Peter B McMahon (Former Employee)
Science and Products
Filter Total Items: 14
No Result Found
Filter Total Items: 118
Occurrence of nitrous oxide in the central High Plains aquifer, 1999 Occurrence of nitrous oxide in the central High Plains aquifer, 1999
Nitrogen-enriched groundwater has been proposed as an important anthropogenic source of atmospheric nitrous oxide (N2O), yet few measurements of N2O in large aquifer systems have been made. Concentrations of N2O in water samples collected from the 124 000 km2 central High Plains aquifer in 1999 ranged from 1 to 940 nM, with a median concentration of 29 nM (n = 123). Eighty percent of the...
Authors
P.B. McMahon, B.W. Bruch, M.F. Becker, L. Pope, K.F. Dennehy
Hydraulic and geochemical performance of a permeable reactive barrier containing zero-valent iron, Denver Federal Center Hydraulic and geochemical performance of a permeable reactive barrier containing zero-valent iron, Denver Federal Center
The hydraulic and geochemical performance of a 366 m long permeable reactive barrier (PRB) at the Denver Federal Center, Denver, Colorado, was evaluated. The funnel and gate system, which was installed in 1996 to intercept and remediate ground water contaminated with chlorinated aliphatic hydrocarbons (CAHs), contained four 12.2 m wide gates filled with zero‐valent iron. Ground water...
Authors
P.B. McMahon, K.F. Dennehy, Mark Sandstrom
Denitrification in marine shales in northeastern Colorado Denitrification in marine shales in northeastern Colorado
Parts of the South Platte River alluvial aquifer in northeastern Colorado are underlain by the Pierre Shale, a marine deposit of Late Cretaceous age that is
Authors
Peter McMahon, J.K. Böhlke, Breton Bruce
N2O emissions from a nitrogen-enriched river N2O emissions from a nitrogen-enriched river
Nitrous oxide (N2O) emissions from the South Platte River in Colorado were measured using closed chambers in the fall, winter, and summer of 1994- 1995. The South Platte River was enriched in inorganic N (9-800 ??M) derived from municipal wastewater effluent and groundwater return flows from irrigated agricultural fields. River water was as much as 2500% supersaturated with N2O, and...
Authors
P.B. McMahon, K.F. Dennehy
Shallow ground-water quality of selected land-use/aquifer settings in the South Platte River basin, Colorado and Nebraska, 1993-95 Shallow ground-water quality of selected land-use/aquifer settings in the South Platte River basin, Colorado and Nebraska, 1993-95
No abstract available.
Authors
B. Bruce, P.B. McMahon
Nitrous oxide fluxes from a claypan soil overlying nitrate-enriched glacial drift Nitrous oxide fluxes from a claypan soil overlying nitrate-enriched glacial drift
The closed chamber method was used to assess nitrous oxide (N2O) fluxes from corn (Zea mays, L.) fields during the 1995 growing season. The study area was characterized by a claypan soil overlying a nitrate (NO31-)-enriched glacial-drift aquifer. Denitrification produced N2O fluxes of 0.2-6.9 g ha-1 hr-1 early in the growing season. Fluxes increased with increasing soil temperature, soil...
Authors
M.L. Pomes, D.H. Wilkison, P.B. McMahon
Water quality in the South Platte River basin, Colorado, Nebraska, and Wyoming, 1992-95 Water quality in the South Platte River basin, Colorado, Nebraska, and Wyoming, 1992-95
No abstract available.
Authors
Kevin Dennehy, David Litke, Cathy Tate, Sharon Qi, Peter McMahon, Breton Bruce, Robert Kimbrough, Janet Heiny
In-situ bioremediation of nitrate-contaminated ground water — A pilot test, Julesburg, Colorado, 1996–97 In-situ bioremediation of nitrate-contaminated ground water — A pilot test, Julesburg, Colorado, 1996–97
No abstract available.
