Potential for nonenzymatic reduction of Fe(III) via electron shuttling in subsurface sediments
Kelly P. Nevin, Derek R. Lovely
2000, Environmental Science & Technology (34) 2472-2478
The potential for various substances to serve as electron shuttles between Fe(III)-reducing microorganisms and insoluble Fe(III) oxides in aquifer sediments was evaluated in order to determine whether abiological mechanisms might play a role in the apparent microbial reduction of Fe(III) in subsurface sediments. Humic substances (humics) and the humics analogue,...
Groundwater “fast paths” in the Snake River Plain aquifer: Radiogenic isotope ratios as natural groundwater tracers
Thomas M. Johnson, Robert C. Roback, Travis L. McLing, Thomas D. Bullen, Donald J. DePaolo, Christine Doughty, Randall J. Hunt, Robert W. Smith, L. DeWayne Cecil, Michael T. Murrell
2000, Geology (28) 871-874
Preferential flow paths are expected in many groundwater systems and must be located because they can greatly affect contaminant transport. The fundamental characteristics of radiogenic isotope ratios in chemically evolving waters make them highly effective as preferential flow path indicators. These ratios tend to be more easily interpreted than solute-concentration...
Characteristic length scale of input data in distributed models: implications for modeling grain size
Guleid A. Artan, C. M. U. Neale, D. G. Tarboton
2000, Journal of Hydrology (227) 128-139
The appropriate spatial scale for a distributed energy balance model was investigated by: (a) determining the scale of variability associated with the remotely sensed and GIS-generated model input data; and (b) examining the effects of input data spatial aggregation on model response. The semi-variogram and the characteristic length calculated from...
Treatment of internal sources in the finite-volume ELLAM
R. W. Healy
Bentley L.R., Sykes J.F., Brebbia C.A., Gray W.G., Pinder G.F., editor(s)
2000, Conference Paper, Computational methods in water resources - Volume 2 - Computational methods,surface water systems and hydrology
The finite-volume Eulerian-Lagrangian localized adjoint method (FVELLAM) is a mass-conservative approach for solving the advection-dispersion equation. The method has been shown to be accurate and efficient for solving advection-dominated problems of solute transport in ground water in 1, 2, and 3 dimensions. Previous implementations of FVELLAM have had difficulty in...
Classification of river regimes: A context for hydroecology
W. R. Osterkamp, Jonathan M. Friedman
2000, Hydrological Processes (14) 2831-2848
Over the past 30 years, ecologists have demostrated the importance of flow and temperature as primary variables in driving running water, riparian and floodplain ecosystems. As it is important to assess the size and timing of discharge variations in relation to those in temperature, a method is proposed that uses...
The disparity between extreme rainfall events and rare floods - with emphasis on the semi-arid American West
W. R. Osterkamp, Jonathan M. Friedman
2000, Hydrological Processes (14) 2817-2829
Research beginning 40 years ago suggested that semi-arid lands of the USA have higher unit discharges for a given recurrence interval than occur in other areas. Convincing documentation and arguments for this suspicion, however, were not presented. Thus, records of measured rainfall intensities for specified durations and recurrence intervals, and...
Test functions for three-dimensional control-volume mixed finite-element methods on irregular grids
R.L. Naff, T.F. Russell, J. D. Wilson
Bentley L.R., Sykes J.F., Brebbia C.A., Gray W.G., Pinder G.F., editor(s)
2000, Conference Paper, Computational methods in water resources - Volume 2 - Computational methods,surface water systems and hydrology
Numerical methods based on unstructured grids, with irregular cells, usually require discrete shape functions to approximate the distribution of quantities across cells. For control-volume mixed finite-element methods, vector shape functions are used to approximate the distribution of velocities across cells and vector test functions are used to minimize the error...
An organized signal in snowmelt runoff over the western United States
D. H. Peterson, R. E. Smith, M. D. Dettinger, D.R. Cayan, L. Riddle
2000, Journal of the American Water Resources Association (36) 421-432
Daily-to-weekly discharge during the snowmelt season is highly correlated among river basins in the upper elevations of the central and southern Sierra Nevada (Carson, Walker, Tuolumne, Merced, San Joaquin, Kings, and Kern Rivers). In many cases, the upper Sierra Nevada watershed operates in a single mode (with varying catchment amplitudes)....
