Introduction: Research Hydrologist/Ecologist with the South Atlantic Water Science Center focused on understanding environmental contaminant mixture exposures and real versus perceived effects to human and environmental health.
Paul is project lead, along with Kelly Smalling, of the Drinking-Water and Wastewater Infrastructure Integrated Science Team of the Ecosystems Mission, Environmental Health Program. His research focuses on human exposures to and potential effects of inorganic, organic, and microbial contaminant mixtures in drinking water at the point of use and on anthropogenic contaminant mixtures as ecosystem stressors.
Professional Experience
1988–present: Research Ecologist/Hydrologist, U.S. Geological Survey
Expertise:
• Contaminant mixtures
• Drinking water
• Water quality
• Environmental health
Education and Certifications
B.S., Applied Biology, Georgia Institute of Technology, Atlanta, Georgia
M.S., Applied Biology, Georgia Institute of Technology, Atlanta, Georgia
Ph.D., Physiological Ecology, University of South Carolina, Columbia, South Carolina
Science and Products
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Arsenate inhibition of denitrification in nitrate contaminated sediments
Short-term and chronic exposure effects of arsenic on sediment denitrification were evaluated. N2O production rates were determined for As-contaminated (chronic treatment) and uncontaminated (short-term treatment) sediments exposed to a range of As concentrations. The As-containing sediments, collected from an herbicide-contaminated shallow aquifer, exhibited significantly lower rates of denitrifi
Influence of Pb on microbial activity in Pb-contaminated soils
Investigations of the influence of Pb on soil microbial communities have focused on Pb concentrations of 1 g kg-’ or less (Barkay et al., 1985; Capone et al., 1983; Chang and Broadbent, 1981; Doelman and Haanstra, 1979; Trevors et al., 1985). However, a number of environments exist in which Pb concentrations exceed 1 g kg-’ dry soil (Davenport and Peryea, 1991; Davis et al., 1992; Bisessar, 1982).
Does lead affect microbial metabolism in aquifer sediments under different terminal electron accepting conditions?
In groundwater from a petroleum hydrocarbon-contaminated aquifer. Substantial accumulation of aliphatic organic acids occurred only in methanogenic microcosms, and only trace amounts of acetic acid were detected in sulfate-reducing microcosms. This pattern parallels field observations in which high organic acid concentrations were detected in methanogenic zones, but only low concentrations of acet
Carbon limitation of denitrification rates in an anaerobic groundwater system
Rates of potential denitrification were determined for anaerobic aquifer sediments collected at a site where groundwater NO3 concentrations ranged from 0.7 ??M to 8.6 mM. A significant relation (p = 0.046) was observed between denitrification rates and the in situ concentration of NO3, but NO3 concentration only accounted for approximately 34% (r2) of the variation in activity. The highly signific
Influence of environmental factors on denitrification in sediment contaminated with JP-4 jet fuel
In 1975, the loss of approximately 83,000 gallons of JP-4 grade jet fuel resulted in contamination of the shallow aquifer near North Charleston, South Carolina. To identify those factors likely to influence microbial activity under denitrifying conditions, we examined the fate of amended NO3, the effect of pH, NO3, and PO4 on denitrification, and the variability of denitrification in sediments col
Effect of salinity on the critical nitrogen concentration of Spartina alterniflora Loisel
Nitrogen was withheld from the salt marsh grass Spartina alterniflora Loisel., in order to determine the effect of salinity (sea salts) on critical tissue nitrogen concentrations (defined here as the minimum tissue concentration required to sustain biomass accumulation). The critical nitrogen concentration per kilogram dry weight of above-ground tissue increased non-linearly from a mean of 8.2 g k
Role of microbial processes in linking sandstone diagenesis with organic-rich clays
Shows that the processes of microbial organic-acid production (via fermentation) in clays and microbial organic-acid consumption (via sulfate reduction) in sands effectively link organic-rich clays to sandstone diagenesis in the Black Creek Formation of South Carolina. Diagenetic processes have resulted in the formation of 10 volume percent calcite cement, 0.1 volume percent authigenic pyrite, and
