Widespread natural perchlorate in unsaturated zones of the southwest United States
Balaji Rao, Todd A. Anderson, Greta J. Orris, Ken A. Rainwater, Srinath Rajagopalan, Renee M. Sandvig, Bridget R. Scanlon, David A. Stonestrom, Michelle Ann Walvoord, W Andrew Jackson
2007, Environmental Science & Technology (41) 4522-4528
A substantial reservoir (up to 1 kg ha-1) of natural perchlorate is present in diverse unsaturated zones of the arid and semi-arid southwestern United States. The perchlorate co-occurs with meteoric chloride that has accumulated in these soils throughout the Holocene [0...
Anthropogenic contaminants as tracers in an urbanizing karst aquifer
B. Mahler, N. Massei
2007, Journal of Contaminant Hydrology (91) 81-106
Karst aquifers are uniquely vulnerable to contamination. In the Barton Springs segment of the karstic Edwards aquifer (Texas, U.S.A.), urban contaminants such as pesticides and volatile organic compounds frequently are detected in spring base flow. To determine whether contaminant concentrations change in response to storms, and if they therefore might...
Effects of intraborehole flow on groundwater age distribution
B.A. Zinn, Leonard F. Konikow
2007, Hydrogeology Journal (15) 633-643
Environmental tracers are used to estimate groundwater ages and travel times, but the strongly heterogeneous nature of many subsurface environments can cause mixing between waters of highly disparate ages, adding additional complexity to the age-estimation process. Mixing may be exacerbated by the presence of wells because long open intervals or...
Field-derived relationships for flow velocity and resistance in high-gradient streams
F. Comiti, L. Mao, A. Wilcox, E.E. Wohl, M.A. Lenzi
2007, Journal of Hydrology (340) 48-62
We measured velocity and channel geometry in 10 reaches (bed gradient = 0.08-0.21) of a predominantly step-pool channel, the Rio Cordon, Italy, over a range of discharges (3-80% of the bankfull discharge). The resulting data were used to compute flow resistance. At-a-station hydraulic geometry relations indicate that in most reaches,...
Determining metal assimilation efficiency in aquatic invertebrates using enriched stable metal isotope tracers
Marie Noele Croteau, Samuel N. Luoma, B. Pellet
2007, Aquatic Toxicology (83) 116-125
We employ a novel approach that combines pulse-chase feeding and multi-labelled stable isotopes to determine gut passage time (GPT), gut retention time (GRT), food ingestion rate (IR) and assimilation efficiency (AE) of three trace elements for a freshwater gastropod. Lettuce isotopically enriched in 53Cr, 65Cu and 106Cd was fed for 2 h to Lymnaea stagnalis....
Geoelectrical evidence of bicontinuum transport in groundwater
K. Singha, Frederick D. Day-Lewis, John W. Lane Jr.
2007, Geophysical Research Letters (34)
Bicontinuum models and rate-limited mass transfer (RLMT) explain complex transport behavior (e.g., long tailing and rebound) in heterogeneous geologic media, but experimental verification is problematic because geochemical samples represent the mobile component of the pore space. Here, we present geophysical evidence of RLMT at the field scale during an aquifer-storage...
Increased groundwater to stream discharge from permafrost thawing in the Yukon River basin: Potential impacts on lateral export of carbon and nitrogen
Michelle Ann Walvoord, Robert G. Striegl
2007, Geophysical Research Letters (34)
Arctic and subarctic watersheds are undergoing climate warming, permafrost thawing, and thermokarst formation resulting in quantitative shifts in surface water - groundwater interaction at the basin scale. Groundwater currently comprises almost one fourth of Yukon River water discharged to the Bering Sea and contributes 5-10% of the dissolved organic carbon...
Altered stream-flow regimes and invasive plant species: The Tamarix case
J.C. Stromberg, S.J. Lite, R. Marler, C. Paradzick, P.B. Shafroth, D. Shorrock, J. M. White, M.S. White
2007, Global Ecology and Biogeography (16) 381-393
Aim: To test the hypothesis that anthropogenic alteration of stream-flow regimes is a key driver of compositional shifts from native to introduced riparian plant species. Location: The arid south-western United States; 24 river reaches in the Gila and Lower Colorado drainage basins of Arizona. Methods: We compared the abundance of...
