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An analysis of Cl- concentrations and fluxes at the Panola Mountain Research Watershed indicates that Cl- may be effectively used to differentiate "new" and "old" water flow through the hillslope and their respective contributions to streamwater. Rainfall and throughfall, the "new" water inputs, are marked by low Cl- concentrations (<15...

The potential threats to humans and to terrestrial and aquatic ecosystems from environmental contamination could depend on the sum of the concentrations of different chemicals. However, direct summation of environmental data is not generally feasible because it is common for some chemical concentrations to be recorded as being below the...

Paleoclimatic records from Mesoamerica document the interplay between Atlantic and Pacific sources of precipitation during the last glacial stage and Holocene. Today, and throughout much of the Holocene, the entire region receives its principal moisture in the summer from an interaction of easterly trade winds with the equatorial calms. Glacial...

Caddo Lake, situated on the border of northeast Texas and northwest Louisiana, USA is a medium-sized lake dominated by stands of baldcypress (Taxodiwn distichum). A study of tree growth was initiated at Caddo Lake to address concerns about the health of the baldcypress ecosystem. The lake has been subjected to...

The chemical relationships among particulate and colloidal organic material and dissolved fulvic acid were examined in an alpine and subalpine lake and two streams in Loch Vale Watershed, Rocky Mountain National Park. The alpine lake, Sky Pond, had the lowest dissolved organic carbon (DOC) (0.37 mgC/L), the highest particulate carbon...

I simulated the annual population cycles of Great Egrets (Ardea alba) at Lake Okeechobee, Florida, to provide a framework for evaluating the local population dynamics of nesting and foraging wading birds. The external forcing functions were solar energy, minimum air temperature, water depth, surface-water drying rate, and season. Solar input...

Rain and surface water samples from Southern Germany were investigated from 1991 to 1995 for terbuthylazine and one of its major metabolites, deethylterbuthylazine. The concentrations observed were compared to the concentrations found for atrazine and deethylatrazine in the same water samples. Concentrations ranged from < 0.02 μg/L to 0.7 μg/L...

Many wetlands undergo seasonal cycles in precipitation and water depth. This environmental seasonality is echoed in patterns of production of fish biomass, which, in turn, influence the phenology of other components of the food web, including wading birds. Human activities, such as drainage or other alterations of the hydrology, can...

In a column experiment, acidic groundwater from Pinal Creek Arizona, a Cu mining area, was eluted through a composited alluvial sample obtained from a core that had been removed from a well downgradient of the acidic groundwater. The minerals present in typical grains and flakes in the alluvium before and...

Controlled debris-flow initiation experiments focused on three hydrologic conditions that can trigger slope failure: localized ground-water inflow; prolonged moderate-intensity rainfall; and high-intensity rainfall. Detailed monitoring of slope hydrology and deformation provided exceptionally complete data on conditions preceding and accompanying slope failure and debris-flow mobilization. Ground-water inflow and high-intensity sprinkling led...

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 simultaneously with heterogeneity,...

No abstract available....

Variability and unpredictability are characteristics of the aquatic ecosystems, hydrological patterns and climate of the largely dryland region that encompasses the Basin and Range, American Southwest and western Mexico. Neither hydrological nor climatological models for the region are sufficiently developed to describe the magnitude...

The effect of tributary inflows on metal concentrations in <63-μm sediments and benthic insects was examined on two scales (380 km and <2 km) in a river impacted by mining. A dilution−mixing model effectively described large-scale dispersion of Cd, Cu, and Pb in the sediments of the...

The Great Plains landscape is less topographically complex than most other regions within North America, but diverse aquatic ecosystems, such as playas, pothole lakes, ox-bow lakes, springs, groundwater aquifers, intermittent and ephemeral streams, as well as large rivers and wetlands, are highly dynamic and responsive to extreme climatic fluctuations. We...

Natural surficial accumulations of nitrate-rich salts in the Atacama Desert, northern Chile, and in the Death Valley region of the Mojave Desert, southern California, are well known, but despite many geologic and geochemical studies, the origins of the nitrates have remained controversial. N...

Eukaryotic microorganisms (protists) are a very important component of microbial communities inhabiting groundwater aquifers This is not unexpected when one considers that many protists feed heterotrophically, by means of either phagotrophy (bacterivory) or osmotrophy. Protistan numbers are usually low (<102 per g dw of aquifer material) in pristine, uncontaminated aquifers...

The oxidation of methyl bromide (MeBr) in the water column of Mono Lake, CA, was studied by measuring the formation of H14CO3 from [14C]MeBr. Potential oxidation was detected throughout the water column, with highest rates occurring in the epilimnion (5-12 m depth). The oxidation of MeBr was eliminated by filter-sterilization,...

To test the effects of sewage-derived organic matter on virus attachment, 32P-labeled bacteriophage PRD1, linear alkylbenzene sulfonates (LAS), and tracers were injected into sewage-contaminated (suboxic, elevated organic matter) and uncontaminated (oxic, low organic matter) zones of an iron oxide-coated quartz sand and gravel aquifer on Cape Cod, MA. In the...

The clustering of orientations of hydraulically conductive fractures in bedrock at the Mirror Lake, New Hampshire fractured rock study site was investigated by comparing the orientations of fracture populations in two subvertical borehole arrays with those mapped on four adjacent subvertical roadcuts. In the boreholes and the roadcuts, the orientation...

Six geologic units are recognized in the Cretaceous and the Paleocene sediments of eastern Burke and Screven Counties in Georgia on the basis of lithologic, geophysical, and paleontologic data collected from three continuously cored testholes in Georgia and one testhole in South Carolina. The six geologic units are separated by...

The detection of the sulfonic acid metabolites of the chloroacetanilide herbicides acetochlor, alachlor, butachlor, propachlor, and, more recently, metolachlor in surface and ground water suggests that a common mechanism for dechlorination exists via the glutathione conjugation pathway. The identification of these herbicides and their metabolites is important due to growing...

The Mammoth Corridor in and adjacent to Yellowstone National Park encompasses a N-S alignment of geothermal features that extends from the Norris Geyser Basin adjacent to the Yellowstone caldera through Mammoth Hot Springs to the Corwin Springs Known Geothermal Resources Area (KGRA). Thermal springs in this region discharge water that...

Groundwater brine seepage into the Dolores River in Paradox Valley, Colorado, increases the dissolved solids load of the Colorado River annually by ∼2.0 × 108 kg. To abate this natural contamination, the Bureau of Reclamation plans to pump ∼3540 m3/d of brine from 12 shallow wells located along the Dolores River....

Two sets of hydrologic indices were developed to characterize the water-budget components of nontidal wetlands. The first set consisted of six water-budget indices for input and output variables, and the second set consisted of two hydrologic interaction indices derived from the water-budget indices. The indices then were applied to 19...