Authors
P.B. McMahon, K.F. Dennehy, B. Bruce
Distribution of terminal electron-accepting processes in an aquifer having multiple contaminant sources Distribution of terminal electron-accepting processes in an aquifer having multiple contaminant sources
Concentrations of electron acceptors, electron donors, and H2 in groundwater were measured to determine the distribution of terminal electron-accepting processes (TEAPs) in an alluvial aquifer having multiple contaminant sources. Upgradient contaminant sources included two separate hydrocarbon point sources, one of which contained the fuel oxygenate methyl tertbutyl ether (MTBE)...
Authors
P.B. McMahon, B. Bruce
Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments
A study conducted in 1994 as part of the US Geological Survey's National Water-Quality Assessment Program, South Platte River Basin investigation, examined the effect of certain environmental factors on potential denitrification rates in nitrate-rich riverbed sediments. The acetylene block technique was used to measure nitrous oxide (N2O) production rates in laboratory incubations of...
Authors
K.S. Pfenning, P.B. McMahon
Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA
A survey of the chemical quality of ground water in the unconsolidated alluvial aquifer beneath a major urban center (Denver, Colorado, USA) was performed in 1993 with the objective of characterizing the quality of shallow ground-water in the urban area and relating water quality to land use. Thirty randomly selected alluvial wells were each sampled once for a broad range of dissolved...
Authors
B. Bruce, P.B. McMahon
Denitrification and mixing in a stream-aquifer system: Effects on nitrate loading to surface water Denitrification and mixing in a stream-aquifer system: Effects on nitrate loading to surface water
Ground water in terrace deposits of the South Platte River alluvial aquifer near Greeley, Colorado, USA, had a median nitrate concentration of 1857 μmol l−1. Median nitrate concentrations in ground water from adjacent floodplain deposits (468 μmol l−1) and riverbed sediments (461 μmol l−1), both of which are downgradient from the terrace deposits, were lower than the median concentration...
Authors
P.B. McMahon, J.K. Böhlke
Science and Products
Filter Total Items: 14
No Result Found
Filter Total Items: 118
Occurrence of nitrous oxide in the central High Plains aquifer, 1999 Occurrence of nitrous oxide in the central High Plains aquifer, 1999
Nitrogen-enriched groundwater has been proposed as an important anthropogenic source of atmospheric nitrous oxide (N2O), yet few measurements of N2O in large aquifer systems have been made. Concentrations of N2O in water samples collected from the 124 000 km2 central High Plains aquifer in 1999 ranged from 1 to 940 nM, with a median concentration of 29 nM (n = 123). Eighty percent of the...
Authors
P.B. McMahon, B.W. Bruch, M.F. Becker, L. Pope, K.F. Dennehy
Hydraulic and geochemical performance of a permeable reactive barrier containing zero-valent iron, Denver Federal Center Hydraulic and geochemical performance of a permeable reactive barrier containing zero-valent iron, Denver Federal Center
The hydraulic and geochemical performance of a 366 m long permeable reactive barrier (PRB) at the Denver Federal Center, Denver, Colorado, was evaluated. The funnel and gate system, which was installed in 1996 to intercept and remediate ground water contaminated with chlorinated aliphatic hydrocarbons (CAHs), contained four 12.2 m wide gates filled with zero‐valent iron. Ground water...
Authors
P.B. McMahon, K.F. Dennehy, Mark Sandstrom
Denitrification in marine shales in northeastern Colorado Denitrification in marine shales in northeastern Colorado
Parts of the South Platte River alluvial aquifer in northeastern Colorado are underlain by the Pierre Shale, a marine deposit of Late Cretaceous age that is
Authors
Peter McMahon, J.K. Böhlke, Breton Bruce
N2O emissions from a nitrogen-enriched river N2O emissions from a nitrogen-enriched river
Nitrous oxide (N2O) emissions from the South Platte River in Colorado were measured using closed chambers in the fall, winter, and summer of 1994- 1995. The South Platte River was enriched in inorganic N (9-800 ??M) derived from municipal wastewater effluent and groundwater return flows from irrigated agricultural fields. River water was as much as 2500% supersaturated with N2O, and...
