Occurrence and turnover of nitric oxide in a nitrogen-impacted sand and gravel aquifer
R. L. Smith, T. Yoshinari
2008, Environmental Science & Technology (42) 8245-8251
Little is known about nitric oxide (NO) production or consumption in the subsurface, an environment which may be conducive to NO accumulation. A study conducted in a nitrogen-contaminated aquifer on Cape Cod, Massachusetts assessed the occurrence and turnover of NO within a contaminant plume in which nitrification...
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...
Wetlands as principal zones of methylmercury production in southern Louisiana and the Gulf of Mexico region
B.D. Hall, G. R. Aiken, D. P. Krabbenhoft, M. Marvin-DiPasquale, C.M. Swarzenski
2008, Environmental Pollution (154) 124-134
It is widely recognized that wetlands, especially those rich in organic matter and receiving appreciable atmospheric mercury (Hg) inputs, are important sites of methylmercury (MeHg) production. Extensive wetlands in the southeastern United States have many ecosystem attributes ideal for promoting high MeHg production rates; however, relatively few mercury cycling studies...
Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region
Michelle Ann Walvoord, Brian J. Andraski, D. P. Krabbenhoft, Robert G. Striegl
2008, Applied Geochemistry (23) 572-583
Mercury contained in buried landfill waste may be released via upward emission to the atmosphere or downward leaching to groundwater. Data from the US Geological Survey’s Amargosa Desert Research Site (ADRS) in arid southwestern Nevada reveal another potential pathway of Hg release: long-distance (102 m) lateral migration of elemental Hg (Hg0)...
Developing conceptual hydrogeological model for Potsdam sandstones in southwestern Quebec, Canada
Miroslav Nastev, R. Morin, Rejean Godin, Alain Rouleau
2008, Hydrogeology Journal (16) 373-388
A hydrogeological study was conducted in Potsdam sandstones on the international border between Canada (Quebec) and the USA (New York). Two sandstone formations, arkose and conglomerate (base) and well-cemented quartz arenite (upper), underlie the study area and form the major regional aquifer unit. Glacial till, littoral sand and gravel, and...
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...
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...
Changes in the character of DOC in streams during storms in two Midwestern watersheds with contrasting land uses
P. Vidon, L.E. Wagner, E. Soyeux
2008, Biogeochemistry (88) 257-270
Dissolved organic carbon (DOC) dynamics in streams is important, yet few studies focus on DOC dynamics in Midwestern streams during storms. In this study, stream DOC dynamics during storms in two Midwestern watersheds with contrasting land uses, the change in character of stream DOC during storms, and the usability of...
Nutrient dynamics as indicators of karst processes: Comparison of the Chalk aquifer (Normandy, France) and the Edwards aquifer (Texas, U.S.A.)
B.J. Mahler, D. Valdes, M. Musgrove, N. Massei
2008, Journal of Contaminant Hydrology (98) 36-49
Karst aquifers display a range of geologic and geomorphic characteristics in a wide range of climatic and land-use settings; identification of transport dynamics representative of karst aquifers in general could help advance our understanding of these complex systems. To this end, nutrient, turbidity, and major ion dynamics in response to...
Inverse modeling of surface-water discharge to achieve restoration salinity performance measures in Florida Bay, Florida
E.D. Swain, D.E. James
2008, Journal of Hydrology (351) 188-202
The use of numerical modeling to evaluate regional water-management practices involves the simulation of various alternative water-delivery scenarios, which typically are designed intuitively rather than analytically. These scenario simulations are used to analyze how specific water-management practices affect factors such as water levels, flows, and salinities. In lieu of testing...
Distinguishing black carbon from biogenic humic substances in soil clay fractions
D.A. Laird, M.A. Chappell, D.A. Martens, R.L. Wershaw, M. Thompson
2008, Geoderma (143) 115-122
Most models of soil humic substances include a substantial component of aromatic C either as the backbone of humic heteropolymers or as a significant component of supramolecular aggregates of degraded biopolymers. We physically separated coarse (0.2–2.0 μm e.s.d.), medium (0.02–0.2 μm e.s.d.), and fine (> 0.02 μm e.s.d.)...
Factors controlling nitrogen release from two forested catchments with contrasting hydrochemical responses
S.F. Christopher, M.J. Mitchell, Michael McHale, E.W. Boyer, Douglas A. Burns, C. Kendall
2008, Hydrological Processes (22) 46-62
Quantifying biogeochemical cycles of nitrogen (N) and the associated fluxes to surface waters remains challenging, given the need to deal with spatial and temporal variability and to characterize complex and heterogeneous landscapes. We focused our study on catchments S14 and S15 located in the Adirondack Mountains...
A comparative analysis of simulated and observed landslide locations triggered by Hurricane Camille in Nelson County, Virginia
M.M. Morrissey, G. F. Wieczorek, B. A. Morgan
2008, Hydrological Processes (22) 524-531
In 1969, Nelson County, Virginia received up to 71 cm of rain within 12 h starting at 7 p.m. on August 19. The total rainfall from the storm exceeded the 1000-year return period in the region. Several thousands of landslides were induced by rainfall associated with Hurricane Camille causing fatalities...
