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
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Quantity and quality of ground-water discharge to the South Platte River, Denver to Fort Lupton, Colorado, August 1992 through July 1993
Water-quality studies conducted by the Metro Wastewater Reclamation District have indicated that during low flow in segments of the South Platte River between Denver and Fort Lupton, concentrations of dissolved oxygen are less than minimum concen- trations set by the State of Colorado. Low dissolved-oxygen concentrations are observed in two reaches of the river-they are about 3.3 to 6.4 miles and
Authors
P. B. McMahon, K.J. Lull, K. F. Dennehy, J.A. Collins
Some bacteria are beneficial!
Most people would agree that bacteria usually spell trouble where the quality of drinking water is con cerned. However, recent studies conducted by the U.S. Geological Survey (USGS) under the National Water-Quality Assessment (NAWQA) program have shown that some bacteria can improve the quality of water.
Authors
Peter B. McMahon
Effect of atrazine on potential denitrification in aquifer sediments
Agriculturaf use of fertilizers and herbicides has often resulted in nitrate and atrazine contamination of the shallow aquifers that underlay cultivated fields. In several cases, the concentrations of atrazine and nitrate dissolved in ground water are positively correlated (Spalding ef al., 1979; Chen and Druliner, 1987; Spalding et al., 1989). Because simultaneous application of nitrate fertilize
Authors
P. M. Bradley, F. H. Chapelle, M.L. Jagucki, P. B. McMahon
Atrazine mineralization potential of alluvial-aquifer sediments under aerobic conditions
No abstract available.
Authors
P. B. McMahon, F. H. Chapelle, M.L. Jagucki
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
Authors
P. B. McMahon, F. H. Chapelle, W. F. Falls, P. M. Bradley
Geochemistry of dissolved inorganic carbon in a Coastal Plain aquifer. 2. Modeling carbon sources, sinks, and δ13C evolution
Stable isotope data for dissolved inorganic carbon (DIC), carbonate shell material and cements, and microbial CO2 were combined with organic and inorganic chemical data from aquifer and confining-bed pore waters to construct geochemical reaction models along a flowpath in the Black Creek aquifer of South Carolina. Carbon-isotope fractionation between DIC and precipitating cements was treated as a
Authors
Peter B. McMahon, Francis H. Chapelle
Microbial production of organic acids in aquitard sediments and its role in aquifer geochemistry
MICROBIAL activity in aquifers plays an important part in the chemical evolution of ground water1-5. The most important terminal electron-accepting microbial processes in deeply buried anaerobic aquifers are iron reduction, sulphate reduction and methanogenesis5-8, each of which requires simple organic compounds or hydrogen (H2) as electron donors. Until now, the source of these compounds was unkn
Authors
P. B. McMahon, F. H. Chapelle
Geochemistry of dissolved inorganic carbon in a Coastal Plain aquifer. 1. Sulfate from confining beds as an oxidant in microbial CO2 production
A primary source of dissolved inorganic carbon (DIC) in the Black Creek aquifer of South Carolina is carbon dioxide produced by microbially mediated oxidation of sedimentary organic matter. Groundwater chemistry data indicate, however, that the available mass of inorganic electron acceptors (oxygen, Fe(III), and sulfate) and observed methane production is inadequate to account for observed CO2prod
Authors
F. H. Chapelle, P. B. McMahon
Streamflow, lake-flow patterns, rainfall, and quality of water and sediment in the vicinity of a hazardous-waste landfill near Pinewood, South Carolina, March 1987 through early January 1989
No abstract available.
Authors
R.A. Burt, P. B. McMahon, J. F. Robertson, D.D. Nagle
Geochemistry of dissolved inorganic carbon in a Coastal Plain aquifer. 2. Modeling carbon sources, sinks, and δ13C evolution
Stable isotope data for dissolved inorganic carbon (DIC), carbonate shell material and cements, and microbial CO2 were combined with organic and inorganic chemical data from aquifer and confining-bed pore waters to construct geochemical reaction models along a flowpath in the Black Creek aquifer of South Carolina. Carbon-isotope fractionation between DIC and precipitating cements was treated as a
Authors
Peter B. McMahon, Francis H. Chapelle
Reconnaissance hydrogeologic investigation of the Defense Waste Processing Facility and vicinity, Savannah River Plant, South Carolina
The hydrogeologic framework of the area around the Savannah River Plant, South Carolina consists of 2 to 3 separate water bearing units. In the northern half of the study area, the Barnwell and underlying McBean aquifers are considered one aquifer owing to the absence of the tan clay-confining unit between them. In the southern half of the study area they are separated by the tan clay into two aqu
Authors
K. F. Dennehy, D. C. Prowell, P. B. McMahon
Water movement in the unsaturated zone at a low-level radioactive-waste burial site near Barnwell, South Carolina
Four unsaturated-zone monitoring sites and a meteorologic station were installed at the low-level radioactive-waste burial site near Barnwell, S.C., to investigate the geohydrologic and climatologic factors affecting water movement in the unsaturated zone. The study site is located in the Atlantic Coastal Plain. The unsaturated zone consists of a few centimeters to more than 1 meter of surface san
Authors
Kevin F. Dennehy, Peter B. McMahon
Science and Products
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Filter Total Items: 14No Result Found
- Publications
Filter Total Items: 112
Quantity and quality of ground-water discharge to the South Platte River, Denver to Fort Lupton, Colorado, August 1992 through July 1993
Water-quality studies conducted by the Metro Wastewater Reclamation District have indicated that during low flow in segments of the South Platte River between Denver and Fort Lupton, concentrations of dissolved oxygen are less than minimum concen- trations set by the State of Colorado. Low dissolved-oxygen concentrations are observed in two reaches of the river-they are about 3.3 to 6.4 miles andAuthorsP. B. McMahon, K.J. Lull, K. F. Dennehy, J.A. CollinsSome bacteria are beneficial!
