Publications

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...

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...

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...

No abstract available.

A high concentration of dimethylsulfoniopropionate (DMSP) was found in the water column (0.1–1.8 µM particulate plus dissolved) of Mono Lake, CA, an alkaline, hypersaline waterbody. The dense Artemia monica population contained high levels of DMSP (1.7–2.5 mmol.g-1 wet weight), presumably as an osmolyte. Death of these brine shrimp caused accumulation of DMSP along the shoreline of the...

Environmental concern about brominated halocarbons like methyl bromide (MeBr) is focused on their potential to destroy stratospheric ozone. Photocatalysis of MeBr and other halocarbons in the stratosphere results in the liberation of reactive CI and Br atoms. Because Br atoms are perhaps as much as 100-fold more efficient at attacking ozone than are CI atoms, bromine’s lower abundance is...

No abstract available.

No abstract available.

This report identifies key technical issues related to hydrologic assessment of water flow in the unsaturated zone at low-level radioactive waste (LLW) disposal facilities. In addition, a methodology for incorporating these issues in the performance assessment of proposed LLW disposal facilities is identified and evaluated. The issues discussed fall into four areas:Estimating the water...

The effects of 10 sampling strategies on estimates of annual mean concentrations of the herbicides atrazine, alachlor, and cyanazine in selected midwestern rivers were tested. The accuracy of the strategies was computed by comparing time-weighted annual mean herbicide concentrations calculated from water samples collected from 17 locations on midwestern rivers, with simulated annual mean

The transport of many solutes in groundwater is dependent upon the relative rates of physical flow and microbial metabolism. Quantifying rates of microbial processes under subsurface conditions is difficult and is most commonly approximated using laboratory studies with aquifer materials. In this study, we measured in situ rates of denitrification in a nitrate-contaminated aquifer using...

An equilibrium-based solute transport model is developed for the simulation of trace metal fate and transport in streams. The model is formed by coupling a solute transport model with a chemical equilibrium submodel based on MINTEQ. The solute transport model considers the physical processes of advection, dispersion, lateral inflow, and transient storage, while the equilibrium submodel...