Publications

The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground‐water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understandi

Since 1982, the Iowa Groundwater Monitoring (IGWM) Program has been used to sample untreated groundwater from Iowa municipal wells for selected agricultural chemicals. This long-term database was used to determine if concentrations of select agricultural chemicals in groundwater have changed with time. Nitrate, alachlor [2-chloro-2′-6′-diethyl-N-(methoxymethyl)-acetanilide], atrazine (2-chloro-4-e

A new model quantities the effect of soil structure, considered as the arrangement of particles in the soil, on soil water retention. The model partitions the pore space into texture-related and structure-related components, the textural component being what can be deduced to exist if the arrangement of the particles were random, and the structural component being the remainder. An existing model,

Suspended sediment was isolated from water samples collected from the Mississippi River at Thebes, IL, eight times over a 5-year period from May 1988 through September 1993 in order to evaluate the transport of lipophilic halogenated organic compounds associated with the suspended sediment. Two hydrologic extremes were included-the 1988 drought and the 1993 flood. Halogenated organic compounds inc

Tracer experiments are valuable tools for analyzing the transport characteristics of streams and their interactions with shallow groundwater. The focus of this work is the design of tracer studies in high-gradient stream systems subject to advection, dispersion, groundwater inflow, and exchange between the active channel and zones in surface or subsurface water where flow is stagnant or slow movin

Since 1984, hydrologic data have been collected as part of a U.S. Geological Survey study of the occurrence and movement of acidic contamination in the aquifer and streams of the Pinal Creek drainage basin near Globe, Arizona. Ground-water data from that study are presented for water years 1994, 1995, and 1996 and include location, construction information, site plans, water levels, chemical and p

Natural surficial accumulations of nitrate-rich salts in the Atacama Desert, northern Chile, and in the Death Valley region of the Mojave Desert, southern California, are well known, but despite many geologic and geochemical studies, the origins of the nitrates have remained controversial. N and O isotopes in nitrate, and S isotopes in coexisting soluble sulfate, were measured to determine if some

The oxidation of methyl bromide (MeBr) in the water column of Mono Lake, CA, was studied by measuring the formation of H14CO3 from [14C]MeBr. Potential oxidation was detected throughout the water column, with highest rates occurring in the epilimnion (5-12 m depth). The oxidation of MeBr was eliminated by filter-sterilization, thereby demonstrating the involvement of bacteria. Vertical profiles of

Eukaryotic microorganisms (protists) are a very important component of microbial communities inhabiting groundwater aquifers This is not unexpected when one considers that many protists feed heterotrophically, by means of either phagotrophy (bacterivory) or osmotrophy. Protistan numbers are usually low (

To test the effects of sewage-derived organic matter on virus attachment, 32P-labeled bacteriophage PRD1, linear alkylbenzene sulfonates (LAS), and tracers were injected into sewage-contaminated (suboxic, elevated organic matter) and uncontaminated (oxic, low organic matter) zones of an iron oxide-coated quartz sand and gravel aquifer on Cape Cod, MA. In the uncontaminated zone, 83% of the PRD1 we

The clustering of orientations of hydraulically conductive fractures in bedrock at the Mirror Lake, New Hampshire fractured rock study site was investigated by comparing the orientations of fracture populations in two subvertical borehole arrays with those mapped on four adjacent subvertical roadcuts. In the boreholes and the roadcuts, the orientation of fracture populations appears very similar a

Modern day injection and recovery techniques designed to examine the transport behavior of microorganisms in groundwater have evolved from experiments conducted in the late 1800s, in which bacteria that form red or yellow pigments were used to trace flow paths through karst and fractured- rock aquifers. A number of subsequent groundwater hydrology studies employed bacteriophage that can be injecte