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Transport and Degradation of a Trichloroethylene Plume Within a Stream Hyporheic Zone

  • John B. Williams
  • Gary Mills
  • Daniel Barnhurst
  • Sherry Southern
  • Noelle Garvin
Conference paper

Abstract

In predicting natural attenuation rates for contaminant plumes, it is vital to determine flow patterns, suitability of chemical and microbial conditions, and seasonality. Savannah River Site’s CMP Pits operated from 1971 until 1979; receiving chemicals, metals, and pesticides. Now a Superfund site, monitoring-wells indicated perchloroethylene (PCE) and trichloroethylene (TCE) had seeped beneath the vadose zone. It was unknown how the plume was entering Pen Branch valley below and whether natural attenuation was degrading the contaminant load. Our study focused on plume transport and exchange within the critical hyporheic zone beneath Pen Branch and helped to ground-truth model the plume borders. We also determined reductive dechlorination of PCE and TCE into dichloroethylene and vinyl chloride. Over forty sampling holes were augered into the hyporheic zone and adjacent floodplain along with 12 stream stations. Chemical conditions linked to natural attenuation (e.g. H2S, Fe+2, and NH3) were monitored to identify reductive dechlorination suitability along with temperature, pH, redox, and dissolved oxygen. Plume flow displayed complex entry patterns, but natural attenuation was documented by higher levels of cis-dichloroethylene (cis-DCE) (61.5 μg/l) compared to PCE or TCE. High means of hyporheic PCE (26.5 μg/l) and TCE (6.7 μg/l) compared to overlying stream water PCE (0.5 μg/l) and TCE (0.2 μg/l) raise new transport pathway questions.

Keywords

Volatile Organic Compound Natural Attenuation Hyporheic Zone Reductive Dechlorination Savannah River Site 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

The efforts of South Carolina State University student interns: Chris Carter, Stephanie Roach, Landis Chambers, Kendall Simmons, Ta’mara Brown, Lanita Peterson, and Eric Foxworth were greatly appreciated. University and SRS planning assistance were also given generously by Dr. Judith D. Salley, Larry Anderson, and Janelle Jansen.

References

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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • John B. Williams
    • 1
  • Gary Mills
    • 2
  • Daniel Barnhurst
    • 3
  • Sherry Southern
    • 4
  • Noelle Garvin
    • 2
  1. 1.Department of Biological & Physical SciencesSouth Carolina State UniversityOrangeburgUSA
  2. 2.University of Georgia SRELAikenUSA
  3. 3.Washington Savannah River CorporationAikenUSA
  4. 4.U.S. DOEAikenUSA

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