A critical review of three methods used for the measurement of mercury (Hg2+)-dissolved organic matter stability constants
J. D. Gasper, George R. Aiken, Joseph N. Ryan
2007, Applied Geochemistry (22) 1583-1597
Three experimental techniques - ion exchange, liquid-liquid extraction with competitive ligand exchange, and solid-phase extraction with competitive ligand exchange (CLE-SPE) - were evaluated as methods for determining conditional stability constants (K) for the binding of mercury (Hg2+) to dissolved organic matter (DOM). To determine the utility of a given method...
Rainfall limit of the N cycle on Earth
Stephanie A. Ewing, Greg Michalski, Mark Thiemens, R.C. Quinn, J. L. Macalady, S. Kohl, Scott D. Wankel, Carol Kendall, Christopher P McKay, Ronald Amundson
2007, Global Biogeochemical Cycles (21)
In most climates on Earth, biological processes control soil N. In the Atacama Desert of Chile, aridity severely limits biology, and soils accumulate atmospheric NO3−. We examined this apparent transformation of the soil N cycle using a series of ancient Atacama Desert soils (>2 My) that vary in rainfall (21...
Tree and stand transpiration in a Midwestern bur oak savanna after elm encroachment and restoration thinning
H. Asbjornsen, M.D. Tomer, M. Gomez-Cardenas, L.A. Brudvig, C.M. Greenan, K. Schilling
2007, Forest Ecology and Management (247) 209-219
Oak savannas, once common in the Midwest, are now isolated remnants within agricultural landscapes. Savanna remnants are frequently encroached by invasive trees to become woodlands. Thinning and prescribed burning can restore savanna structure, but the ecohydrological effects of managing these remnants are poorly understood. In this study, we measured sap...
Three-dimensional flow in the Florida platform: Theoretical analysis of Kohout convection at its type locality
J.D. Hughes, H. Leonard Vacher, Ward E. Sanford
2007, Geology (35) 663-666
Kohout convection is the name given to the circulation of saline groundwater deep within carbonate platforms, first proposed by F.A. Kohout in the 1960s for south Florida. It is now seen as an Mg pump for dolomitization by seawater. As proposed by Kohout, cold seawater is drawn into the Florida...
Discontinuities in stream nutrient uptake below lakes in mountain drainage networks
C.D. Arp, M. A. Baker
2007, Limnology and Oceanography (52) 1978-1990
In many watersheds, lakes and streams are hydrologically linked in spatial patterns that influence material transport and retention. We hypothesized that lakes affect stream nutrient cycling via modifications to stream hydrogeomorphology, source-waters, and biological communities. We tested this hypothesis in a lake district of the Sawtooth Mountains, Idaho. Uptake of...
Input, flux, and persistence of six select pesticides in San Francisco Bay
Kathryn Kuivila, B.E. Jennings
2007, International Journal of Environmental Analytical Chemistry (87) 897-911
Temporal patterns of pesticide inputs to San Francisco Bay were identified and correlated with timing of application and transport mechanism. Fluxes were calculated from measured concentrations and estimated flow. Persistence of the pesticides under typical riverine or estuarine conditions were estimated from laboratory experiments. Simazine was detected most frequently and...
Dissolved organic carbon in Alaskan boreal forest: Sources, chemical characteristics, and biodegradability
Kimberly P. Wickland, Jason C. Neff, George R. Aiken
2007, Ecosystems (10) 1323-1340
The fate of terrestrially-derived dissolved organic carbon (DOC) is important to carbon (C) cycling in both terrestrial and aquatic environments, and recent evidence suggests that climate warming is influencing DOC dynamics in northern ecosystems. To understand what determines the fate of terrestrial DOC, it is essential to quantify the chemical...
Cloud water in windward and leeward mountain forests: The stable isotope signature of orographic cloud water
M. A. Scholl, T. W. Giambelluca, S. B. Gingerich, M.A. Nullet, L.L. Loope
2007, Water Resources Research (43)
Cloud water can be a significant hydrologic input to mountain forests. Because it is a precipitation source that is vulnerable to climate change, it is important to quantify amounts of cloud water input at watershed and regional scales. During this study, cloud water and rain samples were collected monthly for...
Hydrology and subsurface transport of oil-field brine at the U.S. Geological Survey OSPER site "A", Osage County, Oklahoma
William N. Herkelrath, Yousif K. Kharaka, James J. Thordsen, Marvin M. Abbott
2007, Applied Geochemistry (22) 2155-2163
Spillage and improper disposal of saline produced water from oil wells has caused environmental damage at thousands of sites in the United States. In order to improve understanding of the fate and transport of contaminants at these sites, the U.S. Geological...
