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Full-Text Articles in Earth Sciences
Examining Denitrification In Agricultural Ditch Sediments Vegetated With Rice Cutgrass (Leersia Oryzoides): Modeling Seasonal Variation Across Increasing Levels Of Nitrate Loading And Model Application To Pre-Existing Datasets, Shannon Lee Speir
Graduate Theses and Dissertations
Nitrogen (N) derived from fertilizer application in agricultural systems may contribute to significant environmental impacts, including eutrophication of fresh and coastal waters. Rice cutgrass (Leersia oryzoides) can significantly enhance denitrification potential in agricultural ditch sediments, but relationships with known drivers are not well understood. To address this, I examined effects of nitrate (NO3-) availability on dinitrogen gas (N2) and NO3- fluxes seasonally in Chapter 2. Denitrification rates were measured as N2 flux from intact vegetated sediment cores using Membrane Inlet Mass Spectrometry (MIMS). Michaelis-Menten models were developed from observations to mathematically describe N2 fluxes across the spring, summer, and fall …
Investigation Of The Flow And Fate Of Nitrate In Epikarst At The Savoy Experimental Watershed, Northwest Arkansas, Jozef Laincz
Investigation Of The Flow And Fate Of Nitrate In Epikarst At The Savoy Experimental Watershed, Northwest Arkansas, Jozef Laincz
Graduate Theses and Dissertations
Many karst aquifers are at high risk of nitrate contamination due to a combination of vulnerable geology characterized by thin soils and conduit flow, and excess inputs of nutrients from animal feeding operations. One zone that is present in many karst regions and could play an important role in nitrate attenuation due to properties such as increased residence time and matrix-water contact is the upper, weathered portion of karst, the epikarst. However, the understanding of this role is lacking, and the objective of this dissertation was to elucidate it. The fate of nitrate in the epikarst was traced along a …
Nitrogen Retention And Denitrification In Reservoirs, Erin Grantz
Nitrogen Retention And Denitrification In Reservoirs, Erin Grantz
Graduate Theses and Dissertations
Studies coupling direct measurements of micro-scale nitrogen (N) cycle processes with ecosystem-scale flux estimates are needed to determine N retention hotspots within river networks, where up to 50% of terrestrial loading to aquatic systems is retained. This study examined the role of denitrification, a microbially-mediated reactive N removal pathway, in ecosystem-scale N retention in 3 small (< 1 km2), shallow flood-control reservoirs. Annual reservoir N retention was estimated through mass balance modeling of system inputs and outputs. Annual denitrification rates were estimated by combining multiple measurements of seasonal, habitat-specific dinitrogen gas (N2) fluxes. Annual reservoir N retention ranged from 14 - 19 g m-2 in the reservoirs, while reactive N removal through denitrification was 13 - 25 g m-2. Denitrification efficiency, or the portion of the retained N load that was denitrified, was high relative to other lentic systems and was > 100% at 2 sites. Previous lentic denitrification studies may have underestimated denitrification efficiency by not considering water column denitrification, which was 50% of total denitrification at one study reservoir. However, not all potential inputs, most importantly biological N2 fixation, were included in this …