Publications

We studied methylmercury (MeHg) and total mercury (HgT) in impounded and natural surface waters in northwestern Minnesota, in settings ranging from agricultural to undeveloped. In a recently constructed (1995) permanent-pool impoundment, MeHg levels typically increased from inflow to outflow during 1997; this trend broke down from late 1998 to early 1999. MeHg levels in the outflow reached seasona

Geochemical data were collected to investigate the effects of topography and focused recharge on the transport of agricultural chemicals to groundwater through sandy soils. The research was done at a topographically high (upland) site and a depressional (lowland) site within a corn field. Agricultural chemicals that move readily with water were most directly affected by focused recharge to the low

Time series of ground-water head at a mid-marsh site near North Inlet, South Carolina, USA can be classified into five types of forcing signatures based on the dominant water flux governing water-level dynamics during a given time interval. The fluxes that can be recognized are recharge by tides and rain, evapotranspiration (ET), seepage into the near surface soil from below, and seepage across th

Volatilization and subsequent biodegradation near the water Table make up a coupled natural attenuation pathway that results in significant mass loss of hydrocarbons. Rates of biodegradation and volatilization were documented twice 12 years apart at a crude-oil spill site near Bemidji, Minnesota. Biodegradation rates were determined by calibrating a gas transport model to O2, CO2, and CH4 gas-conc

Elemental Hg-Au amalgamation mining practices are used widely in many developing countries resulting in significant Hg contamination of surrounding ecosystems. We have measured total Hg and methyl-Hg concentrations in sediment and water collected from artisanal Au mines and these are the first Hg speciation data from such mines in Suriname. Total Hg and methyl-Hg contents in mine-waste sediment an

Mercury (total and methyl) was evaluated in snow samples collected near a major mercury emission source on the Idaho National Engineering and Environmental Laboratory (INEEL) insoutheastern Idaho and 160 km downwind in Teton Range in westernWyoming. The sampling was done to assess near-field (<12 km)deposition rates around the source, compare them to those measured in a relatively remote, pristine

Benthic algae were collected from 20 streams in the Western Lake Michigan Drainages by the U.S. Geological Survey in May and June of 1993 as part of the National Water-Quality Assessment program. These streams were selected to represent "benchmark" streams that were minimally affected by human activities, especially agriculture, for comparison to other streams in similar environmental settings. St

Optimal estimators are developed for computation of suspended-sediment concentrations in streams. The estimators are a function of parameters, computed by use of generalized least squares, which simultaneously account for effects of streamflow, seasonal variations in average sediment concentrations, a dynamic error component, and the uncertainty in concentration measurements. The parameters are us

 The relation offish community composition to riparian cover at two spatial scales was compared at 18 streams in the agricultural Minnesota River Basin. The two spatial scales were: (1) local riparian zone (a 200 meter wide buffer extending 2 to 3 kilometers upstream of the sampling reach); and (2) the upstream riparian zone (a 200 m wide buffer on the mainstem and all perennial tributaries upstre

Trace metal clean sampling and analysis techniques were used to examine the temporal patterns of Hg, Cu, and Zn concentrations in shallow ground water, and the relationships between metal concentrations in ground water and in a hydrologically connected river. Hg, Cu, and Zn concentrations in ground water ranged from 0.07 to 4.6 ng L−1, 0.07 to 3.10 μg L−1, and 0.17 to 2.18 μg L−1, respectively. Th

During spring 2001 there was much flooding in the Mississippi River Basin in Minnesota. Greater than normal precipitation starting with late fall rains in 2000, greater than normal snowfalls, a delayed snowmelt, and record rains in April, all contributed to the flooding. Parts of the southern one-half of Minnesota had streamflows of magnitudes not seen in more than 30 years. Approximately 50 count

The primary source of ground water for the city of Rochester, Olmsted County, southeastern Minnesota is the St. Peter-Prairie du Chien-Jordan aquifer. Based on results of a previous U.S. Geological Survey investigation in the Rochester area, relatively high rates of areal recharge to the St. Peter-Prairie du Chien-Jordan aquifer occur along the edge of the overlying Decorah-Platteville-Glenwood co