Origin of halite brine in the Onondaga Trough near Syracuse, New York State, USA: Modeling geochemistry and variable-density flow
Richard M. Yager, William M. Kappel, Niel Plummer
2007, Hydrogeology Journal (15) 1321-1339
Halite brine (saturation ranging from 45 to 80%) lies within glacial sediments that fill the Onondaga Trough, a bedrock valley deepened by Pleistocene glaciation near Syracuse, New York State, USA. The most concentrated brine occupies the northern end of the trough, about 10 km downgradient of the northern limit of...
Bedrock aquifers and population growth in the Denver Basin, Colorado, USA
J.E. Moore, R.G. Raynolds, M. Dechesne
2007, Episodes (30) 115-118
The Denver Basin bedrock aquifer system consists of Tertiary and Cretaceous age sedimentary rocks known as the Dawson, Denver, Arapahoe and Laramie-Fox Hills aquifers. The number of bedrock wells has increased from 12,000 in 1985 to over 33,700 in 2001 and the withdrawal of groundwater has caused water level declines...
Phosphorus budgets in Everglades wetland ecosystems: The effects of hydrology and nutrient enrichment
G.B. Noe, D.L. Childers
2007, Wetlands Ecology and Management (15) 189-205
The Florida Everglades is a naturally oligotrophic hydroscape that has experienced large changes in ecosystem structure and function as the result of increased anthropogenic phosphorus (P) loading and hydrologic changes. We present whole-ecosystem models of P cycling for Everglades wetlands with differing hydrology and P enrichment with the goal of...
Isotopic characterization of three groundwater recharge sources and inferences for selected aquifers in the upper Klamath Basin of Oregon and California, USA
P.C. Palmer, M. W. Gannett, S.R. Hinkle
2007, Journal of Hydrology (336) 17-29
Stable isotope (??D and ??18O) signatures of three principal groundwater recharge areas in the 21,000-km2 upper Klamath Basin are used to infer recharge sources for aquifers in the interior parts of the basin. Two of the principal recharge areas, the Cascade Range on the western and southern margin of the...
Recent climate trends and implications for water resources in the Catskill Mountain region, New York, USA
Douglas A. Burns, Julian Klaus, Michael R. McHale
2007, Journal of Hydrology (336) 155-170
Climate scientists have concluded that the earth’s surface air temperature warmed by 0.6 °C during the 20th century, and that warming induced by increasing concentrations of greenhouse gases is likely to continue in the 21st century, accompanied by changes in the hydrologic cycle. Climate change has important implications in the Catskill...
Nitrification in the euphotic zone as evidenced by nitrate dual isotopic composition: Observations from Monterey Bay, California
Scott D. Wankel, Carol Kendall, J.T. Pennington, Francisco P. Chavez, Adina Paytan
2007, Global Biogeochemical Cycles (21)
Coupled measurements of nitrate (NO3−), nitrogen (N), and oxygen (O) isotopic composition (δ15NNO3 and δ18ONO3) were made in surface waters of Monterey Bay to investigate multiple N cycling processes occurring within surface waters. Profiles collected throughout the year at three sites exhibit a wide range of values, suggesting simultaneous...
Nutrient vectors and riparian processing: A review with special reference to African semiarid savanna ecosystems
Shayne M. Jacobs, J.S. Bechtold, Harry C. Biggs, N. B. Grimm, S. Lorentz, M.E. McClain, R.J. Naiman, Steven S. Perakis, G. Pinay, M.C. Scholes
2007, Ecosystems (10) 1231-1249
This review article describes vectors for nitrogen and phosphorus delivery to riparian zones in semiarid African savannas, the processing of nutrients in the riparian zone and the effect of disturbance on these processes. Semiarid savannas exhibit sharp seasonality, complex hillslope hydrology and high spatial heterogeneity, all of which ultimately impact...
Water table fluctuations under three riparian land covers, Iowa (USA)
K. E. Schilling
2007, Hydrological Processes (21) 2415-2424
Water table depth is known to play an important role in nitrogen cycling in riparian zones, but little detailed monitoring of water table fluctuations has been reported. In this study, results of high-resolution water table monitoring under three common riparian land covers (forest, cool season grass, corn) were analysed to...
