Christopher Mills
Christopher Mills is a Research Chemist with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 23
Insights into controls on hexavalent chromium in groundwater provided by environmental tracers, Sacramento Valley, California, USA
Environmental tracers are useful for determining groundwater age and recharge source, yet their application in studies of geogenic Cr(VI) in groundwater has been limited. Environmental tracer data from 166 wells located in the Sacramento Valley, northern California, were interpreted and compared to Cr concentrations to determine the origin and age of groundwater with elevated Cr(VI), and better u
Authors
Andrew H. Manning, Christopher T. Mills, Jean Morrison, Lyndsay B. Ball
Hydrogeochemistry of prairie pothole region wetlands: Role of long-term critical zone processes
This study addresses the geologic and hydrogeochemical processes operating at a range of scales within the prairie pothole region (PPR). The PPR is a 750,000 km2portion of north central North America that hosts millions of small wetlands known to be critical habitat for waterfowl and other wildlife. At a local scale, we characterized the geochemical evolution of the 92-ha Cottonwood Lake study are
Authors
Martin B. Goldhaber, Christopher T. Mills, Jean Morrison, Craig A. Stricker, David M. Mushet, James W. LaBaugh
The relative contribution of methanotrophs to microbial communities and carbon cycling in soil overlying a coal-bed methane seep
Seepage of coal-bed methane (CBM) through soils is a potential source of atmospheric CH4 and also a likely source of ancient (i.e. 14C-dead) carbon to soil microbial communities. Natural abundance 13C and 14C compositions of bacterial membrane phospholipid fatty acids (PLFAs) and soil gas CO2 and CH4 were used to assess the incorporation of CBM-derived carbon into methanotrophs and other members o
Authors
Christopher T. Mills, Gregory F. Slater, Robert F. Dias, Stephanie A. Carr, Christopher M. Reddy, Raleigh Schmidt, Kevin W. Mandernack
Laboratory investigations of the effects of nitrification-induced acidification on Cr cycling in vadose zone material partially derived from ultramafic rocks
Sacramento Valley (California, USA) soils and sediments have high concentrations of Cr(III) because they are partially derived from ultramafic material. Some Cr(III) is oxidized to more toxic and mobile Cr(VI) by soil Mn oxides. Valley soils typically have neutral to alkaline pH at which Cr(III) is highly immobile. Much of the valley is under cultivation and is both fertilized and irrigated. A ser
Authors
Christopher T. Mills, Martin B. Goldhaber
Using stable isotopes to understand hydrochemical processes in and around a Prairie Pothole wetland in the Northern Great Plains, USA
Millions of internally drained wetland systems in the Prairie Potholes region of the northern Great Plains (USA and Canada) provide indispensable habitat for waterfowl and a host of other ecosystem services. The hydrochemistry of these systems is complex and a crucial control on wetland function, flora and fauna. Wetland waters can have high concentrations of SO2-4 due to the oxidation of large am
Authors
Christopher T. Mills, Martin B. Goldhaber, Craig A. Stricker, JoAnn M. Holloway, Jean Morrison, Karl J. Ellefsen, Donald O. Rosenberry, Roland S. Thurston
The role of critical zone processes in the evolution of the Prairie Pothole Region wetlands
The Prairie Pothole Region, which occupies 900,000 km2 of the north central USA and south central Canada, is one of the most important ecosystems in North America. It is characterized by millions of small wetlands whose chemistry is highly variable over short distances. The study involved the geochemistry of surface sediments, wetland water, and groundwater in the Cottonwood Lakes area of North Da
Authors
Martin B. Goldhaber, Christopher T. Mills, Craig A. Stricker, Jean Morrison
Shoreline surveys of oil-impacted marsh in southern Louisiana, July to August 2010
This report describes shoreline surveys conducted in the marshes of Louisiana in areas impacted by oil spilled from the Deepwater Horizon offshore oil drilling platform in the Gulf of Mexico. Three field expeditions were conducted on July 7-10, August 12-14, and August 24-26, 2010, in central Barataria Bay and the Bird's Foot area at the terminus of the Mississippi River delta. This preliminary re
Authors
Raymond F. Kokaly, David Heckman, JoAnn Holloway, Sarai C. Piazza, Brady R. Couvillion, Gregory D. Steyer, Christopher T. Mills, Todd M. Hoefen
