Christopher Mills
Science and Products
Development of USGS Geochemical Reference Materials
The project focus was the development of traditional and microanalytical reference materials that support USGS geochemical investigations. Development of new microanalytical reference materials allows USGS scientists and outside customers to examine a greater range of sample types while maintaining a high degree of data reliability.
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...
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...
Macro and Micro Analytical Methods Development
The Macro and Micro Analytical Methods Development Project (MMAMD) provides access to the expertise of highly experienced research scientists and state of the art analytical instrumentation to develop new and unique analytical capabilities to solve complex problems beyond routine analysis.
Using stream-side groundwater discharge for geochemical exploration in mountainous terrain
Groundwater chemistry has been predominantly used in geochemical exploration studies to identify mineralized targets concealed under transported cover in areas with gentle topography. Another potentially valuable ap-plication that has received little attention is using groundwater chemistry to identify deposits concealed within mountain ridges. A...
Manning, Andrew H.; Morrison, Jean M.; Wanty, Richard; Mills, Christopher T.
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. Using halogens (Cl, Br, I) to understand the hydrogeochemical evolution of drought-derived saline porewater beneath a prairie wetland
Numerous closed-basin prairie wetlands throughout the Prairie Pothole Region (PPR) of North America maintain moderate surface pond salinities (total dissolved solids [TDS] from 1 to 10 g L− 1) under semiarid climate by accumulation of gypsum and saline lenses of sulfate-rich porewater (TDS...
Levy, Zeno F.; Mills, Christopher T.; Lu, Zunli; Goldhaber, Martin B.; Rosenberry, Donald O.; Mushet, David M.; Lautz, Laura K.; Zhou, Xiaoli; Siegel, Donald I. 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; 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.