Publications

This article discusses preliminary results from analyses of USGS hydrodynamic data collected as part of the 1994 Interagency Ecological Program entrapment zone study. The USGS took part in three 30-hour cruises and deployed instruments for measuring currents and salinity from April to June. This article primarily focuses on the analysis of data from five Acoustic Doppler Current ProUers (ADCPs) de

The ability of resource agencies to manage fish, wildlife and freshwater supplies of San Francisco Bay estuary requires an integrated knowledge of the relations between the biota and their physical environment. A key factor in these relations is the role of salinity in determining both the physical and the biological character of the estuary. The saltiness of the water, and particularly its season

Estuaries are transitional ecosystems at the interface of the terrestrial and marine realms. Their unique physiographic position gives rise to large spatial variability, and to dynamic temporal variability resulting, in part, from a variety of forces and fluxes at the oceanic and terrestrial boundaries. River flow, in particular, is an important mechanism for delivering watershed-derived materials

A two-level model of the residual circulation and tidally-averaged salinity in San Francisco Bay has been developed in order to interpret long-term (days to decades) salinity variability in the Bay. Applications of the model to biogeochemical studies are also envisaged. The model has been used to simulate daily-averaged salinity in the upper and lower levels of a 51-segment discretization of the B

PHREEQC is a computer program written in the C programming language that is designed to perform a wide variety of aqueous geochemical calculations. PHREEQC is based on an ion-association aqueous model and has capabilities for (1) speciation and saturation-index calculations, (2) reaction-path and advective-transport calculations involving specified irreversible reactions, mixing of solutions, mine

In 1992, the U.S. Geological Survey (USGS) determined the distribution of pesticides in near-surface aquifers of the midwestern USA to be much more widespread than originally determined during a 1991 USGS study. The frequency of pesticide detection increased from 28.4% during the 1991 study to 59.0% during the 1992 study. This increase in pesticide detection was primarily the result of a more sens

Weekly precipitation (rain and snow) samples were collected from 81 National Atmospheric Deposition Program/National Trends Network sites in the Midwestern and Northeastern United States for the analysis of herbicides. In addition, five high- elevation background sites along the Rocky Mountains and in Alaska were sampled to provide data on herbicides in precipitation at sites far from the study ar

The problem of the origin of the continental crust can be resolved into two fundamental questions: (1) the location and mechanisms of initial mantle extraction of the primitive crust and (2) the processes by which this primitive crust is converted into the continental crust that presently exists. We know that Archean continental crust is compositionally distinct from younger continental crust. Arc

No abstract available.

Rainwater and surface water from four sites in Germany (Bavaria and Lower Saxony) were analyzed for atrazine by enzyme immunoassay from June 1990 until October 1992. The limit of quantification of the immunoassay was 0.02 μg/L with a middle of the test at 0.2 μg/L. About 60 % of the samples contained measurable amounts of atrazine. Seasonal trends were observed, with the highest concentration in t

Time histories of riverine water discharge, nitrate concentration, and nitrate, flux have been analyzed for the Mississippi and Atchafalaya rivers. Results indicate that water discharge variability is dominated by the annual cycle and shorter-time-scale episodic events presumably associated with snowmelt runoff and spring or summer rains. Interannual variability in water discharge is relatively sm

A study of U(VI) adsorption by ferrihydrite was conducted over a wide range of U(VI) concentrations, pH, and at two partial pressures of carbon dioxide. A two-site (strong- and weak-affinity sites, FesOH and FewOH, respectively) surface complexation model was able to describe the experimental data well over a wide range of conditions, with only one species formed with each site type: an inner-sphe