Manganese-enhanced magnetic resonance microscopy of mineralization
I.E. Chesnick, T.I. Todorov, J.A. Centeno, D.E. Newbury, Justin R. Small, K. Potter
2007, Magnetic Resonance Imaging (25) 1095-1104
Paramagnetic manganese (II) can be employed as a calcium surrogate to sensitize magnetic resonance microscopy (MRM) to the processing of calcium during bone formation. At high doses, osteoblasts can take up sufficient quantities of manganese, resulting in marked changes in water proton T1, T2 and magnetization transfer ratio values compared...
Factors influencing ground-water recharge in the eastern United States
B. T. Nolan, R. W. Healy, P.E. Taber, K. Perkins, K.J. Hitt, D.M. Wolock
2007, Journal of Hydrology (332) 187-205
Ground-water recharge estimates for selected locations in the eastern half of the United States were obtained by Darcian and chloride-tracer methods and compared using statistical analyses. Recharge estimates derived from unsaturated-zone (RUZC) and saturated-zone (RSZC) chloride mass balance methods are less variable (interquartile ranges or IQRs are 9.5 and 16.1...
The geochemistry of pesticides
Jack E. Barbash
2007, Book chapter, Treatise on geochemistry
The mid-1970s marked a major turning point in human history, for it was at that moment that the ability of the Earth’s ecosystems to absorb most of the biological impacts of human activities appears to have been exceeded by the magnitude of those impacts. This conclusion is based partly upon...
Effects of habitat management treatments on plant community composition and biomass in a Montane wetland
Jane E. Austin, Janet R. Keough, W.H. Pyle
2007, Wetlands (27) 570-587
Grazing and burning are commonly applied practices that can impact the diversity and biomass of wetland plant communities. We evaluated the vegetative response of wetlands and adjacent upland grasslands to four treatment regimes (continuous idle, fall prescribed burning followed by idle, annual fall cattle grazing, and rotation of summer grazing...
A simple pore water hydrogen diffusion syringe sampler
Don Vroblesky, Francis H. Chapelle, Paul M. Bradley
2007, Ground Water (45) 798-802
Molecular hydrogen (H2) is an important intermediate product and electron donor in microbial metabolism. Concentrations of dissolved H 2 are often diagnostic of the predominant terminal electron-accepting processes in ground water systems or aquatic sediments. H2 concentrations are routinely measured in ground water monitoring wells but are rarely measured in...
Evaluation of a non-point source pollution model, AnnAGNPS, in a tropical watershed
V. Polyakov, A. Fares, D. Kubo, J. Jacobi, C. Smith
2007, Environmental Modelling and Software (22) 1617-1627
Impaired water quality caused by human activity and the spread of invasive plant and animal species has been identified as a major factor of degradation of coastal ecosystems in the tropics. The main goal of this study was to evaluate the performance of AnnAGNPS (Annualized Non-Point Source Pollution Model), in...
Bottom sediments and pore waters near a hydrothermal vent in Lake Baikal (Frolikha Bay)
L.Z. Granina, J. Klerkx, E. Callender, M. Leermakers, L.P. Golobokova
2007, Russian Geology and Geophysics (48) 237-246
We discuss the redox environments and the compositions of bottom sediments and sedimentary pore waters in the region of a hydrothermal vent in Frolikha Bay, Lake Baikal. According to our results, the submarine vent and its companion nearby spring on land originate from a common source. The most convincing evidence...
Interaction and influence of two creeks on Escherichia coli concentrations of nearby beaches: Exploration of predictability and mechanisms
M.B. Nevers, R.L. Whitman, W.E. Frick, Z. Ge
2007, Journal of Environmental Quality (36) 1338-1345
The impact of river outfalls on beach water quality depends on numerous interacting factors. The delivery of contaminants by multiple creeks greatly complicates understanding of the source contributions, especially when pollution might originate up- or down-coast of beaches. We studied two beaches along Lake Michigan that are located between two...
