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E. Michael Godsy

Publications and source records attributed to E. Michael Godsy.

8 recordsLinked to original sources
USGS2010

Simulation of aerobic and anaerobic biodegradation processes at a crude oil spill site

A two-dimensional, multispecies reactive solute transport model with sequential aerobic and anaerobic degradation processes was developed and tested. The model was used to study the field-scale solute transport and degradation processes at the Bemidji, Minnesota, crude oil spill site. The simulations included the biodegradation of volatile and nonvolatile fractions of dissolved organic carbon by aerobic processes, manganese and iron reduction, and methanogenesis. Model parameter estimates were constrained by published Monod kinetic parameters, theoretical yield estimates, and field biomass measurements. Despite the considerable uncertainty in the model parameter estimates, results of simulations reproduced the general features of the observed groundwater plume and the measured bacterial concentrations. In the simulation, 46% of the total dissolved organic carbon (TDOC) introduced into the aquifer was degraded. Aerobic degradation accounted for 40% of the TDOC degraded. Anaerobic processes accounted for the remaining 60% of degradation of TDOC: 5% by Mn reduction, 19% by Fe reduction, and 36% by methanogenesis. Thus anaerobic processes account for more than half of the removal of DOC at this site.

Water Resources Research↗
USGS2005

Methanogenic biodegradation of creosote contaminants in natural and simulated ground-water ecosystems

Wastes from a wood preserving plant in Pensacola, Florida have contaminated the near‐surface sand‐and‐gravel aquifer with creosote‐derived compounds and pentachlorophenol. Contamination resulted from the discharge of plant waste waters to and subsequent seepage from unlined surface impoundments that were in direct hydraulic contact with the ground water. Two distinct phases resulted when the creosote and water mixed: a denser than water hydrocarbon phase that moved vertically downward, and an organic‐rich aqueous phase that moved laterally with the ground‐water flow. The aqueous phase is enriched in organic acids, phenolic compounds, single‐ and double‐ring nitrogen, sulfur, and oxygen containing compounds, and single‐ and double‐ring aromatic hydrocarbons. The ground water is devoid of dissolved O 2 , is 60–70% saturated with CH 4 and contains H 2 S. Field analyses document a greater decrease in concentration of organic fatty acids, benzoic acid, phenol, 2‐, 3‐, 4‐methylphenol, quinoline, isoquinoline, l(2H)‐quinolinone, and 2(lH)‐isoquinolinone during downgradient movement in the aquifer than could be explained by dilution and/or dispersion. Laboratory microcosm studies have shown that within the study region, this effect can be attributed to rnicrobial degradation to CH 4 and CO 2 . A small but active methanogenic population was found on sediment materials taken from highly contaminated parts of the aquifer.

Ground Water↗
USGS2004

Inhibition of acetoclastic methanogenesis in crude oil- and creosote-contaminated groundwater

Results from a series of studies of methanogenic processes in crude oil- and creosote-contaminated aquifers indicate that acetoclastic methanogenesis is inhibited near non-aqueous sources. At a crude oil-contaminated site, numbers of acetoclastic methanogens found close to crude oil were one hundred times fewer than those of hydrogen- and formate-utilizing methanogens. In laboratory toxicity assays, crude oil collected from the site inhibited methane production from acetate but not from formate or hydrogen. Toxicity assays with aqueous creosote extract completely inhibited acetate utilization over the range of tested dilutions but only mildly affected formate and hydrogen utilization. The combined results from the laboratory and field studies suggest that in methanogenic contaminated aquifers, inhibition of acetoclastic methanogenesis may lead to a buildup of acetate relative to dissolved organic carbon.

Florida, Minnesota↗
USGS1993

Modeling steady-state methanogenic degradation of phenols in groundwater

Field and microcosm observations of methanogenic phenolic compound degradation indicate that Monod kinetics governs the substrate disappearance but overestimates the observed biomass. In this paper we present modeling results from an ongoing multidisciplinary study of methanogenic biodegradation of phenolic compounds in a sand and gravel aquifer contaminated by chemicals and wastes used in wood treatment. Field disappearance rates of four phenols match those determined in batch microcosm studies previously performed by E.M. Godsy and coworkers. The degradation process appears to be at steady-state because even after a sustained influx over several decades, the contaminants still are disappearing in transport downgradient. The existence of a steady-state degradation profile of each substrate together with a low biomass density in the aquifer indicate that the bacteria population is exhibiting no net growth. This may be due to the oligotrophic nature of the biomass population in which utilization and growth are approximately independent of concentration for most of the concentration range. Thus a constant growth rate should exist over much of the contaminated area which may in turn be balanced by an unusually high decay or maintenance rate due to hostile conditions or predation.

Journal of Contaminant Hydrology↗
USGS1989

Transport and degradation of water-soluble creosote-derived compounds

Creosote is the most extensively used insecticide and industrial wood preservative today. It is estimated that there are more than 600 wood-preserving plants in the United States, and their collective use of creosote exceeds 4.5xl0 6 kg/yr (von Rumker et al ., 1975). Creosote is a complex mixture of more than 200 major individual organic compounds with differing molecular weights, polarities, and functionalities, along with dispersed solids and products of polymerization (Novotny et al ., 1981). The major classes of compounds previously identified in creosote show that it consists of ∼85% (w/w) polynuclear aromatic compounds (PAH), ∼12% phenolic compounds, and ∼3% heterocyclic nitrogen, sulfur, and oxygen containing compounds (NSO).

Book chapter↗