Publications

Applications of transport time scales are pervasive in biological, hydrologic, and geochemical studies yet these times scales are not consistently defined and applied with rigor in the literature. We compare three transport time scales (flushing time, age, and residence time) commonly used to measure the retention of water or scalar quantities transported with water. We identify the...

Hydrostratigraphic and geochemical data collected in two adjacent watersheds on the Delmarva Peninsula, in Kent County, Maryland, indicate that shallow subsurface stratigraphy is an important factor that affects the concentrations of nitrogen in ground water discharging as stream base flow. The flux of nitrogen from shallow aquifers can contribute substantially to the eutrophication of...

A recently described unicellular chlorophytic alga isolated from meromictic Mono Lake, California, occupies a niche that spans two environments: the upper oxic mixolimnion and the deeper anoxic and highly reducing monimolimnion. This organism, Picocystis sp. strain ML, accounts for nearly 25% of the primary production during the winter bloom and more than 50% at other times of the year...

Field and laboratory column experiments were performed to assess the effect of elevated pH and reduced ionic strength on the mobilization of natural colloids in a ferric oxyhydroxide-coated aquifer sediment. The field experiments were conducted as natural gradient injections of groundwater amended by sodium hydroxide additions. The laboratory experiments were conducted in columns of...

Adsorption, complexation, and dissolution reactions strongly influenced the transport of metal ions complexed with ethylenediaminetetraacetic acid (EDTA) in a predominantly quartz-sand aquifer during two tracer tests conducted under mildly reducing conditions at pH 5.8 to 6.1. In tracer test M89, EDTA complexes of zinc (Zn) and nickel (Ni), along with excess free EDTA, were injected such...

Dispersive transport of groundwater solutes was investigated as part of a multispecies reactive tracer test conducted under spatially variable chemical conditions in an unconfined, sewage‐contaminated sand and gravel aquifer on Cape Cod, Massachusetts. Transport of the nonreactive tracer bromide (Br) reflected physical and hydrologic processes. Transport of the reactive tracer nickel (Ni...

The binding of Hg(II) to dissolved organic matter (DOM; hydrophobic acids isolated from the Florida Everglades by XAD-8 resin) was measured at a wide range of Hg-to-DOM concentration ratios using an equilibrium dialysis ligand exchange method. Conditional distribution coefficients (KDOM‘) determined by this method were strongly affected by the Hg/DOM concentration ratio. At Hg/DOM ratios...

A two-dimensional numerical solute transport model was developed for simulating an enhanced in situ denitrification experiment performed in a nitrate-contaminated aquifer on Cape Cod, Massachusetts. In this experiment, formate (HCOO-) was injected for a period of 26 days into the carbon-limited aquifer to stimulate denitrification. Calibration of the vertical-profile site model was...

Parasites and pathogens can influence the survivorship, behavior, and very structure of their host species. For example, experimental studies have shown that trematode parasites can cause high frequencies of severe limb malformations in amphibians. In a broad-scale field survey covering parts of California, Oregon, Washington, Idaho, and Montana, we examined relationships between the...

Conventional drinking water treatment processes were evaluated under typical water treatment plant conditions to determine their effectiveness in the removal of seven common antibiotics: carbadox, sulfachlorpyridazine, sulfadimethoxine, sulfamerazine, sulfamethazine, sulfathiazole, and trimethoprim. Experiments were conducted using synthetic solutions prepared by spiking both distilled/...

Site‐specific numerical modeling of four sites in two arid alluvial basins within the Nevada Test Site employs a conceptual model of deep arid system hydrodynamics that includes vapor transport, the role of xeric vegetation, and long‐term surface boundary transients. Surface boundary sequences, spanning 110 kyr, that best reproduce measured chloride concentration and matric potential...

Mercury (total and methyl) was evaluated in snow samples collected near a major mercury emission source on the Idaho National Engineering and Environmental Laboratory (INEEL) insoutheastern Idaho and 160 km downwind in Teton Range in westernWyoming. The sampling was done to assess near-field (