Skip to main content
Advanced Search

Filters: Tags: Biogeochemistry (X)

131 results (85ms)   

Filters
Date Range
Extensions (Less)
Types (Less)
Contacts (Less)
Categories (Less)
Tag Types
Tag Schemes
View Results as: JSON ATOM CSV
thumbnail
In this study, we conducted rainfall simulation experiments in a cool desert ecosystem to examine the role of biological soil crust disturbance and composition on dissolved and sediment C and N losses. We compared runoff and sediment C and N losses from intact late-successional dark cyanolichen crusts (intact) to both trampled dark crusts (trampled) and dark crusts where the top 1 cm of the soil surface was removed (scraped). In a second experiment, we compared C and N losses in runoff and sediments in early-successional light cyanobacterial crusts (light) to that of intact late-successional dark cyanolichen crusts (dark). A relatively high rainfall intensity of approximately 38 mm per 10-min period was used to...
Most modeling studies on terrestrial feedbacks to warming over the twenty-first century imply that the net feedbacks are negative—that changes in ecosystems, on the whole, resist warming, largely through ecosystem carbon storage. Although it is clear that potentially important mechanisms can lead to carbon storage, a number of less well-understood mechanisms, several of which are rarely or incompletely modeled, tend to diminish the negative feedbacks or lead to positive feedbacks. At high latitudes, negative feedbacks from forest expansion are likely to be largely or completely compensated by positive feedbacks from decreased albedo, increased carbon emissions from thawed permafrost, and increased wildfire. At...
I conduct research on the transport and fate of organic contaminants in aquatic systems (terrestrial and marine). This entails field investigations and laboratory experiments that are designed to advance our understanding of natural processes and the effects of these processes on the behavior, mobility, and geochemical fate of organic chemicals of concern. I develop and apply new sampling and analytical techniques, identify potential molecular tracers, and develop models to predict contaminant fate. The laboratory I supervise houses analytical instrumentation that is used for detailed characterization of complex mixtures of organic chemicals as well as quantitative determination of targeted substances at ultra-trace...
In this study, we examined N gas loss as nitric oxide (NO) from N-fixing biologically crusted soils in Canyonlands National Park, Utah. We hypothesized that NO gas loss would increase with increasing N fixation potential of the biologically crusted soil. NO fluxes were measured from biologically crusted soils with three levels of N fixation potential (Scytonema-Nostoc-Collema spp. (dark)>Scytonema-Nostoc-Microcoleus spp. (medium)>Microcoleus spp. (light)) from soil cores and field chambers. In both cores and field chambers there was a significant effect of crust type on NO fluxes, but this was highly dependent on season. NO fluxes from field chambers increased with increasing N fixation potential of the biologically...
Although the variation in natural 15N abundance in plants and soils is well characterized, mechanisms controlling N isotopic composition of organic matter are still poorly understood. The primary goal of this study was to examine the role of NH3 volatilization from ungulate urine patches in determining 15N abundance in grassland plants and soil in Yellowstone National Park. We additionally used isotopic measurements to explore the pathways that plants in urine patches take up N. Plant, soil, and volatilized NH3d15N were measured on grassland plots for 10 days following the addition of simulated urine. Simulated urine increased 15N of roots and soil and reduced 15N of shoots. Soil enrichment was due to the volatilization...
thumbnail
Drainages are important features of semiarid landscapes because they are areas where surface water, groundwater, and terrestrial and aquatic ecosystems converge. Management of these critical ecohydrological systems requires a sound understanding of surface water-groundwater interactions. At the basin- to landscape-scale, drainage density, location, and channel characteristics are formed upon a geomorphic and geologic template that limit where and how surface water-groundwater interactions occur. At smaller scales, semiarid surface water-groundwater interactions exhibit a high degree of temporal and spatial variability that links directly to biogeochemical characteristics and ecosystem dynamics. In this paper, we...
thumbnail
This dataset includes the field measurements and laboratory analyses of surface water, seston, and sediment collected from Lake Powell, within Glen Canyon National Recreation area (GLCA), during high flow (May-June 2014) and low flow (August 2015) conditions. The study area includes 12-13 sampling sites that follow a transect spanning the entire length of the reservoir from the Colorado River inflow to the Glen Canyon dam, as well as the San Juan River arm, the Escalante River arm and West Canyon. Bed sediment samples were analyzed for mercury speciation, methylmercury production and degradation rates, total reduced sulfur, iron speciation, organic content, and 16S rRNA gene templates as a proxy for microbial abundances....
thumbnail
This data release supports publications on the Sleepers River Research Watershed near Danville, Vermont. Most of the research at Sleepers River takes place at W-9, the 40.5-hectare forested headwater site. Topics include understanding hydrologic flow paths, biogeochemical cycling, and organic carbon dynamics. Flow and precipitation data are integral to understanding these processes, for example by combining flow and chemical concentrations to compute solute export from the catchment. These records begin in late September 1991 and extend through calendar year 2018. The release includes five-minute data for discharge, daily data for precipitation, runoff,and maximum and minimum air temperature, and an annual tabulation...