Carbon and nitrogen biogeochemistry of a Prairie Pothole Wetland, Stutsman County, North Dakota, USA
The concentration and form of dissolved organic C (DOC) and N species (NH4+ and NO3-) were investigated as part of a larger hydrogeochemical study of the Cottonwood Lake Study Area within the Prairie Potholes region. Groundwater, pore water and surface wetland water data were used to help characterize the relationships between surface and groundwater with respect to nutrient dynamics. Photosynthes
Authors
JoAnn M. Holloway, Martin B. Goldhaber, Christopher T. Mills
Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater
Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization’s maximum contaminant level for drinking water (50 μg L−1) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the southern Sacram
Authors
Christopher T. Mills, Jean Morrison, Martin B. Goldhaber, Karl J. Ellefsen
Microbial carbon cycling in oligotrophic regional aquifers near the Tono Uranium Mine, Japan as inferred from δ13C and Δ14C values of in situ phospholipid fatty acids and carbon sources
Microorganisms are ubiquitous in deep subsurface environments, but their role in the global carbon cycle is not well-understood. The natural abundance δ13C and Δ14C values of microbial membrane phospholipid fatty acids (PLFAs) were measured and used to assess the carbon sources of bacteria in sedimentary and granitic groundwaters sampled from three boreholes in the vicinity of the Tono Uranium Min
Authors
Christopher T. Mills, Yuki Amano, Gregory F. Slater, Robert F. Dias, Teruki Iwatsuki, Kevin W. Mandernack
The δ15N and δ18O values of N2O produced during the co-oxidation of ammonia by methanotrophic bacteria
In order to determine if the δ15N and δ18O values of N2O produced during co-oxidation of NH4+ by methanotrophic (methane oxidizing) bacteria can be isotopically distinguished from N2O produced either by autotrophic nitrifying or denitrifying bacteria, we conducted laboratory incubation experiments with pure cultures of methanotrophic bacteria that were provided NH4Cl as an oxidation substrate. The
Authors
Kevin W. Mandernack, Christopher T. Mills, Craig A. Johnson, Thomas Rahn, Chad Kinney
Science and Products
Filter Total Items: 23
Insights into controls on hexavalent chromium in groundwater provided by environmental tracers, Sacramento Valley, California, USA
Environmental tracers are useful for determining groundwater age and recharge source, yet their application in studies of geogenic Cr(VI) in groundwater has been limited. Environmental tracer data from 166 wells located in the Sacramento Valley, northern California, were interpreted and compared to Cr concentrations to determine the origin and age of groundwater with elevated Cr(VI), and better u
Authors
Andrew H. Manning, Christopher T. Mills, Jean Morrison, Lyndsay B. Ball
Hydrogeochemistry of prairie pothole region wetlands: Role of long-term critical zone processes
This study addresses the geologic and hydrogeochemical processes operating at a range of scales within the prairie pothole region (PPR). The PPR is a 750,000 km2portion of north central North America that hosts millions of small wetlands known to be critical habitat for waterfowl and other wildlife. At a local scale, we characterized the geochemical evolution of the 92-ha Cottonwood Lake study are
Authors
Martin B. Goldhaber, Christopher T. Mills, Jean Morrison, Craig A. Stricker, David M. Mushet, James W. LaBaugh
The relative contribution of methanotrophs to microbial communities and carbon cycling in soil overlying a coal-bed methane seep
Seepage of coal-bed methane (CBM) through soils is a potential source of atmospheric CH4 and also a likely source of ancient (i.e. 14C-dead) carbon to soil microbial communities. Natural abundance 13C and 14C compositions of bacterial membrane phospholipid fatty acids (PLFAs) and soil gas CO2 and CH4 were used to assess the incorporation of CBM-derived carbon into methanotrophs and other members o
Authors
Christopher T. Mills, Gregory F. Slater, Robert F. Dias, Stephanie A. Carr, Christopher M. Reddy, Raleigh Schmidt, Kevin W. Mandernack
Laboratory investigations of the effects of nitrification-induced acidification on Cr cycling in vadose zone material partially derived from ultramafic rocks