Sources and transport of algae and nutrients in a Californian river in a semi-arid climate
Nobuhito Ohte, Randy A. Dahlgren, Steven R. Silva, Carol Kendall, Charles R. Kratzer, Daniel H. Doctor
2007, Freshwater Biology (52) 2476-2493
1. To elucidate factors contributing to dissolved oxygen (DO) depletion in the Stockton Deep Water Ship Channel in the lower San Joaquin River, spatial and temporal changes in algae and nutrient concentrations were investigated in relation to flow regime under the semiarid climate conditions. 2. Chlorophyll-a (chl-a) concentration and loads...
Centimeter-scale characterization of biogeochemical gradients at a wetland-aquifer interface using capillary electrophoresis
S. Baez-Cazull, J.T. McGuire, Isabelle M. Cozzarelli, A. Raymond, L. Welsh
2007, Applied Geochemistry (22) 2664-2683
Steep biogeochemical gradients were measured at mixing interfaces in a wetland-aquifer system impacted by landfill leachate in Norman, Oklahoma. The system lies within a reworked alluvial plain and is characterized by layered low hydraulic conductivity wetland sediments interbedded with sandy aquifer material. Using cm-scale passive diffusion samplers, "peepers", water samples...
Local structuring factors of invertebrate communities in ephemeral freshwater rock pools and the influence of more permanent water bodies in the region
M. Jocque, T. Graham, L. Brendonck
2007, Hydrobiologia (592) 271-280
We used three isolated clusters of small ephemeral rock pools on a sandstone flat in Utah to test the importance of local structuring processes on aquatic invertebrate communities. In the three clusters we characterized all ephemeral rock pools (total: 27) for their morphometry, and monitored their water quality, hydrology and...
Mode of occurrence and environmental mobility of oil-field radioactive material at US Geological Survey research site B, Osage-Skiatook Project, northeastern Oklahoma
Robert A. Zielinski, James R. Budahn
2007, Applied Geochemistry (22) 2125-2137
Two samples of produced-water collected from a storage tank at US Geological Survey research site B, near Skiatook Lake in northeastern Oklahoma, have activity concentrations of dissolved 226Ra and 228Ra that are about 1500 disintegrations/min/L (dpm/L). Produced-water also contains minor amounts of small (5–50 μm) suspended grains of Ra-bearing BaSO4 (barite). Precipitation of radioactive...
Evaluation of sulfate reduction at experimentally induced mixing interfaces using small-scale push-pull tests in an aquifer-wetland system
T.A. Kneeshaw, Jennifer T. McGuire, Erik W. Smith, Isabelle M. Cozzarelli
2007, Applied Geochemistry (22) 2618-2629
This paper presents small-scale push–pull tests designed to evaluate the kinetic controls on SO42-">SO42- reduction in situ at mixing interfaces between a wetland and aquifer impacted by landfill leachate at the Norman Landfill research site, Norman, OK. Quantifying the...
A cold phase of the East Pacific triggers new phytoplankton blooms in San Francisco Bay
James E. Cloern, Alan D. Jassby, Janet K. Thompson, Kathryn Hieb
2007, Proceedings of the National Academy of Sciences of the United States of America (104) 18561-18565
Ecological observations sustained over decades often reveal abrupt changes in biological communities that signal altered ecosystem states. We report a large shift in the biological communities of San Francisco Bay, first detected as increasing phytoplankton biomass and occurrences of new seasonal blooms that began in 1999. This phytoplankton increase is...
Diurnal variability in riverine dissolved organic matter composition determined by in situ optical measurement in the San Joaquin River (California, USA)
R.G.M. Spencer, B.A. Pellerin, B.A. Bergamaschi, B.D. Downing, T.E.C. Kraus, D.R. Smart, R.A. Dahlgren, P.J. Hernes
2007, Hydrological Processes (21) 3181-3189
Dissolved organic matter (DOM) concentration and composition in riverine and stream systems are known to vary with hydrological and productivity cycles over the annual and interannual time scales. Rivers are commonly perceived as homogeneous with respect to DOM concentration and composition, particularly under steady flow conditions over short time periods....
Investigation of the groundwater system at Masaya Caldera, Nicaragua, using transient electromagnetics and numerical simulation
R.E. MacNeil, W. E. Sanford, C.B. Connor, S.K. Sandberg, M. Diez
2007, Journal of Volcanology and Geothermal Research (166) 217-232
The distribution of groundwater beneath Masaya Volcano, in Nicaragua, and its surrounding caldera was characterized using the transient electromagnetic method (TEM). Multiple soundings were conducted at 30 sites. Models of the TEM data consistently indicate a resistive layer that is underlain by one or more conductive layers. These two layers...
