Publications
Dive into our publications and explore the science from the Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology).
Filter Total Items: 3787
Dissolved sulfides in the oxic water column of San Francisco Bay, California
Trace contaminants enter major estuaries such as San Francisco Bay from a variety of point and nonpoint sources and may then be repartitioned between solid and aqueous phases or altered in chemical speciation. Chemical speciation affects the bioavailability of metals as well as organic ligands to planktonic and benthic organisms, and the partitioning of these solutes between phases. Our previous,
Authors
J.S. Kuwabara, G.W. Luther
Trace metals (Cd, Cu, Ni, and Zn) and nutrients in coastal waters adjacent to San Francisco Bay, California
Samples collected in December 1990 and July 1991 show that dissolved Cd, Cu, Ni, and Zn distributions in the Gulf of the Farallones are dominated by mixing of two end-members: (1) metal-enriched San Francisco Bay water and (2) offshore California Current water. The range of dissolved metal concentrations observed is 0.2–0.9 nmol kg−1 for Cd, 1–20 nmol kg−1 for Cu, 4–16 nmol kg−1 for Ni, and 0.2–20
Authors
A. VanGeen, Samuel N. Luoma
Computation of type curves for flow to partially penetrating wells in water-table aquifers
Evaluation of Neuman's analytical solution for flow to a well in a homogeneous, anisotropic, water-table aquifer commonly requires large amounts of computation time and can produce inaccurate results for selected combinations of parameters. Large computation times occur because the integrand of a semi-infinite integral involves the summation of an infinite series. Each term of the series requires
Authors
Allen F. Moench
Trace contaminants and nutrients in estuaries: The importance of process interdependence
No abstract available.
Authors
J.S. Kuwabara, J.E. Baker
Distributions of pesticides and organic contaminants between water and suspended sediment, San Francisco Bay, California
Suspended-sediment and water samples were collected from San Francisco Bay in 1991 during low river discharge and after spring rains. All samples were analyzed for organophosphate, carbamate, and organochlorine pesticides; petroleum hydrocarbons; biomarkers; and polynuclear aromatic hydrocarbons. The objectives were to determine the concentrations of these contaminants in water and suspended sedim
Authors
Joseph L. Domagalski, K.M. Kuivila
New reference materials for nitrogen-isotope-ratio measurements
Three new reference materials were manufactured for calibration of relative stable nitrogen‐isotope‐ratio measurements:USGS25 (ammonium sulfate) δ615″=−30 per milUSGS26 (ammonium sulfate) δ615″=+54 per milUSGS32 (potassium nitrate) δ615″=+180 per milwhere δN′, relative to atmospheric nitrogen, is an approximate value subject to change following interlaboratory comparisons. These materials are isot
Authors
John K. Böhlke, C. J. Gwinn, T. B. Coplen
Application of borehole geophysics in defining the wellhead protection area for a fractured crystalline bedrock aquifer
Wellbore geophysical techniques were used to characterize fractures and flow in a bedrock aquifer at a site near Blackwater Brook in Dover, New Hampshire. The primary focus ofthis study was the development of a model to assist in evaluating the area surrounding a planned water supply well where contaminants introduced at the land surface might be induced to flow towards a pumping well. Well logs a
Authors
J.H. Vernon, F.L. Paillet, W.H. Pedler, W.J. Griswold
An efficient numerical solution of the transient storage equations for solute transport in small streams
Several investigators have proposed solute transport models that incorporate the effects of transient storage. Transient storage occurs in small streams when portions of the transported solute become isolated in zones of water that are immobile relative to water in the main channel (e.g., pools, gravel beds). Transient storage is modeled by adding a storage term to the advection-dispersion equatio
Authors
Robert L. Runkel, Steven C. Chapra
The effect of streambed topography on surface-subsurface water exchange in mountain catchments
A numerical hydrological simulation suggested that water exchange between stream channels and adjacent aquifers is enhanced by convexities and concavities in streambed topography. At St. Kevin Gulch, an effluent stream in the Rocky Mountains of Colorado, subsurface hydraulic gradients and movement of ionic tracers indicated that stream water was locally recharged into well-defined flow paths throu
Authors
Judson W. Harvey, Kenneth E. Bencala
A perspective on stream-catchment connections
Ecological study of the hyporheic zone is leading to recognition of a need for additional hydrologic understanding. Some of this understanding can be obtained by viewing the hyporheic zone as a succession of isolated boxes adjacent to the stream. Further understanding, particularly relevant to catchment-scale ecology, may come from studies focussed on the fluid mechanics of the flow-path connectio
Authors
Kenneth E. Bencala
Monte Carlo simulations of multiphase flow incorporating spatial variability of hydraulic properties
To study the effect of spatial variability of sediment hydraulic properties on multiphase flow, oil infiltration into a hypothetical glacial outwash aquifer, followed by oil extraction, was simulated using a cross-sectional multiphase flow model. The analysis was simplified by neglecting capillary hysteresis. The first simulation used a uniform mean permeability and mean retention curve. This was
Authors
Hedeff I. Essaid, Kathryn M. Hess
Nonpoint source contamination of the Mississippi river and its tributaries by herbicides
A study of the Mississippi River and its tributaries during July-August 1991, October-November 1991, and April-May 1992 has indicated that the entire navigable reach of the river is contaminated with a complex mixture of agrochemicals and their transformation products derived from nonpoint sources. Twenty-three compounds were identified, including triazine, chloroacetanilide, thiocarbamate, phenyl
Authors
W. E. Pereira, F. D. Hostettler