsin: -Atrazine or Deethylatrazine Found in All Samples -Effects of Atrazine Ban Not Observed Yet

17. Ground Water Age (years) Deethylatrazine (DEA) Mole Fraction Deethylatrazine Dominant at Sites with Thick Unsaturated Zones but Not at Sites with Thin Unsaturated Zones -Suggests Degradation Occurs Primarily in the Unsaturated Zone All Deethylatrazine All Atrazine DEA=Atrazine Thick unsaturated zones Thin unsaturated zones Wisconsin California North Carolina Georgia

18. Summary Coupling age dating with water chemistry data improves our understanding of: The Linkage Between Land Use Practices and Water Quality Trends in Constituent Concentrations Transformation Rates of Constituents

19. Contact Information  Jim Tesoriero: tesorier@usgs.govtesorier@usgs.gov  Karen Burow: krburow@usgs.govkrburow@usgs.gov  David Saad: dasaad@usgs.govdasaad@usgs.gov  Elizabeth Frick: eafrick@usgs.goveafrick@usgs.gov  Larry Puckett: lpuckett@usgs.govlpuckett@usgs.gov