Low-Flow Purging and Sampling of Ground Water Monitoring Wells with Dedicated Systems |
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| Authors: | Robert W Puls Cynthia J Paul |
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| Institution: | Robert W. Puls;is currently employed at the R.S. Kerr Environmental Research Laboratory (RSKERL), U.S. EPA, Subsurface Systems Branch, in the Research Division (Acta, OK 74820). He received his Ph.D. in soil and water science from the University of Arizona. Following completion of his doctorate he worked on the High Level Nuclear Waste Repository Research Program (DOE) investigating the fate and transport of radionuclides in ground water. He has been employed at RSKERL since 1987. Recent topics of particular interest include the following: surface chemical factors which influence colloidal stability and transport in subsurface systems, surface redox-mediated transformations of inorganic contaminants in soils and ground water, in situ remediation of contaminated metals sites, and the development of ground water sampling techniques that provide representative and reproducible contaminant concentrations for the purposes of risk assessment remedial performance at hazardous waste sites. Cynthia J. Paul;is currently employed by the U.S. EPA at RSKERL. She received her bachelor's degree from East Central University in 1990 and will complete her master's degree in environmental science at the University of Oklahoma in 1995. Her research interests include adsorption-desorption and oxidation-reduction reactions of inorganics as related to subsurface contaminant fate and transport. Other interests include ground water sampling methodologies and turbidity effects on volatile organic contaminants. |
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| Abstract: | A field study was conducted to assess purging requirements for dedicated sampling systems in conventional monitoring wells and for pumps encased in short screens and buried within a shallow sandy aquifer. Low-flow purging methods were used, and wells were purged until water quality indicator parameters (dissolved oxygen, specific conductance, turbidity) and contaminant concentrations (chromate, trichloroethylene, dichloroethylene) reached equilibrium. Eight wells, varying in depth from 4.6 to 15.2 m below ground surface, were studied. The data show that purge volumes were independent of well depth or casing volumes. Contaminant concentrations equilibrated with less than 7.5 I. of purge volume in all wells. Initial contaminant concentration values were generally within 20 percent of final values. Water quality parameters equilibrated in less than 10 L in all wells and were conservative measures for indicating the presence of adjacent formation water. Water quality parameters equilibrated faster in dedicated sampling systems than in portable systems and initial turbidity levels were lower. |
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