Publications

Ground-water samples, core samples, and hydrologic measurements were obtained in the Central Oklahoma Aquifer as part of the pilot National Water-Quality Assessment Program. This report examines ground-water recharge and discharge, the potentiometric surface, the chemical and isotopic composition of ground water, and the abundances and textures of minerals in core materials to determine the rates

Movement of agricultural chemicals alachlor, atrazine, cyanazine, deethylatrazine, deisopropylatrazine, and metolachlor between surface water and ground water is documented by data collected from May 1989 through July 1991 at an unfarmed study site adjacent to the Cedar River in Iowa. During periods of runoff, these chemicals moved from the Cedar River into the alluvial aquifer with bank-storage w

The apparatus and methods used for the automatic, colorimetric determinations of dissolved nutrients (nitrate plus nitrite, nitrite, ammonium and orthophosphate) in natural waters are described. These techniques allow for the determination of nitrate plus nitrite for the concentration range 0.02 to 8 mg/L (milligrams per liter) as N (nitrogen); for nitrite, the range is 0.002 to 1.0 mg/L as N; for

No abstract available.

Suspended-solids concentration data were collected in San Francisco Bay during water year 1994. Optical backscatterance sensors and water samples were used to monitor suspended solids continuously at two sites in Suisun Bay, two sites in Central San Francisco Bay, and three sites in South San Francisco Bay. Sensors were positioned at two depths at each site. In addition, a shallow-water instrument

The upward flux of trichloroethene (TCE) vapor through the unsaturated zone above a contaminated, water-table aquifer at Picatinny Arsenal, New Jersey, has been studied under natural conditions over a 12-month period. Vertical gas-phase diffusion fluxes were estimated indirectly by measuring the TCE vapor concentration gradient in the unsaturated zone and using Fick's law to calculate the flux. Th

Measurements of oxidation-reduction potential (Eh) and concentrations of dissolved hydrogen (H2) were made in a shallow groundwater system contaminated with solvents and jet fuel to delineate the zonation of redox processes. Eh measurements ranged from +69 to -158 mV in a cross section of the contaminated plume and accurately delineated oxic from anoxic groundwater. Plotting measured Eh and pH val

Currently (1993), about 170 kg/yr of phosphorus discharges into Ashumet Pond on Cape Cod from a plume of sewage-contaminated ground water. Phosphorus in the plume is mobile in two distinct geochemical environments--an anoxic zone containing dissolved iron and a suboxic zone containing dissolved oxygen. Phosphorus mobility in the suboxic zone is due to saturation of available sorption sites. Phosph

No abstract available.

This study evaluates commonly used geostatistical methods to assess reproduction of hydraulic conductivity (K) structure and sensitivity under limiting amounts of data. Extensive conductivity measurements from the Cape Cod sand and gravel aquifer are used to evaluate two geostatistical estimation methods, conditional mean as an estimate and ordinary kriging, and two stochastic simulation methods,

Hydrological mechanisms controlling the variation of dissolved organic carbon (DOC) were investigated in the Deer Creek catchment located near Montezuma, CO. Patterns of DOC in streamflow suggested that increased flows through the upper soil horizon during snowmelt are responsible for flushing this DOC-enriched interstitial water to the streams. We examined possible hydrological mechanisms to expl

The recent identification of a novel sulfonated metabolite of alachlor in groundwater and metolachlor in soil is likely the result of glutathione conjugation. Glutathione conjugation is an important biochemical reaction that leads, in the case of alachlor, to the formation of a rather difficult to detect, water-soluble, and therefore highly mobile, sulfonated metabolite. Research from weed science