Filters: Tags: Biogeochemistry (X)
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Surface water quality, water isotope, and phytoplankton enumeration data were collected to evaluate the impact of an Emergency Drought Barrier (EDB) in False River in the Sacramento-San Joaquin Delta. Data were collected on six days during 2022 and 2023 (June 7, June 21, July 27, August 9, October 12, November 30, 2022, and February 21, 2023). Sampling occurred in Franks Tract, Mildred Island, the San Joaquin River, and various sloughs and cuts connecting these water bodies. High-resolution boat-based mapping data and discrete water samples were collected and analyzed for: nitrate, nitrite, ammonium, soluble reactive phosphorus (orthophosphate), total dissolved nitrogen, total dissolved phosphorus, total phosphorus,...
The Gulf of Alaska is one of the most productive marine ecosystems on Earth, supporting salmon fisheries that alone provide large economic benefits to Southeast Alaska. The region also has a vibrant and growing tourism industry. Glaciers are central to many of the area’s natural processes and economic activities, but the rates of glacier loss in Alaska are among the highest on Earth. Glacier loss threatens to significantly change the amount and timing of nutrients delivered by streams to near-shore habitats. Changes in glacier runoff into the ocean may also impact coastal currents that contribute to vibrant nearshore marine ecosystems. Improving our understanding of how ecosystems depend on glaciers and what glacier...
Categories: Project;
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: 2015,
Alaska,
Alaska CASC,
CASC,
Forests,
Hurricanes cause severe impacts on forest ecosystems in the United States. These events can substantially alter the carbon biogeochemical cycle at local to regional scales. We selected all tropical storms and more severe events that made U.S. landfall between 1900 and 2011 and used hurricane best track database, a meteorological model (HURRECON), National Land Cover Database (NLCD), U. S. Department of Agirculture Forest Service biomass dataset, and pre- and post-MODIS data to quantify individual event and annual biomass mortality. Our estimates show an average of 18.2 TgC/yr of live biomass mortality for 1900–2011 in the US with strong spatial and inter-annual variability. Results show Hurricane Camille in 1969...
Categories: Publication;
Types: Journal Citation;
Tags: Biogeochemistry,
Carbon cylce,
Carbon flux,
Ecological modelling,
Hurricanes
Metals and metalloids occur in the environment both as natural constituents of water and as contaminants. The focus of my research is to identify and develop geochemical and particularly isotopic approaches to identifying the sources, transport mechanisms and fates of those metals and metalloids, and to use these novel tracer tools to study hydrologic and biogeochemical processes in varied field and laboratory situations. Examples of current research objectives are: 1) to use isotopes of the alkaline earth elements (Ca, Sr, Ba) to determine water flowpaths and solute sources in headwater catchments; 2) to use isotopes of Cr to understand Cr transport and contaminant remediation at industrial sites and in rivers;...
Denitrification, the anaerobic reduction of nitrogen oxides to nitrogenous gases, is an extremely challenging process to measure and model. Much of this challenge arises from the fact that small areas (hotspots) and brief periods (hot moments) frequently account for a high percentage of the denitrification activity that occurs in both terrestrial and aquatic ecosystems. In this paper, we describe the prospects for incorporating hotspot and hot moment phenomena into denitrification models in terrestrial soils, the interface between terrestrial and aquatic ecosystems, and in aquatic ecosystems. Our analysis suggests that while our data needs are strongest for hot moments, the greatest modeling challenges are for hotspots....
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Biogeochemistry,
Denitrification,
Nitrogen,
Riparian,
Sediment,
Most of my current efforts are committed to multi-catchment investigations designed to distinguish the roles of vegetation, climate, and land-cover change and to put these in a hydrologic and biogeochemical framework as well as to examine ecosystem costs and services focusing on water, carbon, and biodiversity. Two projects consume most of my efforts: (1) Work related to the Luquillo USGS Water, Energy, and Biogeochemical Budget (WEBB) Project in eastern Puerto Rico and parallel work in Panama is in the modeling and write-up phase (60% time). The objective is a comprehensive assessment of catchment hydrology and biogeochemistry in a humid-tropical landscape. In Puerto Rico we compare two rock types, quartzose and...
Categories: Project;
Tags: Biogeochemistry,
Carbon Cycling and Sequestration,
Nutrients,
Rivers and Streams,
Watershed Studies
Recent research has dramatically advanced our understanding of soil organic matter chemistry and the role of N in some organic matter transformations, but the effects of N deposition on soil C dynamics remain difficult to anticipate. We examined soil organic matter chemistry and enzyme kinetics in three size fractions (>250 μm, 63–250 μm, and <63 μm) following 6 years of simulated atmospheric N deposition in two ecosystems with contrasting litter biochemistry (sugar maple, Acer saccharum—basswood, Tilia americana and black oak, Quercus velutina—white oak, Q. alba). Ambient and simulated (80-kg NO3 −–N ha−1 year−1) atmospheric N deposition were studied in three replicate stands...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Biogeochemistry,
Carbon structure,
Enzymes,
Nitrogen deposition,
Pyrolysis gas chromatography/mass spectrometry,
My research goals are (1) to develop reaction-transport models with varying levels of complexity and data requirements, providing guidelines for the appropriate application of these models given field conditions and limited resources; (2) to incorporate the effects of surface-chemistry phenomena into reaction-transport modeling; (3) to develop methods to identify and quantify important chemical and biological reactions affecting transport of inorganic and organic substances; and (4) to compile estimates of reaction rates and reaction-rate laws for chemical and biological reactions. In addition to model development, the project undertakes field, laboratory, and theoretical studies to investigate field-scale chemical...
This data release documents the spatial and temporal variability of nutrients and related water quality parameters at high spatial resolution in the North Delta 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 cruises were conducted under three different environmental/flow conditions in August, September, and October 2018 that coincided with conditions prior to, during, and following a directed flow action or pulse of agricultural return water organized by the California Department of Water Resources and California Natural Resources Agency...
Categories: Data;
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: California,
Central Valley,
Directed Flow Action,
Liberty Island,
Sacramento River,
Clear Lake is a 180 km2 freshwater lake located in the California Coast Range, approximately 120 km northwest of Sacramento. The lake supports a wide variety of fish and bird species and is a very popular sport-fishing destination. However, fish consumption advisories associated with mercury (Hg) contamination exist for several popular recreational species. The lake is comprised of three main regions including a large open-water region to the northwest (North Arm), a smaller and narrower region to the southeast (South Arm), and the smallest and narrowest region to the east (Oaks Arm). The Sulfur Bank Mercury Mine (SBMM), located on the south shore of the Oaks Arm, was mined by both open-pit and underground methods...
Mercury (Hg) is a well-known toxic element and environmental contaminant. The central valley of California has long been identified as a hotspot for Hg contamination due to the historic mining of Hg in the California coast range, and its use in the mining of gold in the Sierra Nevada, with these mountainous regions bordering the east and the west of the valley, respectively. While the whole central valley is world renowned as a major agricultural area, the northern portion, known as the Sacramento valley region, is dominated by commercial rice production. Since rice is grown in flooded fields, and since wetland soils are known to be particularly effective habitats for converting inorganic mercury into the more toxic...
Categories: Data;
Tags: California,
Environmental Health,
Geochemistry,
Sacramento Valley,
Sacramento-San Joaquin Delta,
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