Publications

A modified version of the Hydrus software package that can directly or inversely simulate water flow in a transient centrifugal field is presented. The inverse solver for parameter estimation of the soil hydraulic parameters is then applied to multirotation transient flow experiments in a centrifuge. Using time‐variable water contents measured at a sequence of several rotation speeds...

As part of the Mercury Experiment to Assess Atmospheric Loadings in Canada and the United States (METAALICUS) the fate and transport of contemporary mercury (Hg) deposition in a boreal wetland was investigated using an experimentally applied stable mercury isotope. We applied high purity (99.2% ± 0.1) 202Hg(II) to a wetland plot to determine if (1) the 202Hg was detectable above the pool...

To test the effect of geochemical heterogeneity on microorganism transport in saturated porous media, we measured the removal of two microorganisms, the bacteriophage PRD1 and oocysts of the protozoan parasite Cryptosporidium parvum, in flow-through columns of quartz sand coated by different amounts of a ferric oxyhydroxide. The experiments were conducted over ranges of ferric...

As part of a multidisciplinary investigation designed to assess the implications of coal-bed methane development on water resources for the Powder River Basin of southeastern Montana, six wells were drilled through Paleocene-age coal bedsalong a 31-km east–west transect within the Tongue River drainage basin. Analysis of geophysical logs obtained in these wells provides insight into the

After reductive immobilization of uranium, the element may be oxidized and remobilized in the presence of nitrate by the activity of dissimilatory nitrate-reducing bacteria. We examined controls on microbially mediated nitrate-dependent U(IV) oxidation in landfill leachate-impacted subsurface sediments. Nitrate-dependent U(IV)-oxidizing bacteria were at least two orders of magnitude less...

Nitrate removal by hydrogen-coupled denitrification was examined using flow-through, packed-bed bioreactors to develop a small-scale, cost effective system for treating nitrate-contaminated drinking-water supplies. Nitrate removal was accomplished using a Rhodocyclus sp., strain HOD 5, isolated from a sole-source drinking-water aquifer. The autotrophic capacity of the purple non-sulfur

Stream salamanders are sensitive to acid mine drainage and may be sensitive to acidification and low acid neutralizing capacity (ANC) of a watershed. Streams in Shenandoah National Park, Virginia, are subject to episodic acidification from precipitation events. We surveyed 25 m by 2 m transects located on the stream bank adjacent to the water channel in Shenandoah National Park for...

Understanding transport of tritium (3H) in unsaturated zones is critical to evaluating options for waste isolation. Tritium typically is a large component of low-level radioactive waste (LLRW). Studies at the U.S. Geological Survey's Amargosa Desert Research Site (ADRS) in Nevada investigate 3H transport from a closed LLRW facility. Two boreholes are 100 and 160 m from the nearest waste...

Cinnabar (HgS) dissolution rates were measured in the presence of 12 different natural dissolved organic matter (DOM) isolates including humic, fulvic, and hydrophobic acid fractions. Initial dissolution rates varied by 1.3 orders of magnitude, from 2.31 × 10−13 to 7.16 × 10−12 mol Hg (mg C)−1 m−2s−1. Rates correlate positively with three DOM characteristics: specific ultraviolet...

The bacterial strains IMB-1T and CC495T, which are capable of growth on methyl chloride (CH3Cl, chloromethane) and methyl bromide (CH3Br, bromomethane), were isolated from agricultural soil in California fumigated with CH3Br, and woodland soil in Northern Ireland, respectively. Two pesticide-/herbicide-degrading bacteria, strains ER2 and C147, were isolated from agricultural soil in...

A solution containing 198Hg in the form of HgCl2 was added to a 4 m2 area of desert soils in Nevada, and soil Hg fluxes were measured using three dynamic flux chambers. There was an immediate release of 198Hg after it was applied, and then emissions decreased exponentially. Within the first 6 h after the isotope was added to the soil, ∼12 ng m-2 of 198Hg was emitted to the atmosphere...

This report is one in a series presenting results of an interdisciplinary U.S. Geological Survey (USGS) study of ground-water quality in the lower Red River watershed prior to open-pit and underground molybdenite mining at Molycorp's Questa mine. The stretch of the Red River watershed that extends from just upstream of the town of Red River to just above the town of Questa includes...