Sources, transformations, and hydrological processes that control stream nitrate and dissolved organic matter concentrations during snowmelt in an upland forest
Stephen D. Sebestyen, Elizabeth W. Boyer, James B. Shanley, Carol Kendall, Daniel H. Doctor, George R. Aiken, Nobuhito Ohte
2008, Water Resources Research (44)
We explored catchment processes that control stream nutrient concentrations at an upland forest in northeastern Vermont, USA, where inputs of nitrogen via atmospheric deposition are among the highest in the nation and affect ecosystem functioning. We traced sources of water, nitrate, and dissolved organic matter (DOM) using stream water samples...
New global hydrography derived from spaceborne elevation data
B. Lehner, K.L. Verdin, A. Jarvis
2008, Eos, Transactions, American Geophysical Union (89) 93-94
To study the Earth system and to better understand the implications of global environmental change, there is a growing need for large-scale hydrographic data sets that serve as prerequisites in a variety of analyses and applications, ranging from regional watershed and freshwater conservation planning to global hydrological, climate, biogeochemical, and...
Stream denitrification across biomes and its response to anthropogenic nitrate loading
P. J. Mulholland, A. M. Helton, G. C. Poole, R. O. Hall Jr., S. K. Hamilton, B. J. Peterson, J. L. Tank, L. R. Ashkenas, L. W. Cooper, Clifford N. Dahm, W. K. Dodds, S.E.G. Findlay, S.V. Gregory, N. B. Grimm, S. L. Johnson, W. H. McDowell, J.L. Meyer, H. M. Valett, J.R. Webster, C. P. Arango, J. J. Beaulieu, M. J. Bernot, A. J. Burgin, C. L. Crenshaw, L. T. Johnson, B.R. Niederlehner, J. M. O’Brien, J. D. Potter, R.W. Sheibley, D. J. Sobota, S. M. Thomas
2008, Nature (452) 202-205
Anthropogenic addition of bioavailable nitrogen to the biosphere is increasing and terrestrial ecosystems are becoming increasingly nitrogen-saturated, causing more bioavailable nitrogen to enter groundwater and surface waters. Large-scale nitrogen budgets show that an average of about 20-25 per cent of the nitrogen added to the biosphere is exported from rivers...
Monitoring urban impacts on suspended sediment, trace element, and nutrient fluxes within the City of Atlanta, Georgia, USA: Program design, methodological considerations, and initial results
A. J. Horowitz, K. A. Elrick, J.J. Smith
2008, Hydrological Processes (22) 1473-1496
Atlanta, Georgia (City of Atlanta, COA), is one of the most rapidly growing urban areas in the US. Beginning in 2003, the US Geological Survey established a long-term water-quantity/quality monitoring network for the COA. The results obtained during the first 2 years have provided insights into the requirements needed to...
National, holistic, watershed-scale approach to understand the sources, transport, and fate of agricultural chemicals
P. D. Capel, K. A. McCarthy, J.E. Barbash
2008, Journal of Environmental Quality (37) 983-993
This paper is an introduction to the following series of papers that report on in-depth investigations that have been conducted at five agricultural study areas across the United States in order to gain insights into how environmental processes and agricultural practices interact to determine the transport and fate of agricultural...
Using heat to characterize streambed water flux variability in four stream reaches
H.I. Essaid, C.M. Zamora, K. A. McCarthy, J. R. Vogel, J.T. Wilson
2008, Journal of Environmental Quality (37) 1010-1023
Estimates of streambed water flux are needed for the interpretation of streambed chemistry and reactions. Continuous temperature and head monitoring in stream reaches within four agricultural watersheds (Leary Weber Ditch, IN; Maple Creek, NE; DR2 Drain, WA; and Merced River, CA) allowed heat to be used as a tracer to...
Effect of hydrological conditions on nitrous oxide, methane, and carbon dioxide dynamics in a bottomland hardwood forest and its implication for soil carbon sequestration
K. Yu, S.P. Faulkner, M.J. Baldwin
2008, Global Change Biology (14) 798-812
This study was conducted at three locations in a bottomland hardwood forest with a distinct elevation and hydrological gradient: ridge (high, dry), transition, and swamp (low, wet). At each location, concentrations of soil greenhouse gases (N2O, CH4, and CO2), their fluxes to the atmosphere, and soil redox potential (Eh) were...
Nitrogen fluxes through unsaturated zones in five agricultural settings across the United States
C.T. Green, L.H. Fisher, B.A. Bekins
2008, Journal of Environmental Quality (37) 1073-1085
The main physical and chemical controls on nitrogen (N) fluxes between the root zone and the water table were determined for agricultural sites in California, Indiana, Maryland, Nebraska, and Washington from 2004 to 2005. Sites included irrigated and nonirrigated fields; soil textures ranging from clay to sand; crops including corn,...
