Download or read book Investigation of Nitrogen Cycling Using Stable Nitrogen and Oxygen Isotopes in Narragansett Bay RI written by Courtney Elizabeth Schmidt and published by . This book was released on 2014 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stable Isotope Methods for the Study of the Nitrogen Cycle written by Evgenia Ryabenko and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Stable Isotope Methods for the Study of the Nitrogen Cycle.

Download or read book Stable Nitrogen Isotopes as a Tool for Understanding Nitrogen Cycling Processes and Mechanisms Responsible for Nitrous Oxide Production written by Robin Leslie Sutka and published by . This book was released on 2002 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Using Stable Nitrogen Isotopes to Characterize and Evaluate Nitrogen Sources to Greenwich Bay RI and Their Influence on Isotopic Signatures in Estuarine Organisms written by Peter A. Dimilla and published by . This book was released on 2006 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stable Isotopes of Nitrite as a Tool for Understanding Nitrogen Cycling and Loss in Oxygen Deficient Zones written by Taylor Martin and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrogen (N), a key nutrient in the global ocean, has a complicated biogeochemical cycle. In the ocean, nitrogen is mainly found as nitrate (NO3-), but it also accumulates as nitrite (NO2-) within oxygen deficient zones (ODZs). Nitrite is a key intermediate in several processes that produce nitrous oxide (N2O), a potent greenhouse gas. Using natural abundance stable isotope measurements of NO3- and NO2- help to capture an integrated signal of the N cycle processes. My doctoral work aims to use stable isotopes of N and oxygen (O) in order to further our understanding of the pathways that produce and consume NO2-, which will help us better predict the global impacts of nitrogen cycling both at present and in the future. Many N cycle processes are microbially mediated and impart one or more unique isotope effects on its N substrates and products, and it is important to quantify these isotope effects in order to use numerical models to elucidate relative contributions of different N cycle processes. In Chapter 1, I use pure culture experiments to better constrain estimates of the N and O isotope effects of microbial nitrite reduction, a key step in the process of denitrification, which leads to loss of bioavailable N. I then use the values from this experiment, in conjunction with previous estimates of other N cycle process isotope effects, to model observed NO3- and NO2- data from the Arabian Sea (Chapter 2) and explore the necessity for oxygen-requiring processes within the ODZ. In Chapter 3, I expand upon the results from previous chapters by applying the results to a global 3D inverse model of the N cycle, which includes isotopic fractionation, in order to examine the NO2- production and consumption processes within marine ODZs. I also examine the sensitivity of NO3- and NO2- concentration and isotope profiles to controlling parameters of N cycle processes, such as oxygen thresholds and isotope effects, in order to examine the roles of individual processes in N loss, and their potential for future change.

Download or read book Nitrogen Cycling in the Past and in the Present Mediterranean Sea and Arabian Sea written by Jürgen Henning Möbius and published by . This book was released on 2010 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nitrogen Cycling in the Southern North Sea written by Kirstin Dähnke and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nitrogen Cycling in Shallow Low Oxygen Coastal Waters Off Peru from Nitrate and Nitrate Nitrogen and Oxygen Isotopes written by Haibei Hu and published by . This book was released on 2015 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Science of Ecosystem based Management written by Alan Desbonnet and published by Springer Science & Business Media. This book was released on 2008-01-12 with total page 577 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the U.S., approximately two-thirds of the coastal rivers and bays are moderately to severely degraded from nutrient pollution. The contributors to this book use long-term data sets to discuss the interactions among biological, ecological, chemical, and physical processes, and discuss what is known about nutrient inputs to the bay ecosystem, the impacts related to nutrient inputs, and how the ecosystem might respond to a sudden reduction in these inputs.

Download or read book Nitrogen Cycling in Oxygen Deficient Zones written by Carolyn Buchwald and published by . This book was released on 2013 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: The stable isotopes, [delta]15N and [delta]18O, of nitrite and nitrate can be powerful tools used to interpret nitrogen cycling in the ocean. They are particularly useful in regions of the ocean where there are multiple sources and sinks of nitrogenous nutrients, which concentration profiles alone cannot distinguish. Examples of such regions are "oxygen deficient zones" (ODZ). They are of particular interest because they are also important hot spots of fixed N loss and production of N2O, a potent greenhouse gas. In order to interpret these isotope profiles, the isotope systematics of each process involved must be known so that we can distinguish the isotopic signature of each process. One of the important processes to consider here is nitrification, the process by which ammonium is oxidized nitrite and then to nitrate. This thesis describes numerous experiments using both cultures of nitrifying organisms as well as natural seawater samples to determine the oxygen isotope systematics of nitrification. These experimental incubations show that the accumulation of nitrite has a large effect on the resulting [delta]18ONO3. In experiments where nitrite does not accumulate, [delta]18ONO3 produced from nitrification is between -1 to l%o. These values will be applicable for the majority of the ocean, but the nitrite isotopic exchange will be important in the regions of the ocean where nitrite accumulates, such as the base of the euphotic zone and oxygen deficient zones. [delta]18ONO2 was developed as a unique tracer in this thesis because it undergoes abiotic equilibration with water [delta]18O at a predictable rate based on pH, temperature and salinity. This rate, its dependencies, and how the [delta]18ONO2 values can be used as not only biological source indicators but also indicators of age are described. This method was applied to samples from the primary nitrite maximum in the Arabian Sea, revealing that the dominant source and sinks of nitrite are ammonia oxidation and nitrite oxidation with an average age of 37 days. Finally, using the isotope systematics of nitrification as well as the properties of nitrite oxygen isotope exchange described in this thesis, the final chapter interprets multiisotope nitrate and nitrite profiles in the Costa Rica Upwelling Dome using a simple ID model. The nitrite isotopes showed that there were multiple sources of nitrite in the primary nitrite maximum including (1) decoupling of ammonia oxidation and nitrite oxidation, (2) nitrate reduction during assimilation and leakage of nitrite by phytoplankton. In the oxygen deficient zone and secondary nitrite maximum, there were equal contributions of nitrite removal from nitrite oxidation and nitrite reduction. This recycling of nitrite to nitrate through oxidation indicates that the percentage of reduced nitrate fully consumed to N2 gas is actually smaller than previous estimates. Overall, this thesis describes new nitrogen and oxygen isotopic tracers and uses them to elucidate the complicated nitrogen biogeochemistry in oxygen deficient zones.

