Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 206-221).

Thesis (M.S.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 36-40)

Understanding the mechanisms of non-point source carbon and nutrients in urban watersheds will help to develop policies to maintain surface water quality and prevention of eutrophication. The purpose of this dissertation is to investigate the impact of sodium on carbon and nutrient leaching from the two main contributors; soil and leaf litter, and calculate the sodium exports in a humid subtropical urban river basin. The first chapter reviews the current literature on urbanization in watersheds. Chapter II quantifies the carbon and nutrient in intact soil core leachates and in water extractable solution from urban soils collected from 33 towns and cities across the state of Texas. Chapter III investigates the impact of sodicity and salinity on water extractable organic carbon and nitrogen from vegetation. Chapter IV investigates the export of sodium and chloride from the upper Trinity River basin. The results derived from this study indicate that sodium exports are elevated in urban watersheds and further that sodium in irrigation water elevates the loss of carbon and nutrients from both watershed soil and senesced vegetation and that this may contribute to high concentrations in urban freshwaters.

The biogenic reduction of Mn(IV) oxides is one of the most favorable anaerobic electron transfer processes in aquatic systems and likely plays an important role in the redox cycle of both carbon and nitrogen in anaerobic environments; yet, the different pathways involved in the microbial transformation of Mn(IV) oxides remain unclear. The coupling between the reduction of Mn(IV) to Mn(II) and the oxidation of organic carbon to CO₂ is largely catalyzed by microorganisms in various environments such as redox stratified water columns and sediments. The recent discovery that soluble Mn(III) exists in natural systems and is formed during biological oxidation of Mn(II) implies the possibility that Mn(III) is formed as an intermediate during the microbial reduction of Mn(IV). In this dissertation, mutagenesis studies and kinetic analysis were combined to study the mechanism of microbial reduction of Mn(IV) by Shewanella oneidensis MR-1, one of the most studied metal-respiring prokaryotes. We show for the first time that the microbial reduction of Mn(IV) proceeds step-wise via two successive one-electron transfer reactions with soluble Mn(III) as intermediate produced in solution. The point mutant strain Mn3, generated via random chemical mutagenesis, presents a unique phenotype that reduces solid Mn(IV) to Mn(III) but not to Mn(II), suggesting that these two reduction steps proceed via different electron transport pathways. Mutagenesis studies on various in-frame deletion mutant strains demonstrate that the reduction of both solid Mn(IV) and soluble Mn(III) occurs at the outer membrane of the cell and Mn(IV) respiration involves only one of the two potential terminal reductases (c-type cytochrome MtrC and OmcA) involved in Fe(III) respiration. Interestingly, only the second electron transfer step is coupled to the respiration of organic carbon, which opposes the long-standing paradigm that microbial reduction of Mn(IV) proceeds via the single transfer of two electrons coupled to the mineralization of carbon substrates. The coupling between anaerobic nitrification and Mn reduction has been demonstrated to be thermodynamically favorable. However, the existence of this process in natural system is still in debate. In this dissertation, characterization of coastal marine sediments was combined with laboratory incubations of the same sediments to investigate the effect of Mn oxides on the redox cycle of nitrogen. Our slurry incubations demonstrate that anaerobic nitrification is catalyzed by Mn oxides. In addition, mass balance calculations on NH₄⁺ link the consumption of NH₄⁺ to anaerobic ammonium oxidation in the presence of Mn oxides and confirm the occurrence of Mn(IV)-catalyzed anaerobic nitrification. The activity of anaerobic nitrification is greatly affected by the initial ratio of Mn(IV) to NH₄⁺, the reactivity of Mn oxides, and the reducing potential of the system. Overall, Mn(IV)-catalyzed anaerobic nitrification may be an important source of nitrite/nitrate in anaerobic marine sediments and provide an alternative pathway for subsequent nitrogen losses in the marine nitrogen cycle.

