Filters: Tags: Biogeochemistry (X)
131 results (268ms)|
Filters
Date Range
Extensions Types Contacts
Categories Tag Types
|
IMPORTANT NOTE: An updated version that contains data from samples collected during 2017 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 a site-specific selenium guideline for the protection of aquatic life. This Data Release makes available measurements taken during the periods of May, 2015 to October, 2015 and April,...
Categories: Data;
Types: Citation;
Tags: Lake Koocanusa,
Libby Dam, Lincoln County, Montana,
USGS Science Data Catalog (SDC),
biogeochemistry,
selenium
The Integrated Watershed Studies Team is a multidisciplinary group of scientists who carry out collaborative investigations of water chemistry at varying spatial scales. The team integrates physical, chemical, and biological data by applying models and spatial geographic data to quantify the role of hydrological and biogeochemical processes on the chemical evolution of surface water and groundwater. This group is part of the National Water Quality Assessment Project of the U.S. Geological Survey.
A survey of nitric oxide (NO) emission from Chihuahuan desert soils found mean NO fluxes <0.1 ng NO-N cm-2 h-1 during the dry season. These fluxes were at the lower end of the range reported for temperate grassland and woodland ecosystems. NO fluxes from wet or watered soils were higher (0.1-35 ng NO-N cm-2 h-1 ). Watering of black grama grassland soils produced an initial pulse of 12 ng cm-2 h-1 (12-h after 1-cm watering) with high fluxes sustained over 4 days with repeated watering. Initial pulses from shrubland soils were lower (maximum 5 ng cm-2 h-1 ), and fluxes declined with repeated watering. Repeated watering of creosotebush soils depleted the soil NH4 + pool, and NO emissions were directly related to soil...
Whole air drawn from four heights within the high elevation (3,340 m asl), deep, winter snowpack at Niwot Ridge, Colorado, were sampled into stainless steel canisters, and subsequently analyzed by gas chromatography for 51 volatile inorganic and organic gases. Two adjacent plots with similar snow cover were sampled, one over bare soil and a second one from within a snow-filled chamber where Tedlar/Teflon-film covered the ground and isolated it from the soil. This comparison allowed for studying effects from processes in the snowpack itself versus soil influences on the gas concentrations and fluxes within and through the snowpack. Samples were also collected from ambient air above the snow surface for comparison...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Biogeochemistry,
CFC,
Fluxes,
HCFC,
Hydrocarbons,
<p>The overall objective of my research is to understand the movement and quality of surface and groundwater using geochemical approaches. Some key issues that are considered in this research are the environmental aspects of energy and mineral resources, climate change, and carbon cycling and sequestration. The geochemical approaches that are used in this research include the use of isotopic tracers, trace elements, and radioisotopes. My research has focused on the sampling and analysis of produced waters from geologic carbon sequestration studies, geochemical characterization of sediment transport in the coastal zone, the environmental chemistry of mercury in coastal regions, and water quality analysis for samples...
General objectives are to 1) add to the fundamental understanding of Se biogeochemistry; 2) document Se sources and assess the environmental impacts of Se contamination; 3) construct and validate an ecosystem-scale Se methodology that connects dissolved Se to bioaccumulated Se within an occurrence of Se exposure; and 4) develop scenarios to illustrate ecosystem foodwebs and hydrologic settings that control Se exposure within a watershed or site as an ecologically consistent management approach for Se. Within that framework, the specific objectives are to 1) quantitatively apply ecosystem-scale Se modeling on a site-specific basis in support of fish and wildlife management or protection through collaboration with...
We examined the 10-day response of soil microbial biomass-N to additions of carbon (dextrose) and nitrogen (NH4NO3) to water-amended soils in a factorial experiment in four plant communities of the Chihuahuan desert of New Mexico (U.S.A.). In each site, microbial biomass-N and soil carbohydrates increased and extractable soil N decreased in response to watering alone. Fertilization with N increased microbial biomass-N in grassland soils; whereas, fertilization with C increased microbial biomass-N and decreased extractable N and P in all communities dominated by shrubs, which have invaded large areas of grassland in the Chihuahuan desert during the last 100 years. Our results support the hypothesis that the control...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Biogeochemistry,
Springer,
desert soils,
desertification,
soil carbon,
The objectives of my work are to better understand nutrient sources and cycling in specific environments to aid in resource management and pollution abatement and to improve and develop isotopic analytical methodologies.
