Peter B McMahon
Peter is a Research Hydrologist with the USGS Colorado Water Science Center in Lakewood, CO.
Pete McMahon’s current research interests include understanding the effects of hydrocarbon production activities on groundwater quality and identifying natural and human processes that create regional- and national-scale patterns in the chemistry of groundwater. He uses geochemical, isotope, noble-gas, and groundwater-age tracers to understand the origin and fate of chemicals of concern in groundwater.
Education and Certifications
Ph.D., 1990, Geology, University of South Carolina at Columbia
M.A., 1984, Geology, University of Texas at Austin
B.S., 1981, Geology, University of Missouri at Columbia
Science and Products
Filter Total Items: 14
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Filter Total Items: 116
Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater
Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in t
Authors
Francis H. Chapelle, Paul M. Bradley, Peter B. McMahon, Karl Kaiser, Ron Benner
Evolution of redox processes in groundwater
No abstract available.
Authors
Peter B. McMahon, Francis H. Chapelle, Paul M. Bradley
Use of diverse geochemical data sets to determine sources and sinks of nitrate and methane in groundwater, Garfield County, Colorado, 2009
Previous water-quality assessments reported elevated concentrations of nitrate and methane in water from domestic wells screened in shallow zones of the Wasatch Formation, Garfield County, Colorado. In 2009, the U.S. Geological Survey, in cooperation with the Colorado Department of Public Health and Environment, analyzed samples collected from 26 domestic wells for a diverse set of geochemical tra
Authors
P. B. McMahon, J.C. Thomas, A.G. Hunt
A comparison of recharge rates in aquifers of the United States based on groundwater-age data
An overview is presented of existing groundwater-age data and their implications for assessing rates and timescales of recharge in selected unconfined aquifer systems of the United States. Apparent age distributions in aquifers determined from chlorofluorocarbon, sulfur hexafluoride, tritium/helium-3, and radiocarbon measurements from 565 wells in 45 networks were used to calculate groundwater rec
Authors
P. B. McMahon, Niel Plummer, J.K. Böhlke, S.D. Shapiro, S.R. Hinkle
Use of geochemical, isotopic, and age tracer data to develop models of groundwater flow for the purpose of water management, northern High Plains aquifer, USA
A prolonged drought in the High Plains of Nebraska prompted the use of groundwater for cooling at the largest coal-fired power plant in the State. Prior to the drought, groundwater was used primarily for irrigation and the power plant relied exclusively on surface water stored in a nearby reservoir for cooling. Seepage from the reservoir system during the past ∼75 a has resulted in the buildup of
Authors
Peter B. McMahon, C. P. Carney, E. P. Poeter, Steven M. Peterson
Redox Conditions in Selected Principal Aquifers of the United States
Reduction/oxidation (redox) processes affect the quality of groundwater in all aquifer systems. Redox processes can alternately mobilize or immobilize potentially toxic metals associated with naturally occurring aquifer materials, contribute to the degradation or preservation of anthropogenic contami-nants, and generate undesirable byproducts, such as dissolved manganese (Mn2+), ferrous iron (Fe2+
Authors
P. B. McMahon, T.K. Cowdery, F. H. Chapelle, B.C. Jurgens
Water Quality in the High Plains Aquifer, Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming, 1999-2004
This report contains the major findings of a 1999-2004 assessment of water quality in the High Plains aquifer. It is one of a series of reports by the National Water-Quality Assessment (NAWQA) Program that present major findings for principal and other aquifers and major river basins across the Nation. In these reports, water quality is discussed in terms of local, regional, State, and national is
Authors
Jason J. Gurdak, Peter B. McMahon, Kevin Dennehy, Sharon L. Qi
An Excel Workbook for Identifying Redox Processes in Ground Water
The reduction/oxidation (redox) condition of ground water affects the concentration, transport, and fate of many anthropogenic and natural contaminants. The redox state of a ground-water sample is defined by the dominant type of reduction/oxidation reaction, or redox process, occurring in the sample, as inferred from water-quality data. However, because of the difficulty in defining and applying a
Authors
Bryant C. Jurgens, Peter B. McMahon, Francis H. Chapelle, Sandra M. Eberts
What does "water quality" mean?
No abstract available.
Authors
Francis H. Chapelle, Paul M. Bradley, Peter B. McMahon, Bruce Lindsey
Biodegradation of 17β-estradiol, estrone and testosterone in stream sediments
Biodegradation of 17β-estradiol (E2), estrone (E1), and testosterone (T) was investigated in three wastewater treatment plant (WWTP) affected streams in the United States. Relative differences in the mineralization of [4-14C] substrates were assessed in oxic microcosms containing saturated sediment or water-only from locations upstream and downstream of the WWTP outfall in each system. Upstream se
Authors
Paul M. Bradley, Larry B. Barber, Francis H. Chapelle, James L. Gray, Dana W. Kolpin, Peter B. McMahon
Biodegradation of 17β-estradiol, estrone, and testosterone in stream sediments
The release of endocrine-disrupting chemicals (EDCs) in wastewater treatment plant (WWTP) effluent poses a significant threat to the ecology of surface water receptors, due to impacts on the hormonal control, sexual development, reproductive success and community structure of the indigenous aquatic organisms and associated wildlife. Among the EDCs commonly observed in WWTP effluent, the natural [e
Authors
P. M. Bradley, F. H. Chapelle, L. B. Barber, P. B. McMahon, J.L. Gray, D.W. Kolpin
Distinguishing iron-reducing from sulfate-reducing conditions
Ground water systems dominated by iron‐ or sulfate‐reducing conditions may be distinguished by observing concentrations of dissolved iron (Fe2+) and sulfide (sum of H2S, HS−, and S= species and denoted here as “H2S”). This approach is based on the observation that concentrations of Fe2+ and H2S in ground water systems tend to be inversely related according to a hyperbolic function. That is, when F
Authors
F. H. Chapelle, P. M. Bradley, M.A. Thomas, P. B. McMahon
Science and Products
Filter Total Items: 14
No Result Found
Filter Total Items: 116
Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater
Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in t
Authors
Francis H. Chapelle, Paul M. Bradley, Peter B. McMahon, Karl Kaiser, Ron Benner
Evolution of redox processes in groundwater
No abstract available.