Authors
P.B. McMahon, K.F. Dennehy
Shallow ground-water quality of selected land-use/aquifer settings in the South Platte River basin, Colorado and Nebraska, 1993-95 Shallow ground-water quality of selected land-use/aquifer settings in the South Platte River basin, Colorado and Nebraska, 1993-95
No abstract available.
Authors
B. Bruce, P.B. McMahon
Nitrous oxide fluxes from a claypan soil overlying nitrate-enriched glacial drift Nitrous oxide fluxes from a claypan soil overlying nitrate-enriched glacial drift
The closed chamber method was used to assess nitrous oxide (N2O) fluxes from corn (Zea mays, L.) fields during the 1995 growing season. The study area was characterized by a claypan soil overlying a nitrate (NO31-)-enriched glacial-drift aquifer. Denitrification produced N2O fluxes of 0.2-6.9 g ha-1 hr-1 early in the growing season. Fluxes increased with increasing soil temperature, soil...
Authors
M.L. Pomes, D.H. Wilkison, P.B. McMahon
Water quality in the South Platte River basin, Colorado, Nebraska, and Wyoming, 1992-95 Water quality in the South Platte River basin, Colorado, Nebraska, and Wyoming, 1992-95
No abstract available.
Authors
Kevin Dennehy, David Litke, Cathy Tate, Sharon Qi, Peter McMahon, Breton Bruce, Robert Kimbrough, Janet Heiny
In-situ bioremediation of nitrate-contaminated ground water — A pilot test, Julesburg, Colorado, 1996–97 In-situ bioremediation of nitrate-contaminated ground water — A pilot test, Julesburg, Colorado, 1996–97
No abstract available.
Authors
P.B. McMahon, K.F. Dennehy, B. Bruce
Distribution of terminal electron-accepting processes in an aquifer having multiple contaminant sources Distribution of terminal electron-accepting processes in an aquifer having multiple contaminant sources
Concentrations of electron acceptors, electron donors, and H2 in groundwater were measured to determine the distribution of terminal electron-accepting processes (TEAPs) in an alluvial aquifer having multiple contaminant sources. Upgradient contaminant sources included two separate hydrocarbon point sources, one of which contained the fuel oxygenate methyl tertbutyl ether (MTBE)...
Authors
P.B. McMahon, B. Bruce
Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments
A study conducted in 1994 as part of the US Geological Survey's National Water-Quality Assessment Program, South Platte River Basin investigation, examined the effect of certain environmental factors on potential denitrification rates in nitrate-rich riverbed sediments. The acetylene block technique was used to measure nitrous oxide (N2O) production rates in laboratory incubations of...
Authors
K.S. Pfenning, P.B. McMahon
Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA
A survey of the chemical quality of ground water in the unconsolidated alluvial aquifer beneath a major urban center (Denver, Colorado, USA) was performed in 1993 with the objective of characterizing the quality of shallow ground-water in the urban area and relating water quality to land use. Thirty randomly selected alluvial wells were each sampled once for a broad range of dissolved...
Authors
B. Bruce, P.B. McMahon
Denitrification and mixing in a stream-aquifer system: Effects on nitrate loading to surface water Denitrification and mixing in a stream-aquifer system: Effects on nitrate loading to surface water
Ground water in terrace deposits of the South Platte River alluvial aquifer near Greeley, Colorado, USA, had a median nitrate concentration of 1857 μmol l−1. Median nitrate concentrations in ground water from adjacent floodplain deposits (468 μmol l−1) and riverbed sediments (461 μmol l−1), both of which are downgradient from the terrace deposits, were lower than the median concentration...
Authors
P.B. McMahon, J.K. Böhlke