Determining timescales for groundwater flow and solute transport
Peter G. Cook, J.K. Bohlke
Peter G. Cook, Andrew L. Herczeg, editor(s)
2000, Book chapter, Environmental tracers in subsurface hydrology
One of the principal uses of environmental tracers is for determining the ages of soil waters and groundwaters. (We may refer to this as ‘hydrochronology’by analogy with the dating of solid materials known as geochronology.) Information on soil water and groundwater age enables timescales for a range of subsurface processes...
Contaminant sorption by soil and bed sediment: Is there a difference?
C. T. Chiou, D. E. Kile
2000, Fact Sheet 087-00
No abstract available. ...
Organic matter sources and rehabilitation of the Sacramento-San Joaquin Delta (California, USA)
A.D. Jassby, James E. Cloern
2000, Aquatic Conservation: Marine and Freshwater Ecosystems (10) 323-352
1. The Sacramento San Joaquin River Delta, a complex mosaic of tidal freshwater habitats in California, is the focus of a major ecosystem rehabilitation effort because of significant long-term changes in critical ecosystem functions. One of these functions is the production, transport and transformation of organic matter that constitutes the...
Annual bed-elevation regime in the alluvial channel of Squamish River, southwestern British Columbia Canada
S.D. Stanford, M.A. Seidl, G.M. Ashley
2000, Earth Surface Processes and Landforms (25) 991-1009
The aim of this study is to examine the annual regime of channel scour and fill by monitoring bed-elevation changes in a reach of Squamish River in southwestern British Columbia, Canada. Sonar surveys of 13 river cross-sections in a sandy gravel-bed single-channel study reach were repeated biweekly over a full...
Characterization of U(VI)-carbonato ternary complexes on hematite: EXAFS and electrophoretic mobility measurements
John R. Bargar, Rebecca Reitmeyer, John J. Lenhart, James A. Davis
2000, Geochimica et Cosmochimica Acta (64) 2737-2749
We have measured U(VI) adsorption on hematite using EXAFS spectroscopy and electrophoresis under conditions relevant to surface waters and aquifers (0.01 to 10 μM dissolved uranium concentrations, in equilibrium with air, pH 4.5 to 8.5). Both techniques suggest the existence of anionic U(VI)-carbonato ternary complexes. Fits to EXAFS spectra indicate...
Influence of acid volatile sulfide and metal concentrations on metal bioavailability to marine invertebrates in contaminated sediments
B.-G. Lee, J.-S. Lee, S. N. Luoma, H.J. Choi, C.-H. Koh
2000, Environmental Science & Technology (34) 4517-4523
An 18-day microcosm study was conducted to evaluate the influence of acid volatile sulfides (AVS) and metal additions on bioaccumulation from sediments of Cd, Ni, and Zn in two clams (Macoma balthica and Potamocorbula amurensis) and three marine polychaetes (Neanthes arenaceodentata, Heteromastus filiformis, and Spiophanes missionensis). Manipulation of AVS by oxidation...
Influence of a nonionic surfactant (Triton X-100) on contaminant distribution between water and several soil solids
J.-F. Lee, P.-M. Liao, C.-C. Kuo, H.-T. Yang, C. T. Chiou
2000, Journal of Colloid and Interface Science (229) 445-452
The influence of a nonionic surfactant (Triton X-100) on the contaminant distribution coefficients in solid–water mixtures was determined for a number of relatively nonpolar compounds (contaminants) on several natural solids. The studied compounds consisted of BTEX (benzene, toluene, ethylbenzene, and p-xylene) and chlorinated pesticides...
Strontium isotope geochemistry of groundwaters and streams affected by agriculture, Locust Grove, MD
J.K. Böhlke, M. Horan
2000, Applied Geochemistry (15) 599-609
The effects of agriculture on the isotope geochemistry of Sr were investigated in two small watersheds in the Atlantic coastal plain of Maryland. Stratified shallow oxic groundwaters in both watersheds contained a retrievable record of increasing recharge rates of chemicals including NO3−, Cl, Mg, Ca and Sr that were correlated...
Restoration of biogeochemical function in mangrove forests
K.L. McKee, P.L. Faulkner
2000, Restoration Ecology (8) 247-259
Forest structure of mangrove restoration sites (6 and 14 years old) at two locations (Henderson Creek [HC] and Windstar [WS]) in southwest Florida differed from that of mixed-basin forests (>50 years old) with which they were once contiguous. However, the younger site (HC) was typical of natural, developing forests, whereas...
