"Water, Microbes, and Rocks: the Geochemical Ecology of Contaminated Ground Water" 1997 Henry Darcy Distinguished Lecture
LIMITED OFFER - Now is the time to expand your ground water video library. Dr. Bennett's 1997 HDDL videotape is available at a discounted rate if purchased when you join AGWSE. Bennett's lecture is 45 minutes long and was professionally recorded and edited during his final presentation in September at the Las Vegas Convention Center. This is a limited time offer --see the membership application to order at the discounted rate that includes shipping and handling.
Phillip Bennett, Ph.D.
University of Texas at Austin
Annually the AGWSE Darcy Selection Committee recommends an outstanding ground water professional to be named the Henry Darcy Distinguished Lecture. The lecture series was initiated in 1987 to foster interest in ground water at the academic level. Since that time over 46,000 ground water students, faculty members and professionals across North America and Europe have heard the HDDL.
Bennett received a B.S. from The Evergreen State College, an M.S. in Environmental Science from the State University of New York, College of Environmental Science and Forestry, and a Ph.D. in Geology from Syracuse University. Since 1984 Dr. Bennett has been working at the U.S. Geological Survey's Bemidji research site as part of the multidisciplinary Toxic Substances Hydrology Program. His research project at The University of Texas includes silicate weathering kinetics, vadose-zone gas transport and chemistry, geochemical fate of high explosives, sediment transport in karst aquifers, reactive solute transport in fractures, and computational quantum-chemical descriptions of silicate surfaces.
ABSTRACT
When an organic substance, either natural or anthropogenic, infiltrates into an aquifer it becomes a component of a dynamic biogeochemical system. From the perspective of the subsurface microbe, these compounds may be benign, toxic or in most cases a rich source of carbon in an otherwise carbon-poor environment. Microbes consume this carbon, producing energy, cell mass, and geochemically reactive byproducts. The transformation of organic toxicants by native microorganisms, sometimes known as intrinsic bioremediation, is considered one of the most promising remediation approaches for contaminated ground water. From a geologic perspective, however, rapid metabolic transformation of organic substances also results in dramatic changes in the geochemical ecology of that aquifer, changing the native microbial consortia, aquifer mineralogy and permeability, vadose-zone gas composition, and water chemistry.
This lecture will examine the geology and geochemistry of microbial transformation of hydrocarbons using laboratory experiments, geochemical modeling, and field observations of contaminated aquifers, including results from the collaborative U. S. Geological Survey's Bemidji research program. Hydrocarbon degradation produces bicarbonate, acidity, and organic waste products, potentially changing the bulk geochemistry of the aquifer over wide areas, or more subtly, producing reactive micro-environments near attached microbes. How does oil degrade in ground water, what are the degradation byproducts, and what is the nature of the microenvironment created around an-attached microbe? Are these biogeochemical reactions a significant contribution to subsurface mineral diagenesis? Is mineral weathering enhanced only by surface colonizing microbes, or do microbes affect equilibria by altering 'bulk' pore-water chemistry? Do microbes colonize mineral surfaces in order to leach necessary nutrients, or is colonization controlled by surface charge and surface roughness? The goal of this lecture is to examine the geochemical consequences of subsurface microbial processes.
Bennett delivered his lecture at 39 academic sites in United States, Canada, Australia, England and Germany during the 1997 academic year.
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