Sacramento Valley (California, USA) soils and sediments have high concentrations of Cr(III) because they are partially derived from ultramafic material. Some Cr(III) is oxidized to more toxic and mobile Cr(VI) by soil Mn oxides. Valley soils typically have neutral to alkaline pH at which Cr(III) is highly immobile. Much of the valley is under cultivation and is both fertilized and irrigated. A ser
Authors
Christopher T. Mills, Martin B. Goldhaber
Using stable isotopes to understand hydrochemical processes in and around a Prairie Pothole wetland in the Northern Great Plains, USA
Millions of internally drained wetland systems in the Prairie Potholes region of the northern Great Plains (USA and Canada) provide indispensable habitat for waterfowl and a host of other ecosystem services. The hydrochemistry of these systems is complex and a crucial control on wetland function, flora and fauna. Wetland waters can have high concentrations of SO2-4 due to the oxidation of large am
Authors
Christopher T. Mills, Martin B. Goldhaber, Craig A. Stricker, JoAnn M. Holloway, Jean Morrison, Karl J. Ellefsen, Donald O. Rosenberry, Roland S. Thurston
The role of critical zone processes in the evolution of the Prairie Pothole Region wetlands
The Prairie Pothole Region, which occupies 900,000 km2 of the north central USA and south central Canada, is one of the most important ecosystems in North America. It is characterized by millions of small wetlands whose chemistry is highly variable over short distances. The study involved the geochemistry of surface sediments, wetland water, and groundwater in the Cottonwood Lakes area of North Da
Authors
Martin B. Goldhaber, Christopher T. Mills, Craig A. Stricker, Jean Morrison
Shoreline surveys of oil-impacted marsh in southern Louisiana, July to August 2010
This report describes shoreline surveys conducted in the marshes of Louisiana in areas impacted by oil spilled from the Deepwater Horizon offshore oil drilling platform in the Gulf of Mexico. Three field expeditions were conducted on July 7-10, August 12-14, and August 24-26, 2010, in central Barataria Bay and the Bird's Foot area at the terminus of the Mississippi River delta. This preliminary re
Authors
Raymond F. Kokaly, David Heckman, JoAnn Holloway, Sarai C. Piazza, Brady R. Couvillion, Gregory D. Steyer, Christopher T. Mills, Todd M. Hoefen
Carbon and nitrogen biogeochemistry of a Prairie Pothole Wetland, Stutsman County, North Dakota, USA
The concentration and form of dissolved organic C (DOC) and N species (NH4+ and NO3-) were investigated as part of a larger hydrogeochemical study of the Cottonwood Lake Study Area within the Prairie Potholes region. Groundwater, pore water and surface wetland water data were used to help characterize the relationships between surface and groundwater with respect to nutrient dynamics. Photosynthes
Authors
JoAnn M. Holloway, Martin B. Goldhaber, Christopher T. Mills
Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater
Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization’s maximum contaminant level for drinking water (50 μg L−1) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the southern Sacram
Authors
Christopher T. Mills, Jean Morrison, Martin B. Goldhaber, Karl J. Ellefsen
Microbial carbon cycling in oligotrophic regional aquifers near the Tono Uranium Mine, Japan as inferred from δ13C and Δ14C values of in situ phospholipid fatty acids and carbon sources
Microorganisms are ubiquitous in deep subsurface environments, but their role in the global carbon cycle is not well-understood. The natural abundance δ13C and Δ14C values of microbial membrane phospholipid fatty acids (PLFAs) were measured and used to assess the carbon sources of bacteria in sedimentary and granitic groundwaters sampled from three boreholes in the vicinity of the Tono Uranium Min
Authors
Christopher T. Mills, Yuki Amano, Gregory F. Slater, Robert F. Dias, Teruki Iwatsuki, Kevin W. Mandernack
The δ15N and δ18O values of N2O produced during the co-oxidation of ammonia by methanotrophic bacteria
In order to determine if the δ15N and δ18O values of N2O produced during co-oxidation of NH4+ by methanotrophic (methane oxidizing) bacteria can be isotopically distinguished from N2O produced either by autotrophic nitrifying or denitrifying bacteria, we conducted laboratory incubation experiments with pure cultures of methanotrophic bacteria that were provided NH4Cl as an oxidation substrate. The
Authors
Kevin W. Mandernack, Christopher T. Mills, Craig A. Johnson, Thomas Rahn, Chad Kinney