Bacterial dissimilatory reduction of arsenate and sulfate in meromictic Mono Lake, California
R.S. Oremland, P.R. Dowdle, S. Hoeft, J.O. Sharp, J.K. Schaefer, L.G. Miller, Blum J. Switzer, R. L. Smith, N.S. Bloom, D. Wallschlaeger
2000, Geochimica et Cosmochimica Acta (64) 3073-3084
The stratified (meromictic) water column of alkaline and hypersaline Mono Lake, California, contains high concentrations of dissolved inorganic arsenic (~200 ??mol/L). Arsenic speciation changes from arsenate [As (V)] to arsenite [As (III)] with the transition from oxic surface waters (misolimnion) to anoxic bottom waters (monimolimnion). A radioassay was devised to...
Estimating formation properties from early-time oscillatory water levels in a pumped well
A.M. Shapiro, D.S. Oki
2000, Journal of Hydrology (236) 91-108
Hydrologists often attempt to estimate formation properties from aquifer tests for which only the hydraulic responses in a pumped well are available. Borehole storage, turbulent head losses, and borehole skin, however, can mask the hydraulic behavior of the formation inferred from the water level in the pumped well. Also, in...
Concentrations and characteristics of organic carbon in surface water in Arizona: Influence of urbanization
P. Westerhoff, D. Anning
2000, Journal of Hydrology (236) 202-222
Dissolved (DOC) and total (TOC) organic carbon concentrations and compositions were studied for several river systems in Arizona, USA. DOC composition was characterized by ultraviolet and visible absorption and fluorescence emission (excitation wavelength of 370 nm) spectra characteristics. Ephemeral sites had the highest DOC concentrations, and unregulated perennial sites had...
Methodology and application of combined watershed and ground-water models in Kansas
M. Sophocleous, S.P. Perkins
2000, Journal of Hydrology (236) 185-201
Increased irrigation in Kansas and other regions during the last several decades has caused serious water depletion, making the development of comprehensive strategies and tools to resolve such problems increasingly important. This paper makes the case for an intermediate complexity, quasi-distributed, comprehensive, large-watershed model, which falls between the fully distributed,...
Occurrence of sulfonylurea, sulfonamide, imidazolinone, and other herbicides in rivers, reservoirs and ground water in the Midwestern United States, 1998
W.A. Battaglin, E. T. Furlong, M.R. Burkhardt, C.J. Peter
2000, Science of Total Environment (248) 123-133
Sulfonylurea (SU), sulfonamide (SA), and imidazolinone (IMI) herbicides are relatively new classes of chemical compounds that function by inhibiting the action of a plant enzyme, stopping plant growth, and eventually killing the plant. These compounds generally have low mammalian toxicity, but plants demonstrate a...
Attenuation-difference radar tomography: Results of a multiple-plane experiment at the U.S. Geological Survey Fractured-Rock Research Site, Mirror Lake, New Hampshire
J.W. Lane Jr., F. D. Day-Lewis, J.M. Harris, F.P. Haeni, S.M. Gorelick
2000, Conference Paper, Proceedings of SPIE - The International Society for Optical Engineering
Attenuation-difference, borehole-radar tomography was used to monitor a series of sodium chloride tracer injection tests conducted within the FSE, wellfield at the U.S. Geological Survey Fractured-Rock Hydrology Research Site in Grafton County, New Hampshire, USA. Borehole-radar tomography surveys were conducted using the sequential-scanning and injection method in three boreholes that...
Characterizing multiple timescales of stream and storage zone interaction that affect solute fate and transport in streams
Jungyill Choi, Judson W. Harvey, Martha H. Conklin
2000, Water Resources Research (36) 1511-1518
The fate of contaminants in streams and rivers is affected by exchange and biogeochemical transformation in slowly moving or stagnant flow zones that interact with rapid flow in the main channel. In a typical stream, there are multiple types of slowly moving flow zones in which exchange and transformation occur,...
Shallow subsurface storm flow in a forested headwater catchment: Observations and modeling using a modified TOPMODEL
Todd M. Scanlon, Jeff P. Raffensperger, George M. Hornberger, Roger B. Clapp
2000, Water Resources Research (36) 2575-2586
Transient, perched water tables in the shallow subsurface are observed at the South Fork Brokenback Run catchment in Shenandoah National Park, Virginia. Crest piezometers installed along a hillslope transect show that the development of saturated conditions in the upper 1.5 m of the subsurface is controlled by total precipitation and...