Aquatic vertebrate assemblages of the upper Clear Creek Watershed, California
L. R. Brown, J. T. May
2007, Western North American Naturalist (67) 439-451
We sampled streams in the Upper Clear Creek Watershed in northwestern California in fall 2004 and fall 2005 to document assemblages of aquatic vertebrates and to provide resource managers with information on the importance of these assemblages in terms of regional biodiversity. We used single-pass backpack electrofishing to sample 15...
An evaluation of petrogenic hydrocarbons in northern Gulf of Alaska continental shelf sediments - The role of coastal oil seep inputs
J.W. Short, J.J. Kolak, J. R. Payne, G. K. Van Kooten
2007, Organic Geochemistry (38) 643-670
We compared hydrocarbons in water, suspended particulate matter (SPM), and riparian sediment collected from coastal watersheds along the Yakataga foreland with corresponding hydrocarbons in Gulf of Alaska benthic sediments. This comparison allows an evaluation of hydrocarbon contributions to marine sediments from natural oil seeps, coal and organic matter (e.g., kerogen)...
Cryovolcanic features on Titan's surface as revealed by the Cassini Titan Radar Mapper
Rosaly Lopes, K. L. Mitchell, Ellen R. Stofan, Jonathan I. Lunine, Ralf D. Lorenz, F. Paganelli, Randolph L. Kirk, C. A. Wood, Stephen D. Wall, L.E. Robshaw, A.D. Fortes, Catherine D. Neish, Jani Radebaugh, E. Reffet, S.J. Ostro, Charles Elachi, M.D. Allison, Y. Anderson, R. Boehmer, G. Boubin, Philip S. Callahan, P. Encrenaz, E. Flamini, G. Francescetti, Y. Gim, G. Hamilton, S. Hensley, Michael A. Janssen, W.T.K. Johnson, K. Kelleher, D.O. Muhleman, G. Ori, R. Orosei, G. Picardi, F. Posa, L.E. Roth, R. Seu, S. Shaffer, Laurence A. Soderblom, B. Stiles, S. Vetrella, R.D. West, L. Wye, H. A. Zebker
2007, Icarus (186) 395-412
The Cassini Titan Radar Mapper obtained Synthetic Aperture Radar images of Titan's surface during four fly-bys during the mission's first year. These images show that Titan's surface is very complex geologically, showing evidence of major planetary geologic processes, including cryovolcanism. This paper discusses the variety of cryovolcanic features identified from...
DIN retention-transport through four hydrologically connected zones in a headwater catchment of the Upper Mississippi River
F.J. Triska, J.H. Duff, R.W. Sheibley, A. P. Jackman, R.J. Avanzino
2007, Journal of the American Water Resources Association (43) 60-71
Dissolved inorganic nitrogen (DIN) retention-transport through a headwater catchment was synthesized from studies encompassing four distinct hydrologic zones of the Shingobee River Headwaters near the origin of the Mississippi River. The hydrologic zones included: (1) hillslope ground water (ridge to bankside riparian); (2) alluvial...
Late quaternary temperature record from buried soils of the North American Great Plains
L. Nordt, J. Von Fischer, L. Tieszen
2007, Geology (35) 159-162
We present the first comprehensive late Quaternary record of North American Great Plains temperature by assessing the behavior of the stable isotopic composition (δ13C) of buried soils. After examining the relationship between the δ13C of topsoil organic matter and July temperature from 61 native prairies within a latitudinal range of...
Stream ecosystem response to limestone treatment in acid impacted watersheds of the allegheny plateau
S.E. McClurg, J.T. Petty, P. M. Mazik, J.L. Clayton
2007, Ecological Applications (17) 1087-1104
Restoration programs are expanding worldwide, but assessments of restoration effectiveness are rare. The objectives of our study were to assess current acid-precipitation remediation programs in streams of the Allegheny Plateau ecoregion of West Virginia (USA), identify specific attributes that could and could not be fully restored, and quantify temporal trends...
