Christopher Mills
Science and Products
Geochemical Signatures of Covered Mineral Deposits in the Northern Midcontinent
We are evaluating the potential of geochemical prospecting techniques that have shown promise in other covered terranes for mineral exploration in the northern midcontinent of the U.S. Novel components will be added to these methods with the objective of method advancement and improving our understanding of processes controlling the transmission of unique geochemical signatures from buried...
Geochemical Signatures and Environmental Impacts of Ore and Trace Mineralization in the Southern Midcontinent
The overall project objective is a comprehensive analysis of the natural and anthropogenic consequences of extensive ore and trace mineralization in the southern midcontinent of the U.S. with a focus on Missouri. This will be conducted at two scales: 1) landscape and 2) process-level.
1) Landscape scale using geospatial and machine learning techniques to combine multiple geochemical and...
The Pothole Hydrology-Linked Systems Simulator (PHyLiSS)—Development and application of a systems model for prairie-pothole wetlands
The North American Prairie Pothole Region covers about 770,000 square kilometers of the United States and Canada (including parts of 5 States and 3 provinces: North Dakota, South Dakota, Montana, Minnesota, Iowa, Saskatchewan, Manitoba, and Alberta). The Laurentide Ice Sheet shaped the landscape of the region about 12,000 to 14,000 years ago. The...
McKenna, Owen P.; Mushet, David M.; Scherff, Eric J.; Mclean, Kyle I.; Mills, Christopher T.
Modifications to EPA Method 3060A to Improve Extraction of Cr(VI) from Chromium Ore Processing Residue-Contaminated Soils
It has been shown that EPA Method 3060A does not adequately extract Cr(VI) from chromium ore processing residue (COPR). We modified various parameters of EPA 3060A toward understanding the transformation of COPR minerals in the alkaline extraction and improving extraction of Cr(VI) from NIST SRM 2701, a standard COPR-contaminated soil. Aluminum...
Mills, Christopher T.; Bern, Carleton R.; Wolf, Ruth E.; Foster, Andrea L.; Morrison, Jean M.; Benzel, William M. Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands
Inland waters are increasingly recognized as critical sites of methane emissions to the atmosphere, but the biogeochemical reactions driving such fluxes are less well understood. The Prairie Pothole Region (PPR) of North America is one of the largest wetland complexes in the world, containing millions of small, shallow wetlands. The sediment pore...
Martins, Paula; Hoyt, David W.; Bansal, Sheel; Mills, Christopher T.; Tfaily, Malak; Tangen, Brian A.; Finocchiaro, Raymond; Johnston, Michael D.; McAdams, Brandon C.; Solensky, Matthew J.; Smith, Garrett J.; Chin, Yu-Ping; Wilkins, Michael J. Changes in pond water levels and surface extent due to climate variability alter solute sources to closed-basin Prairie-Pothole wetland ponds, 1979 to 2012
Wetter conditions beginning in 1993 resulted in marked changes in water levels and surface extent of prairie-pothole region wetland ponds, including closed-basin wetlands in the Cottonwood Lake area of North Dakota, U.S.A. Pond water levels after 1993 were consistently 0.5 to 2 m higher than during 1979–1993 (≤ 1 m deep) in wetlands...
LaBaugh, James W.; Mushet, David M.; Rosenberry, Donald O.; Euliss, Ned H.; Goldhaber, Martin B.; Mills, Christopher T.; Nelson, Richard D. Controls on the geochemical evolution of Prairie Pothole Region lakes and wetlands over decadal time scales
One hundred sixty-seven Prairie Pothole lakes, ponds and wetlands (largely lakes) previously analyzed chemically during the late 1960’s and early to mid-1970’s were resampled and reanalyzed in 2011–2012. The two sampling periods differed climatically. The earlier sampling took place during normal to slightly dry conditions, whereas the latter...
Goldhaber, Martin B.; Mills, Christopher T.; Mushet, David M.; McCleskey, R. Blaine; Rover, Jennifer The use of amino acid indices for assessing organic matter quality and microbial abundance in deep-sea Antarctic sediments of IODP Expedition 318
The Adélie Basin, located offshore of the Wilkes Land margin, experiences unusually high sedimentation rates (~ 2 cm yr− 1) for the Antarctic coast. This study sought to compare depthwise changes in organic matter (OM) quantity and quality with changes in microbial biomass with depth at this high-deposition site and an offshore...
Carr, Stephanie A; Mills, Christopher T.; Mandernack, Kevin W 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...
Manning, Andrew H.; Mills, Christopher T.; Morrison, Jean M.; Ball, Lyndsay B.
Chemical and biotic characteristics of prairie lakes and large wetlands in south-central North Dakota—Effects of a changing climate
The climate of the prairie pothole region of North America is known for variability that results in significant interannual changes in water depths and volumes of prairie lakes and wetlands; however, beginning in July 1993, the climate of the region shifted to an extended period of increased precipitation that has likely been unequaled in the...
Mushet, David M.; Goldhaber, Martin B.; Mills, Christopher T.; McLean, Kyle I.; Aparicio, Vanessa M.; McCleskey, R. Blaine; Holloway, JoAnn M.; Stockwell, Craig A. Weathering and transport of chromium and nickel from serpentinite in the Coast Range ophiolite to the Sacramento Valley, California, USA
A soil geochemical study in northern California was done to investigate the role that weathering and transport play in the regional distribution and mobility of geogenic Cr and Ni, which are both potentially toxic and carcinogenic. These elements are enriched in ultramafic rocks (primarily serpentinite) and the soils derived from them (1700–...
Morrison, Jean M.; Goldhaber, Martin B.; Mills, Christopher T.; Breit, George N.; Hooper, Robert L.; Holloway, JoAnn M.; Diehl, Sharon F.; Ranville, James F. 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...
Goldhaber, Martin B.; Mills, Christopher T.; Morrison, Jean M.; Stricker, Craig A.; Mushet, David M.; LaBaugh, James W. 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-...
Mills, Christopher T.; Slater, Gregory F.; Dias, Robert F.; Carr, Stephanie A.; Reddy, Christopher M.; Schmidt, Raleigh; Mandernack, Kevin W. 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...
Mills, Christopher T.; Goldhaber, Martin B.