Filters: Tags: Biogeochemistry (X)593 results (9ms)
Data on denitrification and ecological characteristics of nontidal floodplains, Chesapeake Bay watershed, USA, 2013-2016
This data set presents attributes of floodplain ecosystem characteristics including floodplain soil denitrification, floodplain soil biogeochemistry, floodplain vegetation, floodplain sedimentation, floodplain and channel morphometry, stream discharge and water quality, floodplain climate, floodplain physiographic region, and catchment land cover. Attributes are associated with 18 floodplains of the Chesapeake Bay watershed. For many of these attributes, mean values are summaries of multiple measurements made within each floodplain site.
Environmental influences on the super(137)Cs kinetics of the yellow-bellied turtle (Trachemys scripta)
Summer nitrate uptake and denitrification in an upper Mississippi River backwater lake: The role of rooted aquatic vegetation
In-stream nitrogen processing in the Mississippi River has been suggested as one mechanism to reduce coastal eutrophication in the Gulf of Mexico. Aquatic macrophytes in river channels and flood plain lakes have the potential to temporarily remove large quantities of nitrogen through assimilation both by themselves and by the attached epiphyton. In addition, rooted macrophytes act as oxygen pumps, creating aerobic microsites around their roots where coupled nitrification-denitrification can occur. We used in situ 15N-NO3- tracer mesocosm experiments to measure nitrate assimilation rates for macrophytes, epiphyton, and microbial fauna in the sediment in Third Lake, a backwater lake of the upper Mississippi River...
Coastal zone managers need to factor submarine groundwater discharge (SGD) in their integration. SGD provides a pathway for the transfer of freshwater, and its dissolved chemical burden, from the land to the coastal ocean. SGD reduces salinities and provides nutrients to specialized coastal habitats. It also can be a pollutant source, often undetected, causing eutrophication and triggering nuisance algal blooms. Despite its importance, SGD remains somewhat of a mystery in most places because it is usually unseen and difficult to measure. SGD has been directly measured at only about a hundred sites worldwide. A typology generated by the Land-Ocean Interaction in the Coastal Zone (LOICZ) Project is one of the few...
Changes in the character of DOC in streams during storms in two Midwestern watersheds with contrasting land uses
Dissolved organic carbon (DOC) dynamics in streams is important, yet few studies focus on DOC dynamics in Midwestern streams during storms. In this study, stream DOC dynamics during storms in two Midwestern watersheds with contrasting land uses, the change in character of stream DOC during storms, and the usability of DOC as a hydrologic tracer in artificially drained landscapes of the Midwest are investigated. Major cation/DOC concentrations, and DOC specific UV absorbance (SUVA) and fluorescence index (FI) were monitored at 2-4 h intervals during three spring storms. Although DOC is less aromatic in the mixed land use watershed than in the agricultural watershed, land use has little impact on stream DOC concentration...
We studied the chemical and optical changes in the dissolved organic matter (DOM) from two freshwater lakes and a Sphagnum bog after exposure to solar radiation. Stable carbon isotopes and solid-state 13C-NMR spectra of DOM were used together with optical and chemical data to interpret results from experimental exposures of DOM to sunlight and from seasonal observations of two lakes in northeastern Pennsylvania. Solar photochemical oxidation of humic-rich bog DOM to smaller LMW compounds and to DIC was inferred from losses of UV absorbance, optical indices of molecular weight and changes in DOM chemistry. Experimentally, we observed a 1.2??? enrichment in ??13C and a 47% loss in aromatic C functionality in bog DOM...
Chemical characteristics of particulate, colloidal, and dissolved organic material in Loch Vale Watershed, Rocky Mountain National Park
The chemical relationships among particulate and colloidal organic material and dissolved fulvic acid were examined in an alpine and subalpine lake and two streams in Loch Vale Watershed, Rocky Mountain National Park. The alpine lake, Sky Pond, had the lowest dissolved organic carbon (DOC) (0.37 mgC/L), the highest particulate carbon (POC) (0.13 mgC/L), and high algal biomass. The watershed of Sky Pond is primarily talus slope, and DOC and POC may be autochthonous. Both Andrews Creek and Icy Brook gain DOC as they flow through wet sedge meadows. The subalpine lake, The Loch, receives additional organic material from the surrounding forest and had a higher DOC (0.66 mgC/L). Elemental analysis, stable carbon isotopic...
Complementarity of light and water use in tropical agroforests I. Theoretical model outline, performance and sensitivity
Temporal variability of amino acid, hexosamine, and carbohydrate fluxes on the eastern Brazilian continental margin related to discharge of the Sao Francisco River, Brazil
Geochemical and Microbiological Methods for Evaluating Anaerobic Processes in an Aquifer Contaminated by Landfill Leachate
Initial responses of phosphorus biogeochemistry to calcium addition in a northern hardwood forest ecosystem
Recent work in seasonally snow covered ecosystems has identified thawed soil and high levels of heterotrophic activity throughout the winter under consistent snow cover. We performed measurements during the winter of 1994 to determine how the depth and timing of seasonal snow cover affect soil microbial populations, surface water NO3/- loss during snowmelt, and plant N availability early in the growing season. Soil under early accumulating, consistent snow cover remained thawed during most of the winter and both microbial biomass and soil inorganic N pools gradually increased under the snowpack. At the initiation of snowmelt, microbial biomass N pools increased from 3.0 to 5.9 g N m-2, concurrent with a decrease...