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Trace Metal Applications In Atmospheric And Watershed Dynamics: Case Studies Of Mercury Deposition In New England And Bedrock Groundwater-Surface Water Mixing, Melissa A. Lombard

Doctoral Dissertations

The studies presented in this dissertation focus on the environmental chemistry of two trace metals, mercury (Hg) and strontium (Sr). Both are naturally occurring and exist in the environment at trace levels.

Chapters II-IV of this dissertation focus on understanding the atmospheric chemistry of Hg and the wet and dry deposition of this toxic element. Chapter II presents results from Hg wet deposition measurements and ambient reactive gaseous Hg (RGM) measurements collected at Thompson Farm located in Durham, NH over a 3 year time period. The duration of this study allowed for seasonal and inter-annual comparisons. Seasonally, Hg wet deposition …

Effects Of Nitrogen-Fixing Symbiotic Cyanobacteria On The Microbial Ecology Of The Coral, Montastraea Cavernosa, Jessica K. Jarett

Doctoral Dissertations

Corals form the physical structure of coral reefs, one of the most ecologically and economically important ecosystems in the world. The abundant and broadly distributed Caribbean coral Montastraea cavernosa forms a symbiosis with intracellular nitrogen-fixing cyanobacteria in some, but not all colonies, which make up approximately 30% of the population and display a characteristic orange fluorescence. Diverse and functionally important microbial communities of dinoflagellates, bacteria, Archaea, viruses, fungi, and other organisms are also associated with corals and together with the host compose what is termed the coral holobiont. Whether the cyanobacteria are mutualists, commensals, or parasites, and their effects on …

Throughfall Chemistry In Deciduous And Coniferous Forest Stands At Thompson Farm, New Hampshire, Musa Dinc

Master's Theses and Capstones

In this study, I compare the chemical composition of throughfall in deciduous and coniferous forest stands to the chemistry of wet deposition. The study was conducted at Thompson Farm, Durham NH, which is owned and managed by the University of New Hampshire. Thompson Farm (43.11N, 70.95W) is at an altitude of 23 m and about 24 km from the Gulf of Maine. Throughfall samples were obtained from two forest stands using wet-dry Aerochem Metrics 301 collectors and rainfall samples were collected in a wet-only precipitation collector (N-CON Atmospheric Deposition Samples Model 00-120) from 14 April 2009 to 14 November 2009.The …

Ecosystem Structure And Function In An Urban, Piped Stream, Amanda Hope

Master's Theses and Capstones

Piped streams, or streams that run underground, are common features in urban areas. However, there is little empirical evidence regarding their ecological structure and function. This study measured ecosystem metabolism, nutrient uptake, and related characteristics of Pettee Brook -- an urban stream that flows through several pipes under impervious surfaces near the UNH (Durham) campus.

Piped and open reaches of Pettee Brook had similar water quality, nutrient uptake, and ER. However, the absence of light in piped reaches led to their complete loss of GPP. Benthic AFDM and chlorophyll a biomass were also significantly reduced in piped reaches. For both …

Dissolved Organic Carbon Quantity And Quality In North American Rivers And Streams, Kevin Walker Hanley

Master's Theses and Capstones

The controls on the quantity and chemical composition of dissolved organic carbon (DOC) in freshwater systems are crucial to understanding and managing processes like carbon sequestration, heavy-metal transport, and municipal water sanitization. We analyzed DOC quantity and quality for 17 major North American rivers and the temporal variability of DOC quantity and quality in several thousand small basins. Among large basins, we found positive correlation between wetland-cover and both DOC concentration (R²=0.78; p<0.0001) and specific ultraviolet absorbance at 254nm (SUVA254; R²=0.91; p<0.0001). We found that the role of river networks in altering the annual DOC signal minimal except in systems with long residence times. Among small basins, we found characteristics like runoff, stormflow, and vegetation indices useful in predicting the temporal variability of DOC concentration. Further work should clarify where individual characteristics drive DOC variability and more rigorously define the role of processing in large rivers.

Investigation Of Chromophoric Dissolved Organic Matter As A Freshwater Tracer In The Kennebec River Estuary, Alison Barner

Master's Theses and Capstones

In an attempt to explore the feasibility of using chromophoric dissolved organic matter (CDOM) as a freshwater tracer in the Kennebec Estuary of Maine, potential causes of the variability of the CDOM absorption coefficient (ag412) in relation to salinity were investigated. A predictable relationship between CDOM variability and factors such as river discharge and season was sought to explain CDOM variability for use in remote sensing. To accomplish these objectives, ag412 was calibrated to continuous underway FDOM measurements using linear regressions from 14 cruises. USGS daily discharge rates were checked for possible relationships with ag412 values. Although no trends were …

Hydrogen Dynamics In Soil In Northern Boreal And Subarctic Sweden, Kaitlyn J. Steele

Master's Theses and Capstones

Molecular hydrogen (H2) is produced and consumed through syntrophic organic matter decomposition in soil. The purpose of this study was to determine if organic-rich soils can become a temporary source of H2 to the atmosphere under anoxic conditions and the release of labile carbon.

H2 was generally consumed at the subarctic peatland, but the net H2 uptake decreased as site moisture increased from the dry palsa site to the wet Eriophorum site. The dissolved H 2 concentrations suggest that methanogenesis is the predominant decomposition pathway at depth and other decomposition processes or plant-mediated transport influence concentrations closer to the surface. …

Controls On Variability Of Dissolved Greenhouse Gas Concentration And Emissions From Small Streams In Southeastern New Hampshire, Jason Baillio

Master's Theses and Capstones

Small streams often present the first opportunity for dissolved greenhouse gases to exchange with the atmosphere and can be potential hot spots for evasion. In this study three streams in southeastern New Hampshire representing differing landuse were monitored for emissions of nitrous oxide, methane, and carbon dioxide. Average emission rates of N2O varied from -84 mug N m-2 day-1 to 2,561 mug N m-2 day-1 and correlated strongly with NO 3- concentration. One stream, Rum Brook, was found to be a net sink for N2O from the atmosphere. Methane emissions varied from 1.1 mg C m-2 day-1 to 21 mg …