Holocene sea level and climate change in the Black Sea: Multiple marine incursions related to freshwater discharge events
R.E. Martin, E. Leorri, P.P. McLaughlin
2007, Quaternary International (167-168) 61-72
Repeated marine invasions of the Black Sea during the Holocene have been inferred by many eastern scientists as resulting from episodes of marine inflow from the Mediterranean beneath a brackish outflow from the Black Sea. We support this scenario but a fundamental question remains: What caused the repeated marine invasions?...
Simulation of flow and habitat conditions under ice, Cache la Poudre River - January 2006
Terry Waddle
2007, Open-File Report 2007-1282
The U.S. Forest Service authorizes the occupancy and use of Forest Service lands by various projects, including water storage facilities, under the Federal Land Policy and Management Act. Federal Land Policy and Management Act permits can be renewed at the end of their term. The U.S. Forest Service analyzes the...
Diel cycling of zinc in a stream impacted by acid rock drainage: Initial results from a new in situ Zn analyzer
Thomas P. Chapin, David A. Nimick, Chris Gammons, Richard B. Wanty
2007, Environmental Monitoring and Assessment (133) 161-167
Recent work has demonstrated that many trace metals undergo dramatic diel (24-h) cycles in near neutral pH streams with metal concentrations reproducibly changing up to 500% during the diel period (Nimick et al., 2003). To examine diel zinc cycles in streams affected by acid rock drainage, we have developed a...
Monitoring engineered remediation with borehole radar
John W. Lane Jr., Frederick D. Day-Lewis, Peter K. Joesten
2007, The Leading Edge (26) 1032-1035
The success of engineered remediation is predicated on correct emplacement of either amendments (e.g., vegetable-oil emulsion, lactate, molasses, etc.) or permeable reactive barriers (e.g., vegetable oil, zero-valent iron, etc.) to enhance microbial or geochemical breakdown of contaminants and treat contaminants. Currently, site managers have limited tools to provide information about...
Thioarsenates in geothermal waters of Yellowstone National Park: Determination, preservation, and geochemical importance
B. Planer-Friedrich, J. London, R. Blaine McCleskey, D. Kirk Nordstrom, D. Wallschlager
2007, Environmental Science & Technology (41) 5245-5251
Mono-, di-, tri-, and tetrathioarsenate, as well as methylated arsenic oxy- and thioanions, were determined besides arsenite and arsenate in geothermal waters of Yellowstone National Park using anion-exchange chromatography inductively coupled plasma mass spectrometry. Retention time match with synthetic standards, measured S:As ratios, and molecular electrospray mass spectra support the...
Spatial and temporal variations in silver contamination and toxicity in San Francisco Bay
A.R. Flegal, Cynthia L. Brown, S. Squire, J.R.M. Ross, G.M. Scelfo, S. Hibdon
2007, Environmental Research (105) 34-52
Although San Francisco Bay has a "Golden Gate", it may be argued that it is the "Silver Estuary". For at one time the Bay was reported to have the highest levels of silver in its sediments and biota, along with the only accurately measured values of silver in solution, of...
Investigation of reductive dechlorination supported by natural organic carbon
Heather V. Rectanus, Mark A. Widdowson, Francis H. Chapelle, C.A. Kelly, John T. Novak
2007, Ground Water Monitoring and Remediation (27) 53-62
Because remediation timeframes using monitored natural attenuation may span decades or even centuries at chlorinated solvent sites, new approaches are needed to assess the long-term sustainability of reductive dechlorination in ground water systems. In this study, extraction procedures were used to investigate the mass of indigenous organic carbon in aquifer...
Dams, floodplain land use, and riparian forest conservation in the semiarid Upper Colorado River Basin, USA
D.C. Andersen, D.J. Cooper, K. Northcott
2007, Environmental Management (40) 453-475
Land and water resource development can independently eliminate riparian plant communities, including Fremont cottonwood forest (CF), a major contributor to ecosystem structure and functioning in semiarid portions of the American Southwest. We tested whether floodplain development was linked to river regulation in the Upper Colorado River Basin (UCRB) by relating...
Groundwater noble gas, age, and temperature signatures in an Alpine watershed: Valuable tools in conceptual model development
Andrew H. Manning, Jonathan S. Caine
2007, Water Resources Research (43)
Bedrock groundwater in alpine watersheds is poorly understood, mainly because of a scarcity of wells in alpine settings. Groundwater noble gas, age, and temperature data were collected from springs and wells with depths of 3–342 m in Handcart Gulch, an alpine watershed in Colorado. Temperature profiles indicate active groundwater circulation...
