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Some Biases in Sampling Multilevel Piezometers for Volatile Organics |
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| Authors: | J. F. Barker G. C Patrick L. Lemon G. M. Travis |
| Affiliation: | James F. Barker is an associate professor in the Department of Earth Sciences, University of Waterloo (Waterloo, Ontario, Canada, N2L 3G1). He obtained his Ph. D. from Waterloo in 1979 and has been at Waterloo since then. His main research interests include petroleum geochemistry, organic geochemistry of ground water, and chemical and biological aspects of organic contaminant transport in ground water. He is a member of the Institute for Ground Water Research at Waterloo.;Guy C. Patrick completed his M. Sc. in hydrogeology at the University of Waterloo in 1986. His research addressed the migration of petroleum-derived organics in ground water. He has degrees in biology and in applied science (environmental systems) from the University of Regina and is currently employed as a hydrogeologist with Golder Associates (4104, 148th Ave. NE, Seattle, WA 98052).;Lloyd A. Lemon obtained his B. Sc. in applied earth sciences (Co-op option) from the University of Waterloo in 1982. He has held various geological and hydrogeological positions since graduating, including a position as a hydrogeochemical technician involved in organic contaminant studies at Waterloo. He is currently a geological technician with Conestoga—Rovers andAssociatesLtd., (651 Colby Dr., Waterloo, Ontario, Canada N2V 1 C2).;Gary U. Travis obtained his B. Sc. in earth sciences from the University of Waterloo in 1985. His B. Sc. thesis examined sources of bias in volatile organic contaminant data from ground water. He is currently studying environmental law in the Faculty of Law, University of Windsor, Windsor, Ontario, Canada. |
| Abstract: | Multilevel piezometers are cost-effective monitoring devices for determining the three-dimensional distribution of solutes in ground water. Construction includes flexible tubing (plastic or Teflon®). Their sampling is subject to a number of'potential biases, particularly: (1) losses of volatile organic solutes via volatilization, (2) sorption onto the flexible tubing of the piezometers, (3) leaching of organics from this tubing, and (4) collection of unrepresentative samples due to inadequate piezometer flushing. It is shown that these biases are minimal or are easily controlled in most situations. Another source of bias has been recognized. Organic solutes present in ground water above the screened level can penetrate the flexible plastic or Teflon tubing and contaminate the sampled water being drawn through this tubing. Laboratory tests and field results indicate this transmission causes low organic contaminant concentrations to be erroneously attributed to ground water which is free of such contaminants. The transmitted organics apparently desorb from the plastic tubing during flushing of even 40 piezometer volumes. Recognition of this transmission problem provides for a better interpretation of existing organic contaminant distribution data. Caution is advised when considering the use of these monitoring devices in organic solute contaminant studies. |
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