Publications

Sediment age profiles reconstructed from a sequence of historical bathymetry changes are used to investigate the subsurface distribution of historical sediments in a subembayment of the San Francisco Estuary. Profiles are created in a grid-based GIS modeling program that stratifies historical deposition into temporal horizons. The model's reconstructions are supported by comparisons to...

Extrapolating results of laboratory bioassays to streams is difficult, because conditions such as temperature and dissolved metal concentrations can change substantially on diel time scales. Field bioassays conducted for 96 h in two mining‐affected streams compared the survival of hatchery‐raised, metal‐näive westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to dissolved (0...

We compared streamflow in basins under the combined impacts of an upland dam and groundwater pumping withdrawals, by examining streamflow in the presence and absence of each impact. As a qualitative analysis, inter-watershed streamflow comparisons were performed for several rivers flowing into the east side of the Central Valley, CA. Results suggest that, in the absence of upland dams...

The major ion chemistry of water from an 11.42-km reach of the Pajaro River, a losing stream in central coastal California, shows a consistent pattern of higher concentrations during the 2nd (dry) half of the water year. Most solutes are conserved during flow along the reach, but [NO3−] decreases by ~30% and is accompanied by net loss of channel discharge and extensive surface–subsurface...

Measurements of the concentrations of dichlorodifluoromethane (CFC-12), tritium (3H), and sulfur hexafluoride (SF6) in groundwater from basaltic aquifers in Jeju Island, Korea, demonstrate a terrigenic source of SF6. Using a lumped-parameter dispersion model, groundwater was identified as young water (

The biotic ligand model considers the biological and geochemical complexities that affect metal exposure. It relates toxicity to the fraction of physiological active sites impacted by reactive metal species. The biodynamic model is a complementary construct that predicts bioaccumulation and assumes that toxicity occurs when influx rates exceed rates of loss and detoxification. In this...

The objective of this research was to investigate the effect of charring on near infrared spectra of materials likely to be present in forest fires in order to determine the feasibility of determining charred carbon in soils. Four materials (cellulose, lignin, pine bark and pine wood) and char from these materials created by charring for various durations (1 to 168 h) and at various...

Nitrite is a central intermediate in the nitrogen cycle and can persist in significant concentrations in ocean waters, sediment pore waters, and terrestrial groundwaters. To fully interpret the effect of microbial processes on nitrate (NO3-), nitrite (NO2-), and nitrous oxide (N2O) cycling in these systems, the nitrite pool must be accessible to isotopic analysis. Furthermore, because...

Ninety eight pharmaceuticals and other organic compounds (POOCs) that were amended to samples of chlorinated drinking-water were extracted and analyzed 1, 3, 6, 8, and 10 days after amendment to determine whether the total chlorine residual reacted with the amended POOCs in drinking water in a time frame similar to the residence time of drinking water in a water distribution system...

Releases of NaCl-rich (>100 000 mg/L) water that is co-produced from petroleum wells can adversely affect the quality of ground and surface waters. To evaluate produced water impacts on lakes, rivers and streams, an assessment of the contamination potential must be attainable using reliable and cost-effective methods. This study examines the feasibility of using geographic information...

[1] Chemical conditions were perturbed in an aquifer with an ambient pH of 5.9 and wastewater-derived adsorbed zinc (Zn) and phosphate (P) contamination by injecting a pulse of amended groundwater. The injected groundwater had low concentrations of dissolved Zn and P, a pH value of 4.5 resulting from equilibration with carbon dioxide gas, and added potassium bromide (KBr). Downgradient...

Halite brine (saturation ranging from 45 to 80%) lies within glacial sediments that fill the Onondaga Trough, a bedrock valley deepened by Pleistocene glaciation near Syracuse, New York State, USA. The most concentrated brine occupies the northern end of the trough, about 10 km downgradient of the northern limit of halite beds in the Silurian Salina Group, the assumed source of salt. The...