Microbial metal reduction contributes to biogeochemical cycling, and reductive precipitation provides the basis for bioremediation strategies designed to immobilize radionuclide contaminants present in the subsurface. Facultatively anaerobic ×-proteobacteria of the genus Shewanella are present in many aquatic and terrestrial environments and are capable of respiration on a wide range of compounds as terminal electron acceptor including transition metals, uranium and transuranics. S. putrefaciens is readily cultivated in the laboratory and a genetic system was recently developed to study U(VI) reduction in this organism. U(VI) reduction-deficient S. putrefaciens point mutant Urr14 (hereafter referred to as CCMB1) was found to retain the ability to respire several alternate electron acceptors. In the present study, CCMB1 was tested on a suite of electron acceptors and found to retain growth on electron acceptors with high reduction potential (E¡¬0) [O2, Fe(III)-citrate, Mn(IV), Mn(III)-pyrophosphate, NO3-] but was impaired for anaerobic growth on electron acceptors with low E¡¬0 [NO2-, U(VI), dimethyl sulfoxide, trimethylamine N-oxide, fumarate, ×-FeOOH, SO32-, S2O32-]. Genetic complementation and sequencing analysis revealed that CCMB1 contained a point mutation (H108Y) in a CcmB homolog, an ABC transporter permease subunit required for c-type cytochrome maturation in E. coli. The periplasmic space of CCMB1 contained low levels of cytochrome c and elevated levels of free thiol equivalents (-SH), an indication that redox homeostasis was disrupted. Anaerobic growth ability, but not cytochrome c maturation activity, was restored to CCMB1 by adding exogenous disulfide bond-containing compounds (e.g., cystine) to the growth medium. To test the possibility that CcmB transports heme from the cytoplasm to the periplasm in S. putrefaciens, H108 was replaced with alanine, leucine, methionine and lysine residues via site-directed mutagenesis. Anaerobic growth, cytochrome c biosynthesis or redox homeostasis was disrupted in each of the site-directed mutants except H108M. The results of this study demonstrate, for the first time, that S. putrefaciens requires CcmB to produce c-type cytochromes under U(VI)-reducing conditions and maintain redox homeostasis during growth on electron acceptors with low E¡¬0. The present study is the first to examine CcmB activity during growth on electron acceptors with widely-ranging E¡¬0, and the results suggest that cytochrome c or free heme maintains periplasmic redox poise during growth on electron acceptors with E¡¬0 < 0.36V such as in the subsurface engineered for rapid U(VI) reduction or anoxic environments dominated by sulfate-reducing bacteria. A mechanism for CcmB heme translocation across the S. putrefaciens cytoplasmic membrane via heme coordination by H108 is proposed.

This high-resolution biogeochemical study investigated spatial and temporal variability in the mixing interface zones within a wetland-aquifer system near a municipal landfill in the city of Norman, Oklahoma. Steep biogeochemical gradients indicating zones of enhanced microbial activity (e.g. iron/sulfate reduction and fermentation) were found at centimeter-scale hydrological and lithological interfaces. The small resolution study was achieved by combining passive diffusion samplers with capillary electrophoresis for chemical analysis. The spatial and temporal variability of biogeochemical processes found at the interfaces was evaluated in a depth profile over a period of three years. Correlations between geochemical parameters were determined using Principal Component Analysis (PCA) and the principal factors obtained were interpreted as a dominant biogeochemical process. Factors scores were mapped by date and depth to determine the spatial-temporal associations of the dominant processes. Fermentation was the process controlling the greatest variability in the dataset followed by iron/sulfate reduction, and methanogenesis. The effect of seasonal and hydrologic changes on biogeochemistry was evaluated from samples collected in a wet/dry period from three locations exhibiting upward, downward, and negligent hydrologic flow between aquifer and wetland. PCA was used to identify the principal biogeochemical processes and to obtain factor scores for evaluating significant seasonal and hydrological differences via analysis of variance. Iron and sulfate reduction were dominated by changes in water table levels and water flow paths, whereas methanogenesis and bacterial barite utilization were dominated by season and associated with a site with negligible flow. A preliminary study on microbial response to changes in geochemical nutrients (e.g. electron acceptors and electron donors) was conducted using in situ microcosms with the purpose of quantifying iron and sulfate reduction rates. Problems encountered in the experiment such as leaks in the microcosms did not allow the determination of respiration rates, therefore the experiments will be repeated in the future. The results suggest that iron and sulfate reduction were stimulated with the addition of sulfate and ferrihydrite (electron acceptors) and acetate and lactate (electron donors). This research demonstrates the importance of assessing biogeochemical processes at interface zones at appropriate scales and reveals the seasonal and hydrological controls on system processes.