Download or read book The Use of Stable Nitrogen and Carbon Isotopes to Examine the Sources Sinks and Cycling of Nitrogen in a Small Artificially Eutrophic Boreal Lake written by Nicholas Alexander Paquette Flinn and published by . This book was released on 2012 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research examines components of nitrogen cycling in the artificially eutrophic Lake 227 at the Experimental Lakes Area. The components are: 1) the atmospheric sources of nitrogen to the lake through precipitation and dry deposition; 2) the sediment record of past nitrogen sources and primary productivity; and 3) the internal processes of nitrogen cycling. These topics are examined using stable nitrogen and carbon isotopes. The [delta]15N of atmospheric nitrogen deposition in Canada is not well studied. The results of this work are the first [delta]15N-NH4+ values for Canada, while the [delta]15N-NO3- values add to a very limited data base for Canada.

Download or read book Development and Application of a New Method to Reconstruct Terrestrial Nitrogen Cycling from Isotopes of Plant Compounds in Soil written by Sara Katrin Enders and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrogen availaiblity influences terrestrial productivity and global carbon cycling, with strong feedbacks to Earth's climate system. Natural abundance stable isotope ratios of nitrogen ([delta]15N) of plant leaves [delta]15N[subscript f] have provided information on large-scale patterns of N availbility in the modern environment. Few tools have been available, however, for quantitatively reconstructing past plant [delta]15N[subscript f]. We here explore the potential for chlorins, degradation products of the chlorophyll molecule with a history of use as paleo-proxies in subaqueous sediments, to be extracted from soils for use as a proxy for [delta]15N[subscript f]. In Chapter 1, we confirm that chlorins are present at depth in mineral soils. Pheophytin a (pheo a) is present in concentrations sufficient for isotopic analysis. We here test the hypothesis that [delta]15N[subscript f] is recorded in pheo a [delta]15N along the leaf-litter-soil continuum across an array of ecosystem conditions and plant functional types (C3, C4, legumes, woody plants). We report plant pheo a [delta]15N ([delta]15N [subscript phe]) and [delta]15N[subscript f] of six species across a climate gradient on Kohala Mountain of Hawaii, and find that [delta]15N[subscript phe] tracks [delta]15N[subscript f] over a wide range of environmental conditions. In Chapter 2, we examine the persistence and behavior of pheo a in soil depth profiles, through an isotope label tracer study that investigates recovery of pheo a enriched in 15N and 13C applied as isotopically-labelled leaf litter 15 years ago. We find that pheo a decays at rates comparable to bulk soil organic matter, and that pheo a has minimal downward mobility in the soil over time. In Chapter 3, we apply the [delta]15N[subscript phe] proxy in a 40 ky Siberian permafrost record to investigate changes in N cycling on that landscape through a cycle of glaciation and accompanying changes in climate, species, and atmospheric pCO2. We examine major drivers of N cycle dynamics, and compare the sensitivity of internal N cycling (recorded in [delta]15N[subscript phe]) with input-output fluxes (recorded in [delta]15N of bulk soil). The overarching picture revealed is one of bounded variability of the N cycle, with much greater sensitivity [delta]15N[subscript phe] relative to [delta]15N of bulk soil, which shows little variation over time. The rise in pCO2 accompanying deglaciation over the last ~20ky is not associated with isotopic evidence for progressive limitation by N; rather, the changing environmental conditions appear to stimulate new sources of N on this landscape, such as diazatrophic fixation or organic mineralization, and [delta]15N values indicate that N cycling stays within previous limits. These results depart from those of Free Air Carbon Dioxide (pCO2) Enrichment (FACE) experiments, which have seen a decline in [delta]15N[subscript f] and indications that that N may become more limiting to plant growth under elevated pCO2. This result suggests the overriding importance of other changing environmental variables for N cycling at high latitudes over past periods of pCO2 increase, or a compensating mechanism in the terrestrial N cycle beyond the window of experiments and within the window of global climate models.

Download or read book Identification and Quantification of Diffuse Nitrogen Inputs by Means of Stable Nitrogen and Oxygen Isotopes in Nitrate written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Examination of the Marine Nitrogen Cycle written by Fabian C. Batista and published by . This book was released on 2016 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paleoceanographic studies typically employ stable nitrogen isotopic measurements of total combustible N (delta15NTN) from marine sediments to infer temporal changes in surface ocean marine N dynamics. However, delta 15NTN is a highly non-specific measurement, susceptible to confounding issues including non-marine N sources, and offers little, if any, information regarding degradation and/or alteration of primary delta 15N signals. Recent development of novel biomarker and microfossil based proxies provide new analytical capabilities to circumvent issues with delta 15NTN.

Download or read book Nitrogen Cycling in the North Atlantic Ocean and Its Watersheds written by and published by . This book was released on 1996 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Selected Water Resources Abstracts written by and published by . This book was released on 1989 with total page 1296 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Oceanic Abstracts written by and published by . This book was released on 1996 with total page 826 pages. Available in PDF, EPUB and Kindle. Book excerpt: