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Natural Biological Attenuation of Benzene in Ground Water Beneath a Manufacturing Facility
Author(s) -
Davis John W.,
Klier Nancy J.,
Carpenter Constance L.
Publication year - 1994
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1994.tb00636.x
Subject(s) - aquifer , btex , groundwater , environmental chemistry , benzene , microcosm , biodegradation , vadose zone , environmental science , bioremediation , contamination , environmental engineering , soil science , soil water , chemistry , geology , geotechnical engineering , ecology , ethylbenzene , organic chemistry , biology
Subsurface unsaturated soils and ground water directly beneath a manufacturing site have been shown to contain benzene. The vadose zone appears to be the current source for benzene to the aquifer. Although the ground water contains several mg/1 of contamination in the area immediately beneath the source, benzene was not detected in monitoring wells approximately 400 feet downgradient. Based upon the length of time benzene has been present in the ground water, as well as the permeability of the aquifer, physical processes alone such as adsorption and advection/dispersion are unlikely to account for the observed attenuation. Results from this investigation indicated the attenuation was primarily due to the natural biological processes occurring within the aquifer. Evidence for the natural bioremediation of benzene from the ground water included: (1) analysis of ground‐water chemistry, (2) laboratory studies demonstrating benzene biodegradation in aquifer samples, and (3) computer simulations examining contaminant transport. Laboratory studies indicated that under conditions similar to those encountered in the ground water, benzene was degraded to carbon dioxide by the naturally occurring microorganisms. The aerobic degradation of benzene in aquifer samples was quite rapid, with the time for 50% disappearance of the parent compound ranging from 4 to 14 days. In situ analyses of the ground water indicated significant levels of dissolved oxygen throughout the aquifer. Thus, the availability of oxygen should not limit the aerobic biodegradation of benzene. However, benzene was also shown to degrade under anaerobic conditions in microcosms prepared with aquifer material. Computer model simulations were also conducted to examine the processes influencing the transport of benzene in the aquifer. Results from the model simulations indicated biodegradation was the dominant process influencing attenuation of the contaminant.