Influence of natural dissolved organic carbon on the bioavailability of mercury to a freshwater alga
P.R. Gorski, D.E. Armstrong, J.P. Hurley, D. P. Krabbenhoft
2008, Environmental Pollution (154) 116-123
Bioavailability of mercury (Hg) to Selenastrum capricornutum was assessed in bioassays containing field-collected freshwater of varying dissolved organic carbon (DOC) concentrations. Bioconcentration factor (BCF) was measured using stable isotopes of methylmercury (MeHg) and inorganic Hg(II). BCFs for MeHg in low-DOC lake water were significantly larger than those in mixtures of...
Middle to late cenozoic geology, hydrography, and fish evolution in the American Southwest
J.E. Spencer, G.R. Smith, T.E. Dowling
2008, Conference Paper, Special Paper of the Geological Society of America
An evaluation of the poorly understood Cenozoic hydrologic history of the American Southwest using combined geological and biological data yields new insights with implications for tectonic evolution. The Mesozoic Cordilleran orogen next to the continental margin of southwestern North America probably formed the continental divide. Mountain building migrated eastward to...
Characterization and cycling of atmospheric mercury along the central US Gulf Coast
M.A. Engle, M.T. Tate, D. P. Krabbenhoft, A. Kolker, M.L. Olson, E.S. Edgerton, J.F. DeWild, A.K. McPherson
2008, Applied Geochemistry (23) 419-437
Concentrations of atmospheric Hg species, elemental Hg (Hg∘), reactive gaseous Hg (RGM), and fine particulate Hg (Hg-PM2.5) were measured at a coastal site near Weeks Bay, Alabama from April to August, 2005 and January to May, 2006. Mean concentrations of the species were...
Inverse geochemical modeling of groundwater evolution with emphasis on arsenic in the Mississippi River Valley alluvial aquifer, Arkansas (USA)
M.U. Sharif, R.K. Davis, K.F. Steele, B. Kim, T.M. Kresse, J.A. Fazio
2008, Journal of Hydrology (350) 41-55
Inverse geochemical modeling (PHREEQC) was used to identify the evolution of groundwater with emphasis on arsenic (As) release under reducing conditions in the shallow (25-30 m) Mississippi River Valley Alluvial aquifer, Arkansas, USA. The modeling was based on flow paths defined by high-precision (??2 cm) water level contour map; X-ray...
Mercury, trace elements and organic constituents in atmospheric fine particulate matter, Shenandoah National Park, Virginia, USA: A combined approach to sampling and analysis
A. Kolker, M.A. Engle, W. H. Orem, J.E. Bunnell, H.E. Lerch, D. P. Krabbenhoft, M.L. Olson, J.D. McCord
2008, Geostandards and Geoanalytical Research (32) 279-293
Compliance with U.S. air quality regulatory standards for atmospheric fine particulate matter (PM2.5) is based on meeting average 24 hour (35 μ m−3) and yearly (15 μg m−3) mass‐per‐unit‐volume limits, regardless of PM2.5 composition. Whereas this presents a workable regulatory framework, information on particle composition is needed...
Ground-based thermography of fluvial systems at low and high discharge reveals potential complex thermal heterogeneity driven by flow variation and bioroughness
M.B. Cardenas, J. W. Harvey, A.I. Packman, D.T. Scott
2008, Hydrological Processes (22) 980-986
Temperature is a primary physical and biogeochemical variable in aquatic systems. Field‐based measurement of temperature at discrete sampling points has revealed temperature variability in fluvial systems, but traditional techniques do not readily allow for synoptic sampling schemes that can address temperature‐related questions with broad, yet detailed,...
Evaluation of statistical treatments of left-censored environmental data using coincident uncensored data sets: I. Summary statistics
Ronald C. Antweiler, Howard E. Taylor
2008, Environmental Science & Technology (42) 3732-3738
The main classes of statistical treatment of below-detection limit (left-censored) environmental data for the determination of basic statistics that have been used in the literature are substitution methods, maximum likelihood, regression on order statistics (ROS), and nonparametric techniques. These treatments, along with using all instrument-generated data (even those below detection),...
Sensitivity of wetland saturated hydraulic heads and water budgets to evapotranspiration
W.B. Shoemaker, S. Huddleston, C.L. Boudreau, A. M. O’Reilly
2008, Wetlands (28) 1040-1047
The sensitivity of wetland saturated hydraulic heads and water budgets to evapotranspiration (ET) was examined using a simplified hydrologic model and eight representations of ET. Estimates of ET that created the most reliable wetland saturated hydraulic heads and water budgets employed vegetation coefficients to correct potential ET, calculated by the...