A biodynamic understanding of dietborne metal uptake by a freshwater invertebrate
M.-N. Croteau, S. N. Luoma
2008, Environmental Science & Technology (42) 1801-1806
Aquatic organisms accumulate metals from dissolved and particulate phases. Dietborne metal uptake likely prevails in nature, but the physiological processes governing metal bioaccumulation from diet are not fully understood. We characterize dietborne copper, cadmium, and nickel uptake by a freshwater gastropod (Lymnaea stagnalis) both in terms of biodynamics and membrane...
Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties
T.H. Boyer, P.C. Singer, G. R. Aiken
2008, Environmental Science & Technology (42) 7431-7437
Ten isolates of aquatic dissolved organic matter (DOM) were evaluated to determine the effect that chemical properties of the DOM, such as charge density, aromaticity, and molecular weight, have on DOM removal by anion exchange. The DOM isolates were characterized as terrestrial, microbial, or intermediate humic substances...
Tile drainage as karst: Conduit flow and diffuse flow in a tile-drained watershed
K. E. Schilling, M. Helmers
2008, Journal of Hydrology (349) 291-301
The similarity of tiled-drained watersheds to karst drainage basins can be used to improve understanding of watershed-scale nutrient losses from subsurface tile drainage networks. In this study, short-term variations in discharge and chemistry were examined from a tile outlet collecting subsurface tile flow from a 963 ha agricultural watershed. Study...
Electricity generation by anaerobic bacteria and anoxic sediments from hypersaline soda lakes
L.G. Miller, R.S. Oremland
2008, Extremophiles (12) 837-848
Anaerobic bacteria and anoxic sediments from soda lakes produced electricity in microbial fuel cells (MFCs). No electricity was generated in the absence of bacterial metabolism. Arsenate respiring bacteria isolated from moderately hypersaline Mono Lake (Bacillus selenitireducens), and salt-saturated Searles Lake, CA (strain SLAS-1) oxidized lactate using arsenate...
Potential for 4-n-nonylphenol biodegradation in stream sediments
P. M. Bradley, L. B. Barber, D.W. Kolpin, P.B. McMahon, F. H. Chapelle
2008, Environmental Toxicology and Chemistry (27) 260-265
The potential for in situ biodegradation of 4-nonylphenol (4-NP) was investigated in three hydrologically distinct streams impacted by wastewater treatment plants (WWTPs) in the United States. Microcosms were prepared with sediments from each site and amended with [U-ring-14C]4-n-nonylphenol (4-n-NP) as a model test substrate. Microcosms prepared with sediment collected upstream...
Isotopic variations of dissolved copper and zinc in stream waters affected by historical mining
David M. Borrok, David Nimick, Richard B. Wanty, William I. Ridley
2008, Geochimica et Cosmochimica Acta (72) 329-344
Zinc and Cu play important roles in the biogeochemistry of natural systems, and it is likely that these interactions result in mass-dependent fractionations of their stable isotopes. In this study, we examine the relative abundances of dissolved Zn and Cu isotopes in a variety of stream waters draining six historical...
Subsurface microbial diversity in deep-granitic-fracture water in Colorado
J.W. Sahl, R. Schmidt, E.D. Swanner, K.W. Mandernack, A.S. Templeton, Thomas L. Kieft, R. L. Smith, W. E. Sanford, R.L. Callaghan, J.B. Mitton, J.R. Spear
2008, Applied and Environmental Microbiology (74) 143-152
A microbial community analysis using 16S rRNA gene sequencing was performed on borehole water and a granite rock core from Henderson Mine, a >1,000-meter-deep molybdenum mine near Empire, CO. Chemical analysis of borehole water at two separate depths (1,044 m and 1,004 m below the mine...
Chromium, chromium isotopes and selected trace elements, western Mojave Desert, USA
J. A. Izbicki, J.W. Ball, T.D. Bullen, S. J. Sutley
2008, Applied Geochemistry (23) 1325-1352
Chromium(VI) concentrations in excess of the California Maximum Contaminant Level (MCL) of 50 μg/L occur naturally in alkaline, oxic ground-water in alluvial aquifers in the western Mojave Desert, southern California. The highest concentrations were measured in aquifers eroded from mafic rock, but Cr(VI)...
Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 2. Chemical retention from diffusion and slow advection
Allen M. Shapiro, Robert A. Renken, Ronald W. Harvey, Michael R. Zygnerski, David W. Metge
2008, Water Resources Research (44)
A tracer experiment, using a nonreactive tracer, was conducted as part of an investigation of the potential for chemical and pathogen migration to public supply wells that draw groundwater from the highly transmissive karst limestone of the Biscayne aquifer in southeastern Florida. The tracer was injected into the formation over...