thumbnail
This dataset includes mercury and other constituent concentration and physical properties data for surface sediment, pore water and surface water collected as part of the South San Francisco Bay Salt Pond Restoration Phase 1 (2010 to 2018) studies. The overarching focus of these studies was to monitor mercury (Hg) biogeochemistry in both sediment and water in response to management actions associated with the conversion of former salt producing ponds to contemporary wetland habitat. The two primary management actions included the breaching of Pond A6 during December 2010, and the construction and operation of an adjustable tidal control structure (TCS) associated with the Pond A5/A7/A8 Complex beginning in June...
thumbnail
This dataset includes shallow surface sediment (top 0–2 cm interval) constituent concentration data (primarily) and microbial methylmercury production potential rate data (limited) collected from the Cache Creek Settling Basin (CCSB), Yolo County, California, between April 2010 and July 2017. The dataset includes up to 706 observations (including field replicates) per sediment parameter, reflecting 93 unique sampling locations, with each location having been sampled from 1 to 28 times (excluding field replicates) over this 8-year period. There were four spatially intensive field campaigns conducted (February–March 2013, May 2013, October–November 2014, and January–March 2015), during which at least 90 sites were...
Recent increases in the atmospheric concentrations of carbon dioxide and methane have emphasized the need for a more complete understanding of the processes that control carbon transfer among air, land, and water. Knowledge of the amount, rate and chemical form of carbon transfer across environmental interfaces, such as the land-air and water-air interfaces, is of particular importance. These fluxes are commonly controlled by a combination of physical, biological, and chemical processes at or near the interface. Isolation of the primary mechanisms that determine carbon transfer across the interface allows for development of process-based models that can be used for carbon mass transfer estimates at the ecosystem...
The present chapter focuses on the laboratory and field experiments that are used to quantify rates of biogeochemical processes and develop conceptual models of the role of bacteria in the carbon and energy flow in subsurface environments. Several integrated studies are presented that used multidisciplinary approach to examine the evolution of groundwater ecosystems. Because of the increasing i...
thumbnail
The exotic annual grass Bromus tectorum has replaced thousands of hectares of native perennial vegetation in semi-arid ecosystems of the western United States. Inorganic N availability and production were compared in soil from monodominant patches of Bromus tectorum, the perennial bunchgrass Elymus elymoides, and the shrub Artemisia tridentata, in Curlew Valley, a salt-desert shrub site in Northern Utah. Bromus-dominated soil had greater %N in the top 10 cm than Artemisia or Elymus-dominated soils. As determined by spring isotope-dilution assays, gross mineralization and nitrification rates were higher in Bromus-dominated than Artemisia-dominated soils, but gross rates of NH4+ and NO3- consumption were also higher....
Geochemical mass balances were computed for water years 1992–1997 (October 1991 through September 1997) for the five watersheds of the U.S. Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) Program to determine the primary regional controls on yields of the major dissolved inorganic solutes. The sites, which vary markedly with respect to climate, geology, physiography, and ecology, are: Allequash Creek, Wisconsin (low-relief, humid continental forest); Andrews Creek, Colorado (cold alpine, taiga/tundra, and subalpine boreal forest); Río Icacos, Puerto Rico (lower montane, wet tropical forest); Panola Mountain, Georgia (humid subtropical piedmont forest); and Sleepers River, Vermont (humid northern...
thumbnail
The dataset documents the spatial and temporal variability of nutrients and related water quality parameters at high spatial resolution in the North Delta of the Sacramento-San Joaquin River Delta of California, USA. The dataset includes surface mapping, depth profile, and discrete data for nitrate, ammonium, phosphate, dissolved organic carbon, temperature, conductivity, dissolved oxygen, and chlorophyll as well as information about phytoplankton community composition. Data-collection cruises were conducted over two time periods in July and October 2018 across two flooded islands with dense submerged aquatic vegetation beds. Little Hastings Tract received an herbicide treatment by the California Department of Boating...
thumbnail
This dataset includes mercury and other constituent concentration and physical properties data for seven deep sediment profiles (ranging from 79 cm to 214 cm in length) collected from the thalwag of Alviso Slough, a major tributary to South San Francisco Bay (California, USA). Field sampling occurred during May 2012 (4 sites) and January 2016 (3 sites). Each profile was comprised of 1–4 core sub-sections, which were collected from adjacent boreholes with 10–18 cm of vertical overlap. This data product includes two data tables (*.csv): 1) ‘T1_ALSL_DC_Sed_Data.csv’, the deep core analytical results; 2) ‘T2_ALSL_DC_QA_Data.csv’, quality assurance data. The two image files, ‘ALSL_DC_Log_2012.pdf’ and ‘ALSL-DC_Log_2016.pdf’,...