Apparent climatically induced increase of tree mortality rates in a temperate forest
P. J. van Mantgem, N.L. Stephenson
2007, Ecology Letters (10) 909-916
We provide a first detailed analysis of long-term, annual-resolution demographic trends in a temperate forest. After tracking the fates of 21 338 trees in a network of old-growth forest plots in the Sierra Nevada of California, we found that mortality rate, but not the recruitment rate, increased significantly over the...
Evidence of lake whitefish spawning in the Detroit River: Implications for habitat and population recovery
E.F. Roseman, G.W. Kennedy, J. Boase, B.A. Manny, T. N. Todd, W. Stott
2007, Journal of Great Lakes Research (33) 397-406
Historic reports imply that the lower Detroit River was once a prolific spawning area for lake whitefish (Coregonus clupeaformis) prior to the construction of the Livingstone shipping channel in 1911. Large numbers of lake whitefish migrated into the river in fall where they spawned on expansive limestone bedrock and gravel...
A new comprehensive approach to characterizing carbonaceous aerosol with an application to wintertime Fresno, California PM2.5
P. Herckes, J.A. Leenheer, J.L. Collett Jr.
2007, Atmospheric Chemistry and Physics Discussions (7) 8423-8453
Fine particulate matter (PM2.5) samples were collected during a three week winter period in Fresno (CA). A composite sample was characterized by isolating several distinct fractions and characterizing them by infrared and nuclear magnetic resonance (NMR) spectroscopy. More than 80% of the organic matter in the aerosol samples was recovered...
Variable role of aquatic macroinvertebrates in initial breakdown of seasonal leaf litter inputs to a cold-desert river
S. M. Nelson, D.C. Andersen
2007, Southwestern Naturalist (52) 219-228
We used coarse-mesh and fine-mesh leafpacks to examine the importance of aquatic macroinvertebrates in the breakdown of floodplain tree leaf litter that seasonally entered a sand-bedded reach of the sixth-order Yampa River in semiarid Colorado. Leafpacks were positioned off the easily mobilized channel bed, mimicking litter trapped in debris piles....
Structure and composition of a watershed-scale sediment information network
W. R. Osterkamp, J. R. Gray, J.B. Laronne, J.R. Martin
2007, International Journal of Sediment Research (22) 238-246
A 'Watershed-Scale Sediment Information Network' (WaSSIN), designed to complement UNESCO's International Sedimentation Initiative, was endorsed as an initial project by the World Association for Sedimentation and Erosion Research. WaSSIN is to address global fluvial-sediment information needs through a network approach based on consistent protocols for the collection, analysis, and storage...
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...
Anguilliform larvae collected off North Carolina
Steve W. Ross, T.L. Casazza, A.M. Quattrini, K. J. Sulak
2007, Marine Biology (150) 681-695
The distinctive larval stage of eels (leptocephalus) facilitates dispersal through prolonged life in the open ocean. Leptocephali are abundant and diverse off North Carolina, yet data on distributions and biology are lacking. The water column (from surface to 1,293 m) was sampled in or near the Gulf Stream off Cape...
Fracture control of ground water flow and water chemistry in a rock aquitard
T.T. Eaton, Marilyn P. Anderson, K. R. Bradbury
2007, Ground Water (45) 601-615
There are few studies on the hydrogeology of sedimentary rock aquitards although they are important controls in regional ground water flow systems. We formulate and test a three-dimensional (3D) conceptual model of ground water flow and hydrochemistry in a fractured sedimentary rock aquitard to show that flow dynamics within the...
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,...
Imprint of oaks on nitrogen availability and δ15N in California grassland-savanna: A case of enhanced N inputs?
S.S. Perakis, C.H. Kellogg
2007, Plant Ecology (191) 209-220
Woody vegetation is distributed patchily in many arid and semi-arid ecosystems, where it is often associated with elevated nitrogen (N) pools and availability in islands of fertility. We measured N availability and δ15N in paired blue-oak versus annual grass dominated patches to characterize the causes and consequences of spatial variation...
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...