No description available.

Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Title from PDF title page (October 20, 2008) Includes bibliographical references (p. 101-106)

Subsequent to the Last Glacial Maximum (LGM), complex coastal response resulted from deglaciation, eustatic sea-level change, and a relatively thin, flexible lithosphere in the Queen Charlotte Islands (QCI) region of northwestern Canada. Presented here is an interdisciplinary study that combines the methodologies and schools of thought from geology, biology, and geography to address a research problem that spans these disciplines, specifically to illustrate the environment, temporal and spatial dimensions of isostatic crustal adjustment and the Late Quaternary coastline of the northeast Pacific continental shelf. Molluscan distribution, lithology, and published sub-bottom profiles are used to deduce sea-levels, outline the influence of glacially-induced crustal displacement, and reconstruct the paleoenvironment of the northeast Pacific Late Quaternary coastline, including the absence of ice and the presence of emergent coastal plains. These data are used to ascertain the region's suitability as a home for an early migrating coastal people. A series of paleogeographic maps and isostatic crustal displacement maps chart the sequence of evolving landscapes and display temporal changes in the magnitudes and extent of crustal flexure as a forebulge developed. The wave-length and amplitude of the glacially-induced forebulge supports thermal and refraction modeling of a thin (~25 km thick) lithosphere beneath Queen Charlotte (QC) Sound and Hecate Strait. Glacial ice at least 200 m thicker than present water depth began retreating from Dixon Entrance after 14,000 and prior to 12,640 14C years BP, generating 50 m of uplift in northern Hecate Strait. The position of the forebulge remained essentially constant after 12,750 14C years BP, implying a fixed ice-front and continued ice presence on the British Columbia (BC) mainland until ~10,000 14C years BP. A 3-dimensional model shows two ice-free terrains emerged: one extended eastward from the QCI, the other developed in QC Sound. By ~11,750 14C years BP a landbridge connected the BC mainland and QCI. Malacological evidence indicates a paucity of Arctic molluscan faima subsequent to glaciation, perhaps a consequence of shallow, narrowed straits, and the presence of ice sheets that interfered with ocean currents. Water temperature, sedimentation rates, turbidity, and photoperiod are factors that limited invertebrate colonization during the Late Pleistocene - Early Holocene. The oldest dated mollusc to colonize QCI region subsequent to LGM was Macoma nasuta at 13,210 14C years BP. Once habitat and sea-surface temperatures were conducive, rates of recolonization appear to be limited only by the availability of ocean currents to bring temperate pelagic larvae into the region from outlying areas. Between ~11,000 and 10,000 14C years BP the appearance of Clinocardium ciliatum and Serripes groenlandicus, concurrent with the disappearance, or significant reduction in number and productivity of temperate intertidal molluscs, indicates the onset of a short interval of cool sea-surface temperatures coincident with the Younger Dryas cooling event. Five molluscan species: Macoma incongrua, Musculus taylori (cf), Mytilimeria nuttallii, Tellina nucidoides, Mytilus edulis/Mytilus trossulus previously categorized as possessing a Recent geologic range were collected in sediments dating older than 10,000 14C years BP. Fossil mollusc shells indicate edible intertidal biomass densities well within commercially harvested levels on southern Moresby Island by 8,800 14C years BP, and on northern Graham Island by 8,990 14C years BP. The presence and productivity of nutritious intertidal molluscs indicates the QCI region had a suitable climate, possessed open ocean conditions, and provided subsistence resources for potential early humans subsequent to at least 13,210 14C years BP. Three-dimensional modeling shows subaerially exposed land that could have been inhabited by plants, animals, including coastal-migrating early humans. Early coastlines that have not been drowned, and which may harbour early archaeological sites, are identified along the western and northern coasts of QCI and the BC mainland. / Graduate