thumbnail
The geospatial data presented here as ArcGIS layers denote landcover/landuse classifications to support field sampling efforts that occurred within the Cache Creek Settling Basin (CCSB) from 2010-2019. Manual photointerpretation of a National Agriculture Imagery Program (NAIP) dataset collected in 2012 was used to characterize landcover/landuse categories (hereafter habitat classes). Initially 9 categories were assigned based on vegetation structure (Vegtype1). These were then parsed into two levels of habitat classes that were chosen for their representativeness and use for statistical analyses of field sampling. At the coarsest level (Landcover 1), five habitat classes were assigned: Agriculture, Riparian,...
This project seeks to quantify, predict, and project the relative role of plant physiology, among other ecosystem drivers, on carbon, nutrient, and trace-metal biogeochemistry. Approaches span landscape-to-molecular scales as necessary to understand how human and stochastic alterations of wetland structure influence wetland function. Research sites represent a wide range of salinity and management conditions, from rice agriculture to coastal and restored wetlands. Primary goals include evaluating management and modeling approaches to quantify wetland carbon sequestration, greenhouse gas budgets and/or mercury methylation and export.
thumbnail
IMPORTANT NOTE: Data and supporting information from samples collected during 2015-16 can be can be accessed from this link. The U.S. Geological Survey is studying Lake Koocanusa, a border reservoir between British Columbia in Canada and Montana, in collaboration with the Montana Department of Environmental Quality and the U.S. Environmental Protection Agency (Region 8). This work is part of a multi-agency project to apply an ecosystem-scale selenium modeling methodology (Presser and Luoma, 2010) to the lake to support development of site-specific selenium guidelines for the protection of aquatic life. A conceptual model framework was published in 2017 (Jenni, Naftz, and Presser, 2017) to serve as a coherent and...
map background search result map search result map Surface water-groundwater interactions in semiarid drainages of the American southwest Impacts of Biological Soil Crust Disturbance and Composition on C and N Loss from Water Erosion Inorganic N turnover and availability in annual- and perennial-dominated soils in a northern Utah shrub-steppe ecosystem Cottonwood Lake Study Area - Water Chemistry - Wetlands Data for Biogeochemical and Physical Processes Controlling Mercury Methylation and Bioaccumulation in Lake Powell, Glen Canyon National Recreation Area, Utah and Arizona, 2014-2015 Mercury speciation and other constituent data from deep sediment cores in Alviso Slough, South San Francisco Bay, California, 2012-16 Shallow Sediment Geochemical Data for the Cache Creek Settling Basin, Yolo County, California, 2010–17 USGS Measurements of Dissolved and Suspended Particulate Material Selenium in Lake Koocanusa in the Vicinity of Libby Dam (MT), 2015-2017 (update) Five-minute discharge; daily precipitation, stream runoff, and maximum and minimum air temperature; and annual precipitation and runoff for W-9 catchment, Sleepers River Research Watershed near Danville, Vermont, 1991-2018 Mercury speciation and other constituent data for surface sediment and water associated with the South San Francisco Bay Salt Pond Restoration, 2010-18 High-Resolution Measurements to Identify Effects of Aquatic Vegetation on Water Quality and Stratification Habitat Maps for the Cache Creek Settling Basin, Yolo County, California Cottonwood Lake Study Area - Water Chemistry - Wetlands Five-minute discharge; daily precipitation, stream runoff, and maximum and minimum air temperature; and annual precipitation and runoff for W-9 catchment, Sleepers River Research Watershed near Danville, Vermont, 1991-2018 Mercury speciation and other constituent data from deep sediment cores in Alviso Slough, South San Francisco Bay, California, 2012-16 Habitat Maps for the Cache Creek Settling Basin, Yolo County, California Shallow Sediment Geochemical Data for the Cache Creek Settling Basin, Yolo County, California, 2010–17 Mercury speciation and other constituent data for surface sediment and water associated with the South San Francisco Bay Salt Pond Restoration, 2010-18 High-Resolution Measurements to Identify Effects of Aquatic Vegetation on Water Quality and Stratification USGS Measurements of Dissolved and Suspended Particulate Material Selenium in Lake Koocanusa in the Vicinity of Libby Dam (MT), 2015-2017 (update) Impacts of Biological Soil Crust Disturbance and Composition on C and N Loss from Water Erosion Data for Biogeochemical and Physical Processes Controlling Mercury Methylation and Bioaccumulation in Lake Powell, Glen Canyon National Recreation Area, Utah and Arizona, 2014-2015 Inorganic N turnover and availability in annual- and perennial-dominated soils in a northern Utah shrub-steppe ecosystem Surface water-groundwater interactions in semiarid drainages of the American southwest