Field Measurement of Dissolved Oxygen: A Comparison of Methods |
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| Authors: | Richard T Wilkin Mary S McNeil Cherri J Adair John T Wilson |
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| Institution: | Richard T. Wilkin is an environmental scientist with the National Risk Management Research Laboratory (U.S. EPA, Office of Research and Development, P.O. Box 1198, Ada, OK 74820;). His research interests focus on transport and fate processes and geochemical modeling in natural, contaminated, and redox-manipulated ground water systems. He received a Ph.D. in geosciences from the Penn State University.;Mary S. McNeil is an environmental scientist with the National Risk Management Research Laboratory (U.S. EPA) in Ada, Oklahoma. She has a B.S. in mathematics from East Central University and an M.S. in environmental science from the University of Oklahoma. She is currently involved in research that addresses the treatment of acid mine drainage and the long-term performance of in situ permeable reacti e barriers.;Cherri J. Adair is an environmental scientist at the Robert S. Kerr Environmental Research Center (of the National Risk Management Research Laboratory, U.S. Environmental Protection Agency) in Ada, Oklahoma. She has a B.S. in biology from East Central University. She conducts microcosm studies on the bio-transformation of MTBE and chlorinated solvents.;John T. Wilson is a senior research microbiologist with the National Risk Management Research Laboratory (U.S. EPA). He has more than 20 years of experience with issues of quality control associated with sampling contaminated ground water. He was a principal author of EPA's Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water. |
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| Abstract: | The ability to confidently measure the concentration of dissolved oxygen (D.O.) in ground water is a key aspect of remedy selection and assessment. Presented here is a comparison of the commonly practiced methods for determining D.O. concentrations in ground water, including colorimetric, membrane-covered electrode, and modified Winkler techniques. The Winkler titration (azide and permanganate modifications) is the most accurate and precise technique for determining D.O. and is appropriate for applications with stringent data quality objectives. In addition, excellent correlation over a wide range of D.O. concentrations was found between Winkler titrations and colorimetric tests using the rhodazine D (below 1 part per million ppm]) and indigo carmine reagents (above 1 ppm). Electrode measurements represent the simplest method for determining D.O. concentrations on a continuous basis and electrode determinations positively correlate with Winkler results above 1 ppm. Below 1 ppm, electrodes provide only a qualitative measure of low D.O. level, apparently due to slow electrode response. |
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