Strontium isotope sourcing has become a common and useful method for assigning sources to archaeological artifacts. In Chaco Canyon, an Ancestral Pueblo regional center in New Mexico, previous studies using these methods have suggested that significant portion of maize and wood originate in the Chuska Mountains region, 75 km to the East. In the present manuscript, these results were tested using both frequentist methods (to determine if geochemical sources can truly be differentiated) and Bayesian methods (to address uncertainty in geochemical source attribution). It was found that Chaco Canyon and the Chuska Mountain region are not easily distinguishable based on radiogenic strontium isotope values. The strontium...
Categories: Publication;
Types: Citation;
Tags: Agriculture,
Anthropology,
Archaeology,
Archaeometry,
Atoms,
This data release documents the spatial and temporal variability of nutrients and related water quality parameters at high spatial resolution in the Sacramento-San Joaquin River Delta of California, USA. The data set includes nitrate, ammonium, phosphate, dissolved organic carbon, temperature, conductivity, dissolved oxygen, turbidity, and chlorophyll. Data-collection were conducted over fourteen days between April 2015 - October 2022 with support from multiple cooperators. NOTE: Files marked as preliminary are provisional and are subject to revision. They are being provided to meet the need for timely best science. The data have not received final approval by the U.S. Geological Survey (USGS) and are provided...
Categories: Data,
Data Release - In Progress;
Tags: Cache Slough,
California,
Central Valley,
Lower Sacramento,
Sacramento River,
Data was collected in the Cache Slough Complex located in the northern San Francisco Estuary to characterize water quality parameters at high spatial resolution. Data collection was conducted on three separate occasions: October 2017, May 2018, and October 2018. Data set includes nitrate, ammonium, ortho-phosphate, dissolved organic carbon, temperature, conductivity, dissolved oxygen, turbidity, chlorophyll, stable isotopes including water isotopes. Measurements were used to calculate evaporation to inflow ratios and water residence time.
This is the USGS California Water Science Center's Catalog and Repository space. This space primarily supports CAWSC science projects by providing a place to organize and publicly release data which cannot fit within the USGS's National Water Information System. The CAWSC mission is to collect, analyze and disseminate impartial hydrologic data and information needed to wisely manage water resources for the people of the United States and the State of California. CAWSC Web site: http://ca.water.usgs.gov/
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: California,
biogeochemistry,
ecology,
geochemistry,
groundwater,
Fluxes of CO2 during the snow-covered season contribute to annual carbon budgets, but our understanding of the mechanisms controlling the seasonal pattern and magnitude of carbon emissions in seasonally snow-covered areas is still developing. In a subalpine meadow on Niwot Ridge, Colorado, soil CO2 fluxes were quantified with the gradient method through the snowpack in winter 2006 and 2007 and with chamber measurements during summer 2007. The CO2 fluxes of 0.71 ?mol m?2 s?1 in 2006 and 0.86 ?mol m?2 s?1 in 2007 are among the highest reported for snow-covered ecosystems in the literature. These fluxes resulted in 156 and 189 g C m?2 emitted over the winter, ~30% of the annual soil CO2 efflux at this site. In general,...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Biogeochemistry,
CO2 flux,
Carbon cycle,
Climate change,
Snowpack,
Physical ecosystem engineers are organisms that physically modify the abiotic environment. They can affect biogeochemical processing by changing the availability of resources for microbes (e.g., carbon, nutrients) or by changing abiotic conditions affecting microbial process rates (e.g., soil moisture or temperature). Physical ecosystem engineers can therefore create biogeochemical heterogeneity in soils and sediments. They do so via general mechanisms influencing the flows of materials (i.e., modification of fluid dynamic properties, fluid pumping, and material transport) or the transfer of heat (i.e., modification of heat transfer properties, direct heat transfer, and convective forcing). The consequences of physical...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: BioScience,
biogeochemistry,
heterogeneity,
