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Methylmercury (MeHg) degradation was investigated along an eutrophication gradient in the Florida Everglades by quantifying 14CH4 and 14CO2 production after incubation of anaerobic sediments with [14C]MeHg. Degradation rate constants (k) were consistently ≤0.1 d-1 and decreased with sediment depth. Higher k values were observed when shorter incubation times and lower MeHg amendment levels were...

A culture-independent molecular phylogenetic approach was used to survey constituents of microbial communities associated with an aquifer contaminated with hydrocarbons (mainly jet fuel) and chlorinated solvents undergoing intrinsic bioremediation. Samples were obtained from three redox zones: methanogenic, methanogenic-sulfate reducing, and iron or sulfate reducing. Small-subunit rRNA genes were amplified directly...

Reservoirs are used to store water for public water supply, flood control, irrigation, recreation, hydropower, and wildlife habitat, but also often store undesirable substances such as herbicides. The outflow from 76 reservoirs in the midwestern USA, was sampled four times in 1992 and four times in 1993. At least one...

This article summarizes recent experiences in arsenic (As) quantification, preservation, and speciation developed during AWWA Research Foundation (AWWARF) and Water Industry Technical Action Fund (WITAF) projects. The goal of this article is to alert analysts and decision-makers to potential problems in As analysis and speciation, because there appear to be...

Preliminary studies of mercury (Hg) cycling in the Everglades revealed that dissolved gaseous mercury (DGM), total mercury (Hg(T)), and reactive mercury (Hg(R)) show reproducible, diel trends. Peak water-column DGM concentrations were observed on or about noon, with a 3 to 7 fold increase over night-time concentrations. Production of DGM appears...

Field investigations of the hydrodynamics and the resuspension and transport of particulate matter in a bottom boundary layer were carried out in South San Francisco Bay, California during March-April 1995. The GEOPROBE, an instrumented bottom tripod, and broad-band acousti Doppler current profilers were used in this investigation. The instrument assemblage...

When the Wisconsin glacier retreated about 10,000 years ago, it left innumerable depressions scattered throughout the northern Great Plains. These depressional wetlands, called prairie potholes, contain water for various lengths of time in most years (Kantrud et al. 1989). Their size, permanence, hydrology, water chemistry, plant associations, and invertebrate communities...

This digital geospatial data set consists of structure contours of the top of the Laramie-Fox Hills aquifer along the Front Range of Colorado. The U.S. Geological Survey developed this data set as part of a project described in the report, "Structure, Outcrop, and Subcrop of the Bedrock Aquifers Along...

This digital geospatial data set consists of outlines of the study area in the report "Structure, Outcrop, and Subcrop of the Bedrock Aquifers Along the Western Margin of the Denver Basin, Colorado" (Robson and others, 1998)....

Remediation goals for the source areas of a chlorinated ethene‐contaminated groundwater plume were identified by assessing the natural attenuation capacity of the aquifer system. The redox chemistry of the site indicates that sulfate‐reducing (H2 ∼ 2 nanomoles [nM]) per liter conditions near the contaminant source grade to Fe(III)‐reducing conditions (H2...

This digital geospatial data set consists of locations of coal, oil, gas and water wells shown as data points in the report, "Structure, Outcrop, and Subcrop of the Bedrock Aquifers Along the Western Margin of the Denver Basin, Colorado" (Robson and others, 1998)....

This digital geospatial data set consists of structure contours on the base of the upper member of the Arapahoe aquifer. The U.S. Geological Survey developed this data set as part of a project described in the report,"Structure, Outcrop, and Subcrop of the Bedrock Aquifers Along the Western Margin of the...

This chapter reviews a number of applications of isotopic techniques for the investigation of carbon cycling processes. Carbon dioxide (C02) is an important greenhouse gas. Its concentration in the atmosphere has increased from an estimated 270 ppm at the beginning of the industrial revolution to ∼ 360 ppm at present....

The entrapment zo as long been considered an important region of the San Francisco estuary. It has been the subject of several previous studies, and its location has been suggested as an index of condition of the estuarine ecosystem.A close correlate of this location, X2 1, is now used as...

No abstract available....

The closed chamber method was used to assess nitrous oxide (N2O) fluxes from corn (Zea mays, L.) fields during the 1995 growing season. The study area was characterized by a claypan soil overlying a nitrate (NO31-)-enriched glacial-drift aquifer. Denitrification produced N2O fluxes of 0.2-6.9 g ha-1 hr-1 early in the...

The bioaccumulation of trace elements in aquatic organisms can be described with a kinetic model that includes linear expressions for uptake and elimination from dissolved and dietary sources. Within this model, trace element trophic transfer is described by four parameters: the weight-specific ingestion rate (IR); the assimilation efficiency (AE); the...

Northern Thurston County is underlain by as much as 1,800 feet of unconsolidated deposits of Pleistocene Age that are of glacial and nonglacial origin. Iterpretation of approximately 1,140 drillers' logs led to the delineation of seven major geohydrologic units, four of which are significant aquifers. Precipitation ranges from about 35...

Water resources data for the 1997 water year for Massachusetts and Rhode Island consists of records of stage, discharge, and water quality of streams; contents of lakes and reservoirs; and ground-water levels. This report contains discharge records for 86 gaging stations, month end contents of 4 lakes and reservoirs, water...

The effects of pesticide application, hydrology, and chemical and physical properties on the occurrence of pesticides in surface water in the San Joaquin River Basin, California, were examined. The study of pesticide occurrence in the highly agricultural San Joaquin?Tulare Basins is part of the National Water-Quality Assessment Program of the...

This report presents all analytical determinations for samples collected from Yellowstone National Park and vicinity during 1974 and 1975. Water temperature, pH, Eh, and dissolved O2 were determined on-site. Total alkalinity and F were determined on the day of sample collection. Flame atomic-absorption spectrometry was used to determine concentrations of Li, Na, K,...

A cooperative project between the U.S. Geological Survey (USGS) and the Wisconsin Department of Natural Resources (DNR) was begun with the objectives of describing water quality and its relation to the hydrology of Wisconsin's principal aquifers and summarizing instances of ground-water contamination and quality problems from information available in DNR...

A five-sheet hydrologic investigations atlas provides flood-peak elevation data and delineates the areal extent of flooding of the Missouri, the Mississippi, and the Meramec Rivers and the River des Peres in St. Louis and vicinity from August 1 through 3, 1993. The August 1993 flood is compared with the Federal...