Preserving Ground Water Samples With Hydrochloric Acid Does Not Result in the Formation of Chloroform |
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| Authors: | Paul J Squillace James F Pankow Jack E Barbash Curtis V Price John S Zogorski |
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| Institution: | 1. Paul J. Squillace is a research hydrologist for the Volatile Organic Chemical National Synthesis Project which is being completed by the U.S. Geological Survey as part of the National Water-Quality Assessment Program (USGS, 1608 Mt. View Rd., Rapid City, SD 57702, e-mail: pjsquill@usgs.gov). He has been working for the U.S. Geological Survey for the past 13 years and has experience in ground water flow modeling and the fate and transport of organic chemicals in shallow ground water. His M.S. degree (geology) is from the University of Minnesota at Duluth and his B.A. degree (geology) is from Winona State College.;2. James F. Pankow is professor and head of the Department of Environmental Science and Engineering at the Oregon Graduate Institute (e-mail: pankow@ese.ogi.edu). He received his B.A. in chemistry in 1973 from the State University of New York in Binghamton, and his Ph.D. in environmental engineering science from the California Institute of Technology in Pasadena, California, in 1979. His group is involved in the study of the physical and chemical processes affecting the behavior of organic and inorganic chemicals in the environment. This work includes the development and application of sensitive analytical methods for the determination of trace organic contaminants in air and ground water.;3. Jack E. Barbash (e-mail: jbarbash@usgs.gov) is a research chemist for the Pesticide National Synthesis Project. He has worked for the U.S. Geological Survey since 1991, focusing primarily on the sources, occurrence, and fate of pesticides in ground water, as well as on the general design of ground water sampling studies for the National Water-Quality Assessment Program. He obtained his Ph.D. degree from Stanford University (environmental engineering and science), his M.S. degree from the University of Waterloo, Canada (hydrogeology), and his A.B. degree from Harvard University (earth sciences).;4. Curtis V. Price (e-mail: cprice@usgs.gov) is a physical scientist for the Volatile Organic Chemical National Synthesis Project. He has worked for the USGS as a specialist in data analysis and geographic information systems since 1987. His M.S. degree is from Dartmouth College (geology) and his B.S. is from University of Puget Sound (geology).;5. John S. Zogorski (e-mail: jszogors@usgs.gov) is chief of the Volatile Organic Chemical National Synthesis Project. He has worked for the U.S. Geological Survey since 1992, and previously held a variety of academic positions. His Ph.D. and M.S. degrees are from Rutgers University (environmental sciences), and his B.S. degree is from Drexel University (civil engineering). |
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| Abstract: | Water samples collected for the determination of volatile organic compounds (VOCs) are often preserved with hydrochloric acid (HCl) to inhibit the biotransformation of the analytes of interest until the chemical analyses can he performed. However, it is theoretically possible that residual free chlorine in the HCl can react with dissolved organic carbon (DOC) to form chloroform via the haloform reaction. Analyses of 1501 ground water samples preserved with HCl from the U.S. Geological Survey's National Water-Quality Assessment Program indicate that chloroform was the most commonly detected VOC among 60 VOCs monitored. The DOC concentrations were not significantly larger in samples with detectable chloroform than in those with no delectable chloroform, nor was there any correlation between the concentrations of chloroform and DOC. Furthermore, chloroform was detected more frequently in shallow ground water in urban areas (28.5% of the wells sampled) than in agricultural areas (1.6% of the wells sampled), which indicates that its detection was more related to urban land-use activities than to sample acidification. These data provide strong evidence that acidification with HCl does not lead to the production of significant amounts of chloroform in ground water samples. To verify these results, an acidification study was designed to measure the concentrations of all trihalomethanes (THMs) that can form as a result of HCl preservation in ground water samples and to determine if ascorbic acid (C6H8O6) could inhibit this reaction if it did occur. This study showed that no THMs were formed as a result of HCl acidification, and that ascorbic acid had no discernible effect on the concentrations of THMs measured. |
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