Authors
Peter B. McMahon, Francis H. Chapelle, Paul M. Bradley
Use of diverse geochemical data sets to determine sources and sinks of nitrate and methane in groundwater, Garfield County, Colorado, 2009
Previous water-quality assessments reported elevated concentrations of nitrate and methane in water from domestic wells screened in shallow zones of the Wasatch Formation, Garfield County, Colorado. In 2009, the U.S. Geological Survey, in cooperation with the Colorado Department of Public Health and Environment, analyzed samples collected from 26 domestic wells for a diverse set of geochemical tra
Authors
P. B. McMahon, J.C. Thomas, A.G. Hunt
A comparison of recharge rates in aquifers of the United States based on groundwater-age data
An overview is presented of existing groundwater-age data and their implications for assessing rates and timescales of recharge in selected unconfined aquifer systems of the United States. Apparent age distributions in aquifers determined from chlorofluorocarbon, sulfur hexafluoride, tritium/helium-3, and radiocarbon measurements from 565 wells in 45 networks were used to calculate groundwater rec
Authors
P. B. McMahon, Niel Plummer, J.K. Böhlke, S.D. Shapiro, S.R. Hinkle
Use of geochemical, isotopic, and age tracer data to develop models of groundwater flow for the purpose of water management, northern High Plains aquifer, USA
A prolonged drought in the High Plains of Nebraska prompted the use of groundwater for cooling at the largest coal-fired power plant in the State. Prior to the drought, groundwater was used primarily for irrigation and the power plant relied exclusively on surface water stored in a nearby reservoir for cooling. Seepage from the reservoir system during the past ∼75 a has resulted in the buildup of
Authors
Peter B. McMahon, C. P. Carney, E. P. Poeter, Steven M. Peterson
Redox Conditions in Selected Principal Aquifers of the United States
Reduction/oxidation (redox) processes affect the quality of groundwater in all aquifer systems. Redox processes can alternately mobilize or immobilize potentially toxic metals associated with naturally occurring aquifer materials, contribute to the degradation or preservation of anthropogenic contami-nants, and generate undesirable byproducts, such as dissolved manganese (Mn2+), ferrous iron (Fe2+
Authors
P. B. McMahon, T.K. Cowdery, F. H. Chapelle, B.C. Jurgens
Water Quality in the High Plains Aquifer, Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming, 1999-2004
This report contains the major findings of a 1999-2004 assessment of water quality in the High Plains aquifer. It is one of a series of reports by the National Water-Quality Assessment (NAWQA) Program that present major findings for principal and other aquifers and major river basins across the Nation. In these reports, water quality is discussed in terms of local, regional, State, and national is
Authors
Jason J. Gurdak, Peter B. McMahon, Kevin Dennehy, Sharon L. Qi
An Excel Workbook for Identifying Redox Processes in Ground Water
The reduction/oxidation (redox) condition of ground water affects the concentration, transport, and fate of many anthropogenic and natural contaminants. The redox state of a ground-water sample is defined by the dominant type of reduction/oxidation reaction, or redox process, occurring in the sample, as inferred from water-quality data. However, because of the difficulty in defining and applying a
Authors
Bryant C. Jurgens, Peter B. McMahon, Francis H. Chapelle, Sandra M. Eberts
What does "water quality" mean?
No abstract available.
Authors
Francis H. Chapelle, Paul M. Bradley, Peter B. McMahon, Bruce Lindsey
Biodegradation of 17β-estradiol, estrone and testosterone in stream sediments
Biodegradation of 17β-estradiol (E2), estrone (E1), and testosterone (T) was investigated in three wastewater treatment plant (WWTP) affected streams in the United States. Relative differences in the mineralization of [4-14C] substrates were assessed in oxic microcosms containing saturated sediment or water-only from locations upstream and downstream of the WWTP outfall in each system. Upstream se
Authors
Paul M. Bradley, Larry B. Barber, Francis H. Chapelle, James L. Gray, Dana W. Kolpin, Peter B. McMahon
Biodegradation of 17β-estradiol, estrone, and testosterone in stream sediments
The release of endocrine-disrupting chemicals (EDCs) in wastewater treatment plant (WWTP) effluent poses a significant threat to the ecology of surface water receptors, due to impacts on the hormonal control, sexual development, reproductive success and community structure of the indigenous aquatic organisms and associated wildlife. Among the EDCs commonly observed in WWTP effluent, the natural [e
Authors
P. M. Bradley, F. H. Chapelle, L. B. Barber, P. B. McMahon, J.L. Gray, D.W. Kolpin
Distinguishing iron-reducing from sulfate-reducing conditions
Ground water systems dominated by iron‐ or sulfate‐reducing conditions may be distinguished by observing concentrations of dissolved iron (Fe2+) and sulfide (sum of H2S, HS−, and S= species and denoted here as “H2S”). This approach is based on the observation that concentrations of Fe2+ and H2S in ground water systems tend to be inversely related according to a hyperbolic function. That is, when F
Authors
F. H. Chapelle, P. M. Bradley, M.A. Thomas, P. B. McMahon