Anthropogenic influences on the input and biogeochemical cycling of nutrients and mercury in Great Salt Lake, Utah, USA
D. Naftz, C. Angeroth, T. Kenney, B. Waddell, N. Darnall, S. Silva, C. Perschon, J. Whitehead
2008, Applied Geochemistry (23) 1731-1744
Despite the ecological and economic importance of Great Salt Lake (GSL), little is known about the input and biogeochemical cycling of nutrients and trace elements in the lake. In response to increasing public concern regarding anthropogenic inputs to the GSL ecosystem, the US Geological Survey (USGS) and US Fish and...
Analysis of chlorothalonil and three degradates in sediment and soil
M.L. Hladik, K.M. Kuivila
2008, Journal of Agricultural and Food Chemistry (56) 2310-2314
A method has been developed for the simultaneous extraction of chlorothalonil and three of its degradates (4-hydroxy-2,5,6-trichloroisophthalonitrile, 1-carbamoyl-3-cyano-4-hydroxy-2,5,6-trichlorobenzene, and 1,3-dicarbamoyl-2,4,5,6-tetrachlorobenzene) from soils and sediments; the compounds were extracted using sonication with acetone and isolation of the parent compound and matrix interferences from the degradates by solid phase extraction (SPE)....
The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed
P.J. Hernes, R.G.M. Spencer, R.Y. Dyda, B.A. Pellerin, P.A.M. Bachand, B.A. Bergamaschi
2008, Geochimica et Cosmochimica Acta (72) 5266-5277
Willow Slough, a seasonally irrigated agricultural watershed in the Sacramento River valley, California, was sampled weekly in 2006 in order to investigate seasonal concentrations and compositions of dissolved organic carbon (DOC). Average DOC concentrations nearly doubled from winter baseflow (2.75 mg L-1) to summer irrigation (5.14 mg L-1), while a...
Probable flood predictions in ungauged coastal basins of El Salvador
M.J. Friedel, M.E. Smith, A.M.E. Chica, D. Litke
2008, Conference Paper, Journal of Hydrologic Engineering
A regionalization procedure is presented and used to predict probable flooding in four ungauged coastal river basins of El Salvador: Paz, Jiboa, Grande de San Miguel, and Goascoran. The flood-prediction problem is sequentially solved for two regions: upstream mountains and downstream alluvial plains. In the upstream mountains, a set of...
Opposing environmental gradients govern vegetation zonation in an intermountain playa
J.S. Sanderson, N.B. Kotliar, D.A. Steingraeber
2008, Wetlands (28) 1060-1070
Vegetation zonation was investigated at an intermountain playa wetland (Mishak Lakes) in the San Luis Valley (SLV) of southern Colorado. Plant composition and abiotic conditions were quantified in six vegetation zones. Reciprocal transplants were performed to test the importance of abiotic factors in governing zonation. Abiotic conditions differed among several...
Flood trends and river engineering on the Mississippi River system
N. Pinter, A.A. Jemberie, J.W.F. Remo, R.A. Heine, B.S. Ickes
2008, Geophysical Research Letters (35)
Along >4000 km of the Mississippi River system, we document that climate, land-use change, and river engineering have contributed to statistically significant increases in flooding over the past 100-150 years. Trends were tested using a database of >8 million hydrological measurements. A geospatial database of historical engineering construction was used...
The importance of hydrology in restoration of bottomland hardwood wetland functions
R.G. Hunter, S.P. Faulkner, K.A. Gibson
2008, Wetlands (28) 605-615
Bottomland hardwood (BLH) forests have important biogeochemical functions and it is well known that certain structural components, including pulsed hydrology, hydric soils, and hydrophytic vegetation, enhance these functions. It is unclear, however, how functions of restored BLH wetlands compare to mature, undisturbed wetlands. We measured a suite of structural and...
Coupled effect of chemotaxis and growth on microbial distributions in organic-amended aquifer sediments: Observations from laboratory and field studies
M. Wang, R.M. Ford, R.W. Harvey
2008, Environmental Science & Technology (42) 3556-3562
The inter-relationship of growth and chemotactic response exhibited by two common soil-inhabiting bacteria was investigated to determine its impact on bacterial migration. Filter-chambers were used to simulate aquifer sediments characterized by vertical gradients of organic contaminants in both artificial groundwater flow systems in the laboratory and within...
Assessment of crop growth and soil water modules in SWAT2000 using extensive field experiment data in an irrigation district of the Yellow River Basin
Y. Luo, C. He, M. Sophocleous, Z. Yin, R. Hongrui, Z. Ouyang
2008, Journal of Hydrology (352) 139-156
SWAT, a physically-based, hydrological model simulates crop growth, soil water and groundwater movement, and transport of sediment and nutrients at both the process and watershed scales. While the different versions of SWAT have been widely used throughout the world for agricultural and water resources applications, little has been done to...
