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Natural Attenuation of Aromatic Hydrocarbons in a Shallow Sand Aquifer |
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| Authors: | JP Barker G C Patrick D Major |
| Institution: | 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 waters, and chemical and biological aspects of organic contaminant transport in ground waters. He is a member of the Institute for Groundwater Research at Waterloo.;Guy C. Patrick obtained his M.Sc. in hydrogeology at the University of Waterloo. His research addresses 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 employed as a hydrogeologist with Golder Associates (4104 148th Ave., N.E., Seattle, WA 98052).;David Major is completing his Ph.D. in the biology department, University of Waterloo (Waterloo, Ontario, Canada, N2L 3G1). His research addresses the biotransformation of monoaromatics in ground water systems and the methods for enhancing biotransformations as remedial means. He obtained his B.Sc. and his M.Sc. in biology from the University of Waterloo. |
| Abstract: | Inadvertent release of petroleum products such as gasoline into the subsurface can initiate ground water contamination, particularly by the toxic, water-soluble and mobile gasoline components: benzene, toluene and xylenes (BTX). This study was undertaken to examine the processes controlling the rate of movement and the persistence of dissolved BTX in ground water in a shallow, unconfined sand aquifer. Water containing about 7.6 mg/ L total BTX was introduced below the water table and the migration of contaminants through a sandy aquifer was monitored using a dense sampling network. BTX components migrated slightly slower than the ground water due to sorptive retardation. Essentially all the injected mass of BTX was lost within 434 days due to biodegradation. Rates of mass loss were similar for all monoaromatics; benzene was the only component to persist beyond 270 days. Laboratory biodegradation experiments produced similar rates, even when the initial BTX concentration varied. A dominant control over BTX biodegradation was the availability of dissolved oxygen. BTX persisted at the field site in layers low in dissolved oxygen. Decreasing mass loss rates over time observed in the field experiment are not likely due to first-order deeradation rates, but rather to the persistence of small fractions of BTX mass in anoxic layers. |
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