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Influence of Casing Materials on Trace-Level Chemicals in Well Water |
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| Authors: | Louise V Parker Alan D Hewitt Thomas F Jenkins |
| Institution: | Louise V, Parker is a research physical scientist at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) (72 Lynte Rd, Hanover, NH 03755–1290). She received her B.A. in microbiology from the University of New Hampshire and her M.S. in food microbiology from the Department of Food Science and Nutrition at the University of Massachusetts. Her research interests include environmental microbiology and chemistry. She is a member of the AGWSE and has been active in ASTM Subcommittee D18.21 on Ground Water and Vadose Zone Investigations.;Alan D. Hewitt is also a research physical scientist at CRREL (72 Lyme Rd, Hanover, NH 03755–1290). He has a B.A. in chemistry from the University of New Hampshire and an M.S. in chemical oceanography from the University of Connecticut. His areas of interest are inorganic hazardous waste chemistry and the chemistry of ice and snow.;Thomas F. Jenkins is a research chemist at CRREL (72 Lyme Rd., Hanover, NH 03755–1290). He received his B.S. in chemistry from the University of Missouri at St. Louis, his M.S. in chemistry at the University of Colorado, and his Ph.D. in chemistry at the University of New Hampshire. His research interest is environmental analytical chemistry. |
| Abstract: | Four well casing materials — polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), and stainless steel 304 (SS 304) and 316 (SS 316) — were examined to determine their suitability for monitoring inorganic and organic constituents in well water. The inorganic study used a factorial design to test the effect of concentration of mixed metals (arsenic As], chromium Cr], lead Pb], and cadmium Cd]), pH, and organic carbon. Sample times were 0.5, 4, 8, 24, and 72 hours. Except for slow loss of Pb, PTFE well casings had no significant effect on the concentration of metals in solution. For the other casings, changes in analyte concentration often exceeded 10 percent in eight hours or less and, thus, could bias analyses of samples taken from wells constructed with these materials. Specifically, PVC casings sorbed Pb and leached Cd; SS 316 casings sorbed As and Pb and leached Cd; and SS 304 casings sorbed As, Cr, and Pb and leached Cd. Both stainless steel casing materials showed markedly poorer performance than the PVC casings. The well casings were also tested for sorption/desorption of 10 organic substances from the following classes: chlorinated alkehes, chlorinated aromatics, nitroaromatics and nitramines. Sample times were 0, 1, 8, 24, and 72 hours, seven days, and six weeks. There were no detectable losses of analytes in any of the sample solutions containing stainless steel well casings. Significant loss of some analytes was observed in sample solutions containing plastic casings, although losses were always more rapid with the PTFE casings than with PVC. Chlorinated organic substances were lost most rapidly. For samples containing PTFE casings, losses of some of these compounds were rapid enough (>10 percent in eight hours) to be of concern for ground water monitoring. Losses of hydrophobic organic constituents in samples containing PTFE casings were correlated with the compound's octanol/water partition coefficient. |
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