physical ecosystem engineering,
sediments,
Research in river-floodplain systems has emphasized the importance of nutrient delivery by floodwaters, but the mechanisms by which floods make nutrients available are rarely evaluated. Using a laboratory re-wetting experiment, we evaluated the alternative hypotheses that increased nutrient concentrations in riparian groundwater during flash floods are due to (HI) elevated nutrient concentrations in surface floodwaters entering the riparian zone or (H2) re-mobilization of nutrients from riparian soils. We sampled soils from the riparian zone of a 400 m reach of Sycamore Creek, AZ. Two sub-samples from each soil were re-wetted with a solution that mimicked the chemistry of floodwaters, with one subsample simultaneously...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Biogeochemistry,
Springer,
desert stream,
flash flood,
nutrient sources,
The purpose of my research group is to develop new methods and applications of environmental isotopes to solve problems of national importance. In specific, the overall goal is to use environmental isotopes, combined with other biogeochemical measurements and hydrologic and biogeochemical modeling, to increase our understanding of biogeochemical and hydrological processes, nutrient and organic matter sources, subsurface flowpaths, and water age distributions in diverse environments. Many of our studies piggyback on the sampling efforts of major monitoring programs to investigate causes of hypoxia and food web problems. Our work provides critical scientific support for these monitoring programs. A long-term career...
I study biogeochemical cycling in aquatic ecosystems. Current projects include 1) Trends in alkalinity and acidity in coastal rivers of the US and potential effects on coastal acidification (USGS NAWQA Trends Team). 2) Continental-scale synthesis of stream metabolism and its links to water quality and the aquatic carbon cycle (USGS Powell Center; USGS NAWQA; USGS NRP). 3) Carbon transport and cycling in the Upper Mississippi River basin (USGS LandCarbon). 4) Long-term trends in acidification of the Delaware River Estuary (Penn State University). 5) Hyporheic exchange in contrasting headwater streams of the Colorado Front Range (with Colorado School of Mines).
Categories: Project;
Tags: Biogeochemistry,
Carbon Cycling and Sequestration,
Nutrients,
Rivers and Streams,
Stream Metabolism,
Nitrates minerals from the Dry Valleys of Antarctica have been analyzed for their oxygen and nitrogen isotopic compositions. The 15N was depleted with δ15N values ranging from −9.5 to −26.2‰, whereas the 17O and 18O isotopes were highly enriched (with excess 17O) with δ18O values spanning 62–76‰ and Δ17O values from 28.9 to 32.7‰. These are the largest 17O enrichments observed in any known mineral. The oxygen isotopes indicate that nitrate is from a combination of tropospheric transport of photochemically produced HNO3 and HNO3 formed in the stratosphere.
The U.S. Geological Survey monitored algal biomass accrual and concentrations of metals and other trace elements in stream water and periphytic algae at 3-4 day intervals over a 2-week period at 3 locations within the upper and middle portions of the mining-impacted Clark Fork River, Montana, and at one location on the relatively unimpacted Blackfoot River tributary. This data release makes available trends in major and minor trace element concentrations in surface water and periphytic algae, and corresponding trends in concentrations of autotrophic (chlorophyll a) and heterotrophic (ash-free dry mass) algal biomass collected in late July and early August 2015.
Categories: Data;
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Aquatic Biology,
Black Foot River,
Botany,
Clark Fork River,
Ecology,
This data release documents the spatial and temporal variability of nutrients and related water quality parameters at high spatial resolution in the western and central portion of the Sacramento-San Joaquin River Delta of California, USA. The data set includes water residence time, nitrate, ammonium, phosphate, dissolved organic carbon, temperature, conductivity, dissolved oxygen, turbidity, and chlorophyll. Data collection were conducted over six days between August 2015 - July 2016 to document conditions prior to, during, and following the installation of a rock barrier on False Barrier to limit salt intrusion.
Categories: Data;
Tags: California,
Central Valley,
Geochemistry,
Sacramento River,
Sacramento-San Joaquin Delta,
|
|
