Publications

A wireline-operated packer was designed for use with a standard geophysical logging system. The packer probe consists of a downhole packer inflated with water removed from the borehole by an in-line submersible pump, and a differential pressure transducer calibrated to measure the hydraulic-head difference between the zones above and below the packer. Analysis of the packer data is based...

No abstract available.

No abstract available.

Although it is well-known that concentrations of anthropogenic radionuclides and organochlorine compounds in aquatic systems have decreased since their widespread release has stopped in the United States, the magnitude and variability of rates of decrease are not well-known. Paleolimnological studies of reservoirs provide a tool for evaluating these long-term trends in riverine systems...

A mathematical model is developed to interpret the early-time recovering water level following the termination of pumping in wells subject to turbulent head losses. The model assumes that turbulent head losses dissipate immediately when pumping ends. In wells subject to both borehole storage and turbulent head losses, the early-time recovery exhibits a slope equal to 1/2 on log-log plots...

Under some conditions, a first-order kinetic model is a poor representation of biodegradation in contaminated aquifers. Although it is well known that the assumption of first-order kinetics is valid only when substrate concentration, S, is much less than the half-saturation constant, K(s), this assumption is often made without verification of this condition. We present a formal error...

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 several unresolved problems...

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 ∼ 0.5 nM) downgradient of the...

The potential for humic substances to serve as a terminal electron acceptor in microbial respiration and to function as an electron shuttle between Fe(III)‐reducing microorganisms and insoluble Fe(III) oxides was investigated. The Fe(III)‐reducing microorganism Geobacter metallireducens conserved energy to support growth from electron transport to humics as evidenced by continued...

As the result of a pipeline burst, a body of light aliphatic crude oil floats atop the groundwater in a shallow sand and gravel aquifer in a remote area outside Bemidji, Minnesota. Biodegradation has resulted in the formation of a plume of DOC downgradient from the oil body. Groundwater has also been contaminated in an area known as the spray zone, from vertical infiltration of DOC...

The objective of this study was to examine chemical changes in porewaters that occur over small scales (cm) as groundwater flows through the hyporheic zone and discharges to a stream in a temperate forest of northern Wisconsin. Hyporheic-zone porewaters were sampled at discrete depths of 2, 10, 15, 61, and 183 cm at three study sites in the study basin. Chemical profiles of dissolved...

The 1500 km Upper Mississippi River (UMR) consists of 29 navigation pools and can be divided into the upper reach (pools 1-4), the middle reach (pools 5-13), and the lower reach (pools 14-26). Comparison of composite bed sediment samples collected from the downstream third of 24 pools before and after the 1993 UMR flood provides fieldscale data on the effect of the flood on sediment...