Este trabalho teve como proposta principal avaliar os efeitos de ações antrópicas sobre sistemas estuarinos com base no balanço biogeoquímico entre as formas de nutrientes (N, P e Si). Foram estudados dois sistemas estuarinos localizados em pontos extremos da costa, um no nordeste, o estuário do Rio Jaguaribe, no Ceará, e outro no sudeste, o complexo estuarino-lagunar de Cananéia e Iguape, em São Paulo. Estes sistemas estão sob os diferentes regimes climáticos e o estudo envolveu: aspectos dos períodos de seca e chuva nos dois locais; o efeito da maré; e, o aporte de águas doces quer sob a forma de chuva, quer via drenagem continental e barragens. A influência antrópica mostrou a ação sobre o excesso de silício nos dois sistemas. O fósforo foi o elemento dissolvido que recebeu maior ação neutralizadora, sendo \"tamponado\" de forma que não ofereceu sinais de eutrofização. Este não é o caso das formas nitrogenadas, que mostraram uma assinatura relativa às atividades antrópicas que mais impactam cada região. No caso do Rio Jaguaribe, o aporte de matéria orgânica e de nutrientes via atividade de carcinicultura colaborou ao destaque na forma de N-amoniacal nas águas do médio e baixo estuário, onde se localizam as fazendas de carcinicultura. Os sinais mais acima no sistema estiveram ligados aos aportes via barragem e da cidade de Aracati. No caso do complexo estuarino-lagunar de Cananéia e Iguape, o nitrato recebeu destaque junto aos aportes do Rio Ribeira de Iguape, por meio do Valo Grande, representando a drenagem de zonas agrícolas. A parte sul do sistema, Cananéia, mostrou um equilíbrio entre as formas nitrogenadas, bastante naturais, dando suporte à produção primária de populações comuns a ambientes estuarinos, enquanto que, os valores de pigmentos fotossintetizantes, mostraram que a composição das comunidades fitoplanctônicas se adapta às condições abióticas do corpo hídrico. Há produção em todos os locais, porém com distinção entre as comunidades fitoplanctônicas. Ocorreu influência sazonal e a degradação de biomassa vegetal, muitas vezes somadas as influências de feopigmentos de comunidades das margens. O diagnóstico feito com o Programa ASSETS é baseado em carga de nitrogênio, valores de clorofila e presença de macroalgas, contudo o equilíbrio entre os nutrientes pode ser uma excelente ferramenta na avaliação ambiental. / The main proposal of this work was to evaluate the effects of anthropic actions upon estuarine systems, based on biogeochemical balance between forms of nutrients (N, P and Si). Two estuarine systems were studied, localized in extreme points of the coast, one in northeast, Jaguaribe River estuary, in Ceará, and the other in southeast, Cananéia-Iguape estuarine-lagoon complex, in São Paulo. These systems are under different climatic patterns and the study involved: aspects of dry and rainy periods in both locations; tide effects; and fresh water inputs, either in the form of rain, or via continental drainage and dams. The anthropic influence showed action upon the excess of silicon in both systems. Phosphorus was the dissolved element that suffered bigger neutralizing action, being buffered, and so, didn\'t show signals of eutrophication. That is not the case of nitrogen\'s forms, they showed a signature related to anthropic activities that impact each region the most. In the case of Jaguaribe River, the input of organic matter and nutrients, due to shrimp farms activities, contributed to prominent N-ammonium form in medium and lower estuary waters, where shrimp farms are located; the signals in upper estuary were connected to inputs via dam and Aracati city. In the case of Cananéia-Iguape estuarine-lagoon complex, the form nitrate was highlighted by the inputs of Ribeira de Iguape River, through Valo Grande, representing agricultural areas drainage. The south part of the system, Cananéia, showed a quite natural balance between the nitrogen forms, supporting primary production of populations common to the estuarine environment. Meanwhile, values of photosynthetic pigments showed that the composition of planktonic communities adapt itself to the abiotic conditions of the water body. There is production everywhere, but with distinctions between the communities. Seasonal influence occurred, and also degradation of microscopic vegetal biomass, often added to influence of pheopigments of margin communities. The diagnosis made by ASSETS Program is based on nitrogen input, values of chlorophyll and macroalgae presence; nevertheless the equilibrium between nutrients can be an excellent tool for environmental evaluation