Cleats and their relation to geologic lineaments and coalbed methane potential in Pennsylvanian coals in Indiana
W. Solano-Acosta, Maria Mastalerz, A. Schimmelmann
2007, International Journal of Coal Geology (72) 187-208
Cleats and fractures in Pennsylvanian coals in southwestern Indiana were described, statistically analyzed, and subsequently interpreted in terms of their origin, relation to geologic lineaments, and significance for coal permeability and coalbed gas generation and storage. These cleats can be interpreted as the result of superimposed endogenic and exogenic processes....
Influence of in-stream diel concentration cycles of dissolved trace metals on acute toxicity to one-year-old cutthroat trout (Oncorhynchus clarki lewisi)
David A. Nimick, David D. Harper, Aida Farag, Tom Cleasby, Elizabeth MacConnell, D. Skaar
2007, Environmental Toxicology and Chemistry (26) 2667-2678
Extrapolating results of laboratory bioassays to streams is difficult, because conditions such as temperature and dissolved metal concentrations can change substantially on diel time scales. Field bioassays conducted for 96 h in two mining‐affected streams compared the survival of hatchery‐raised, metal‐näive westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to dissolved...
Physically based estimation of soil water retention from textural data: General framework, new models, and streamlined existing models
John R. Nimmo, William N. Herkelrath, Luna Laguna
2007, Vadose Zone Journal (6) 766-773
Numerous models are in widespread use for the estimation of soil water retention from more easily measured textural data. Improved models are needed for better prediction and wider applicability. We developed a basic framework from which new and existing models can be derived to facilitate improvements. Starting from the assumption...
Influence of groundwater pumping on streamflow restoration following upstream dam removal
James E. Constantz, Hedeff I. Essaid
2007, Hydrological Processes (21) 2823-2834
We compared streamflow in basins under the combined impacts of an upland dam and groundwater pumping withdrawals, by examining streamflow in the presence and absence of each impact. As a qualitative analysis, inter-watershed streamflow comparisons were performed for several rivers flowing into the east side...
Ordination of breeding birds in relation to environmental gradients in three southeastern United States floodplain forests
J.S. Wakeley, M.P. Guilfoyle, T. J. Antrobus, R.A. Fischer, W.C. Barrow Jr., P.B. Hamel
2007, Wetlands Ecology and Management (15) 417-439
We used an ordination approach to identify factors important to the organization of breeding bird communities in three floodplains: Cache River, Arkansas (AR), Iatt Creek, Louisiana (LA), and the Coosawhatchie River, South Carolina (SC), USA. We used 5-min point counts to sample birds in each study area each spring from...
Ammonia-oxidizing bacterial community composition in estuarine and oceanic environments assessed using a functional gene microarray
B.B. Ward, D. Eveillard, Julie D. Kirshtein, J.D. Nelson, Mary A. Voytek, G. A. Jackson
2007, Environmental Microbiology (9) 2522-2538
The relationship between environmental factors and functional gene diversity of ammonia-oxidizing bacteria (AOB) was investigated across a transect from the freshwater portions of the Chesapeake Bay and Choptank River out into the Sargasso Sea. Oligonucleotide probes (70-bp) designed to represent the diversity of ammonia monooxygenase (amoA) genes from Chesapeake Bay...
Development of a mercury speciation, fate, and biotic uptake (BIOTRANSPEC) model: Application to Lahontan Reservoir (Nevada, USA)
N. Gandhi, S.P. Bhavsar, M.L. Diamond, James S. Kuwabara, Mark C. Marvin-DePasquale, David P. Krabbenhoft
2007, Environmental Toxicology and Chemistry (26) 2260-2273
A mathematically linked mercury transport, speciation, kinetic, and simple biotic uptake (BIOTRANSPEC) model has been developed. An extension of the metal transport and speciation (TRANSPEC) model, BIOTRANSPEC estimates the fate and biotic uptake of inorganic (Hg(II)), elemental (Hg(0)) and organic (MeHg) forms of mercury and their species in the dissolved,...
Formation and disruption of aquifers in southwestern Chryse Planitia, Mars
J.A.P. Rodriguez, K. L. Tanaka, J.S. Kargel, J. M. Dohm, R. Kuzmin, A.G. Fairen, S. Sasaki, G. Komatsu, D. Schulze-Makuch, Y. Jianguo
2007, Icarus (191) 545-567
We present geologic evidence suggesting that after the development of Mars' cryolithosphere, the formation of aquifers in southwestern Chryse Planitia and their subsequent disruption led to extensive regional resurfacing during the Late Hesperian, and perhaps even during the Amazonian. In our model, these aquifers formed preferentially along thrust faults associated...