Aerobic biodegradation potential of subsurface microorganisms from a jet fuel-contaminated aquifer
In 1975, a leak of 83,000 gallons (314,189 liters) of jet fuel (JP-4) contaminated a shallow water-table aquifer near North Charleston, S.C. Laboratory experiments were conducted with contaminated sediments to assess the aerobic biodegradation potential of the in situ microbial community. Sediments were incubated with 14C-labeled organic compounds, and the evolution of 14CO2 was measured over time
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Arsenate inhibition of denitrification in nitrate contaminated sediments
Short-term and chronic exposure effects of arsenic on sediment denitrification were evaluated. N2O production rates were determined for As-contaminated (chronic treatment) and uncontaminated (short-term treatment) sediments exposed to a range of As concentrations. The As-containing sediments, collected from an herbicide-contaminated shallow aquifer, exhibited significantly lower rates of denitrifiInfluence of Pb on microbial activity in Pb-contaminated soils
Investigations of the influence of Pb on soil microbial communities have focused on Pb concentrations of 1 g kg-’ or less (Barkay et al., 1985; Capone et al., 1983; Chang and Broadbent, 1981; Doelman and Haanstra, 1979; Trevors et al., 1985). However, a number of environments exist in which Pb concentrations exceed 1 g kg-’ dry soil (Davenport and Peryea, 1991; Davis et al., 1992; Bisessar, 1982).Does lead affect microbial metabolism in aquifer sediments under different terminal electron accepting conditions?
In groundwater from a petroleum hydrocarbon-contaminated aquifer. Substantial accumulation of aliphatic organic acids occurred only in methanogenic microcosms, and only trace amounts of acetic acid were detected in sulfate-reducing microcosms. This pattern parallels field observations in which high organic acid concentrations were detected in methanogenic zones, but only low concentrations of acetCarbon limitation of denitrification rates in an anaerobic groundwater system
Rates of potential denitrification were determined for anaerobic aquifer sediments collected at a site where groundwater NO3 concentrations ranged from 0.7 ??M to 8.6 mM. A significant relation (p = 0.046) was observed between denitrification rates and the in situ concentration of NO3, but NO3 concentration only accounted for approximately 34% (r2) of the variation in activity. The highly significInfluence of environmental factors on denitrification in sediment contaminated with JP-4 jet fuel
In 1975, the loss of approximately 83,000 gallons of JP-4 grade jet fuel resulted in contamination of the shallow aquifer near North Charleston, South Carolina. To identify those factors likely to influence microbial activity under denitrifying conditions, we examined the fate of amended NO3, the effect of pH, NO3, and PO4 on denitrification, and the variability of denitrification in sediments colEffect of salinity on the critical nitrogen concentration of Spartina alterniflora Loisel
Nitrogen was withheld from the salt marsh grass Spartina alterniflora Loisel., in order to determine the effect of salinity (sea salts) on critical tissue nitrogen concentrations (defined here as the minimum tissue concentration required to sustain biomass accumulation). The critical nitrogen concentration per kilogram dry weight of above-ground tissue increased non-linearly from a mean of 8.2 g kRole of microbial processes in linking sandstone diagenesis with organic-rich clays
Shows that the processes of microbial organic-acid production (via fermentation) in clays and microbial organic-acid consumption (via sulfate reduction) in sands effectively link organic-rich clays to sandstone diagenesis in the Black Creek Formation of South Carolina. Diagenetic processes have resulted in the formation of 10 volume percent calcite cement, 0.1 volume percent authigenic pyrite, andAerobic biodegradation potential of subsurface microorganisms from a jet fuel-contaminated aquifer
In 1975, a leak of 83,000 gallons (314,189 liters) of jet fuel (JP-4) contaminated a shallow water-table aquifer near North Charleston, S.C. Laboratory experiments were conducted with contaminated sediments to assess the aerobic biodegradation potential of the in situ microbial community. Sediments were incubated with 14C-labeled organic compounds, and the evolution of 14CO2 was measured over time - News