Publications

Suspended material samples were collected at 16 sites along the Mississippi River and some of its tributaries during July-August 1991, October-November 1991, and April-May 1992, and separated into colloid and particulate fractions to determine the organic carbon content of these two fractions of suspended material. Sample collection involved centrifugation to isolate the suspended...

Single-well injection/recovery tracer tests are considered for use in characterizing and quantifying matrix diffusion in dual-porosity aquifers. Numerical modeling indicates that neither regional drift in homogeneous aquifers, nor heterogeneity in aquifers having no regional drift, nor hydrodynamic dispersion significantly affects these tests. However, when drift is coupled...

The aquifer of western Cape Cod consists of several hydrogeologic units composed of sand, gravel, silt, and clay (fig. 1) that were deposited during the late Wisconsinan glaciation of New England. The aquifer is a shallow, unconfined hydrologic system in which ground-water flows radially outward from the apex of the ground-water mound near the center of the peninsula toward the coast...

The U.S. Geological Survey conducted hydrologic investigations in San Francisco Bay between January and November of 1995. Dissolved inorganic plant nutrients, nitrate, nitrite, ammonium, silica, and reactive phosphorus were measured in surface and in near-bottom waters at previously established locations in the channel portions of both northern and southern reaches of the bay, and at...

Nitrate in surface water can have adverse effects on aquatic life and, in drinking-water supplies, can be a risk to human health. As part of a regional study, nitrates as N (NO3-N) was analyzed in water samples collected from streams throughout 10 Midwestern states during synoptic surveys in 1989, 1990, and 1994. Data from the period immediately following crop planting at 124 sites were...

To find out, scientists from the U. S. Geological Survey (USGS) tested walleye and other sport fish from the upper Columbia River and Franklin D. Roosevelt Lake (Lake Roosevelt), the largest reservoir in Washington and a popular fishing spot. Findings: Walleye had higher concentrations of mercury than other sport fish. Larger walleye had higher mercury concentrations than smaller walleye...

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...

The research site at Otis Air Base, Cape Cod, Massachusetts, has been developed for hydrogeological and geochemical studies of sewage-effluent contaminated groundwater since 1982. Research of hydrologic properties, transport, and chemical and biological processes is ongoing, but the origin of background water chemistry has not been determined. The principal geochemical process giving...

Determination of fetch requirements for accurate Bowen-ratio measurements of latent- and sensible-heat fluxes is more involved than for eddy-correlation measurements because Bowen-ratio sensors are located at two heights, rather than just one. A simple solution to the diffusion equation is used to derive an expression for Bowen-ratio fetch requirements, downwind of a step change in...

While 'water quality function' is cited as an important wetland function to design for and preserve, we demonstrate that the scale at which hydrochemical samples are collected can significantly influence interpretations of biogeochemical processes in wetlands. Subsurface, chemical profiles for both nutrients and major ions were determined at a site in southwestern Wisconsin that...

Infiltration and dispersion (including molecular diffusion) can transport volatile organic compounds (VOCs) from urban air into shallow groundwater. The gasoline additive methyl-tert-butyl ether (MTBE) is of special interest because of its (1) current levels in some urban air, (2) strong partitioning from air into water, (3) resistance to degradation, (4) use as an octane-booster since...

Assimilation efficiencies (AEs) and physiological turnover-rate constants (k) of six trace elements (Ag, Am, Cd, Co, Se, Zn) in four marine bivalves (Crassostrea virginica Gmelin,Macoma balthica Linnaeus, Mercenaria mercenaria Linnaeus, and Mytilus edulis Linnaeus) were measured in radiotracer-depuration experiments. Egestion rates of unassimilated elements were highest during the first...