Most people would agree that bacteria usually spell trouble where the quality of drinking water is con cerned. However, recent studies conducted by the U.S. Geological Survey (USGS) under the National Water-Quality Assessment (NAWQA) program have shown that some bacteria can improve the quality of water.AuthorsPeter B. McMahonEffect of atrazine on potential denitrification in aquifer sediments
Agriculturaf use of fertilizers and herbicides has often resulted in nitrate and atrazine contamination of the shallow aquifers that underlay cultivated fields. In several cases, the concentrations of atrazine and nitrate dissolved in ground water are positively correlated (Spalding ef al., 1979; Chen and Druliner, 1987; Spalding et al., 1989). Because simultaneous application of nitrate fertilizeAuthorsP. M. Bradley, F. H. Chapelle, M.L. Jagucki, P. B. McMahonAtrazine mineralization potential of alluvial-aquifer sediments under aerobic conditions
No abstract available.AuthorsP. B. McMahon, F. H. Chapelle, M.L. JaguckiRole 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, andAuthorsP. B. McMahon, F. H. Chapelle, W. F. Falls, P. M. BradleyGeochemistry of dissolved inorganic carbon in a Coastal Plain aquifer. 2. Modeling carbon sources, sinks, and δ13C evolution
Stable isotope data for dissolved inorganic carbon (DIC), carbonate shell material and cements, and microbial CO2 were combined with organic and inorganic chemical data from aquifer and confining-bed pore waters to construct geochemical reaction models along a flowpath in the Black Creek aquifer of South Carolina. Carbon-isotope fractionation between DIC and precipitating cements was treated as aAuthorsPeter B. McMahon, Francis H. ChapelleMicrobial production of organic acids in aquitard sediments and its role in aquifer geochemistry
MICROBIAL activity in aquifers plays an important part in the chemical evolution of ground water1-5. The most important terminal electron-accepting microbial processes in deeply buried anaerobic aquifers are iron reduction, sulphate reduction and methanogenesis5-8, each of which requires simple organic compounds or hydrogen (H2) as electron donors. Until now, the source of these compounds was unknAuthorsP. B. McMahon, F. H. ChapelleGeochemistry of dissolved inorganic carbon in a Coastal Plain aquifer. 1. Sulfate from confining beds as an oxidant in microbial CO2 production
A primary source of dissolved inorganic carbon (DIC) in the Black Creek aquifer of South Carolina is carbon dioxide produced by microbially mediated oxidation of sedimentary organic matter. Groundwater chemistry data indicate, however, that the available mass of inorganic electron acceptors (oxygen, Fe(III), and sulfate) and observed methane production is inadequate to account for observed CO2prodAuthorsF. H. Chapelle, P. B. McMahonStreamflow, lake-flow patterns, rainfall, and quality of water and sediment in the vicinity of a hazardous-waste landfill near Pinewood, South Carolina, March 1987 through early January 1989
No abstract available.AuthorsR.A. Burt, P. B. McMahon, J. F. Robertson, D.D. NagleGeochemistry of dissolved inorganic carbon in a Coastal Plain aquifer. 2. Modeling carbon sources, sinks, and δ13C evolution
Stable isotope data for dissolved inorganic carbon (DIC), carbonate shell material and cements, and microbial CO2 were combined with organic and inorganic chemical data from aquifer and confining-bed pore waters to construct geochemical reaction models along a flowpath in the Black Creek aquifer of South Carolina. Carbon-isotope fractionation between DIC and precipitating cements was treated as aAuthorsPeter B. McMahon, Francis H. ChapelleReconnaissance hydrogeologic investigation of the Defense Waste Processing Facility and vicinity, Savannah River Plant, South Carolina
The hydrogeologic framework of the area around the Savannah River Plant, South Carolina consists of 2 to 3 separate water bearing units. In the northern half of the study area, the Barnwell and underlying McBean aquifers are considered one aquifer owing to the absence of the tan clay-confining unit between them. In the southern half of the study area they are separated by the tan clay into two aquAuthorsK. F. Dennehy, D. C. Prowell, P. B. McMahonWater movement in the unsaturated zone at a low-level radioactive-waste burial site near Barnwell, South Carolina
Four unsaturated-zone monitoring sites and a meteorologic station were installed at the low-level radioactive-waste burial site near Barnwell, S.C., to investigate the geohydrologic and climatologic factors affecting water movement in the unsaturated zone. The study site is located in the Atlantic Coastal Plain. The unsaturated zone consists of a few centimeters to more than 1 meter of surface sanAuthorsKevin F. Dennehy, Peter B. McMahon - News