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The Roles Of Tidal Marshes In The Estuarine Biochemical Processes: A Numerical Modeling Study, Xun Cai

VIMS Articles

Observations suggest that the existence of tidal marsh can alter the oxygen and nutrient dynamics in adjacent water bodies, but assessing the impacts of large tidal marshes on an estuary is challenging. In this study, we use a modeling approach to investigate the roles of tidal marshes on the estuarine biochemical processes. The marsh model, which simulates the ecological functions of marshes at seasonal and annual time-scales, is embedded inside an unstructured-grid three-dimensional hydrodynamic and eutrophication model (SCHISM-ICM). This modeling system simulates the growth and metabolism of the tidal marshes and links biological processes to nutrient dynamics in the water …

Chemical Analysis Of Organic Compounds In Dew Water, Monica Dibley

Undergraduate Honors Theses

Water films on outdoor surfaces, such as dew, can act as a reservoir for organic molecules deposited from the atmosphere and they present a potential reactive medium for chemical transformations. To better understand the flux of volatile organic compounds from evaporating films, the composition and reactivity of the complex mixture of dissolved organic material (DOM) found in these films need to be characterized. Previous studies have measured the salts and the small organic molecules in dew collected on clean Teflon surfaces or condensers. Here, we expand on this by probing the organic chemicals found on natural outdoor surfaces covered in …

Honey As A Biomonitor For Air Pollutant Deposition In The Eastern United States Using Ion Chromatography And Scanning Electron Microscopy, Cole Cochran

Undergraduate Honors Theses

Anthropogenic activities generate metal, acid, and particulate air pollutants which negatively impact human and ecological health. In the United States, power plant, industrial, and vehicle emissions are leading causes of air pollution, however, the measurement of air pollution at high-resolution spatial regimes remains a challenge. Honey has emerged as a powerful biomonitoring tool to effectively quantify contaminants without the need for a large array of monitoring instruments. I hypothesized that honey could be used to effectively measure and map modern air pollutant spatiotemporal relationships over the Eastern U.S. Using ion chromatography with sulfate as an indicator for air pollution and …

Molecular Cluster Fragment Machine Learning Training Techniques To Predict Energetics Of Brown Carbon Aerosol Clusters, Emily E. Chappie

Undergraduate Honors Theses

Density functional theory (DFT) has become a popular method for computational work involving larger molecular systems as it provides accuracy that rivals ab initio methods while lowering computational cost. Nevertheless, computational cost is still high for systems greater than ten atoms in size, preventing their application in modeling realistic atmospheric systems at the molecular level. Machine learning techniques, however, show promise as cost-effective tools in predicting chemical properties when properly trained. In the interest of furthering chemical machine learning in the field of atmospheric science, I have developed a training method for predicting cluster energetics of newly characterized nitrogen-based brown …

Isotopes In The Estuary: Conception And Application Of Stable And Radioactive Carbon, Derek Detweiler

Reports

Grades: 9-12 Subjects: Chemistry | Environmental Science | Oceanography

In this interactive estuary-focused activity, students will examine stable and radioactive isotope data which provide information about the source and age of environmental samples such as plant and soil matter. Students will calculate average isotope ratios from five reference land types (forest, wetland, agriculture, industry, aquatic) and an unknown site within an estuary. Students will graph their calculated ratios and determine the land type that most impacts their estuary based on reference-to-unknown comparisons.

Numerical Simulations Of The Biogeochemical Impact Of Atmospheric Nitrogen Deposition On Surface Waters Of The Western North Atlantic, Pierre St-Laurent, Marjorie A.M. Friedrichs

Data

The impacts of atmospheric nitrogen deposition on the chlorophyll and nitrogen dynamics of surface waters in the western North Atlantic (25-45N, 65-80W) were examined with a biogeochemical ocean model forced with a regional atmospheric chemistry model. The model simulations cover the period 2004 to 2008 and are fully described in the following reference: St-Laurent, P., et al., Impacts of atmospheric nitrogen deposition on surface waters of the western North Atlantic mitigated by multiple feedbacks, J. Geophys. Res. Oceans, vol.122, doi:10.1002/2017jc013072.

Modeling Distinct Vertical Biogeochemical Structure Of The Black Sea: Dynamical Coupling Of The Oxic, Suboxic, And Anoxic Layers, T Oguz, Hw Ducklow, P Malanotte-Rizzoli

VIMS Articles

A one-dimensional, vertically resolved, physical-biogeochemical model is used to provide a unified representation of the dynamically coupled oxic-suboxic-anoxic system for the interior Black Sea. The model relates the annual cycle of plankton production in the form of a series of successive phytoplankton, mesozooplankton, and higher consumer blooms to organic matter generation and to the remineralization-ammonification-nitrification-dentrification chain of the nitrogen cycle as well as to anaerobic sulfide oxidation in the suboxic-anoxic interface zone. The simulations indicate that oxygen consumption during remineralixation and nitrification, together with a lack of ventilation of subsurface waters due to the presence of strong stratification, are the …

Organic Carbon Abundance, Distribution And Metabolism At The Oyster, Virginia Study Site, Elizabeth Canuel, Iris C. Anderson, Craig Tobias

Reports

This report describes a pilot study conducted at the DOE Subsurface Science Program's study site in Oyster, VA. The objective of this study was to examine whether 2 organic matter associated with the solid and dissolved phases was labile enough to support microbial activity. Organic matter availability was assessed in two ways: (1) by quantifying the amount and distribution of total organic carbon (TOC) associated with the solid phase and (2) laboratory experiments to examine the utilization of dissolved organic matter by measuring total microbial respiration. In addition to assessing total respiration, we specifically addressed organic matter respiration via denitrification. …

Correlation Between Electron Capture Negative Chemical Ionization Mass Spectrometric Fragmentation And Calculated Internal Energies For Polychlorinated Biphenyls, John Greaves, Ellen Harvey, William G. Macintyre

VIMS Articles

Correlations between molecular structure and fragmentation observed in electron capture negative chemical ionization mass spectra (moderator gas = methane) of 49 selected tetrachlorinated, pentachlorinated, and hexachlorinated biphenyls have been investigated by using molecular modeling. The semiempirical general molecular orbital program MOPAC was used to calculate molecular properties for biphenyl and the 209 polychlorinated biphenyls. The mass spectrometric ionization and fragmentation processes were found to be linked to the number of chlorine atoms present on the biphenyl, and to the number of those chlorine atoms in the ortho (2, 2', 6, and 6') positions. The intensity of molecular ions increased with …

Determination Of Tributyltin In The Marine-Environment, Rg Huggett, Michael A. Unger, Fa Espourteille, Cd Rice

VIMS Articles

Tributyltin (TBT) is a biocide used in antifouling paints to protect hulls from nuisance organisms such as barnacles, worms and algae. The use of TBT paints has increased over the past decade due to its effectiveness as an antifoulant which is related to its toxicity. Water concentrations of less than 100 ng L- have been shown to harm some aquatic species in laboratory tests and observations in the natural environment indicate that levels below 10 ng L- may be harmful. Tributyltin is bioconcentrated by many species to levels of one thousand, or more, times ambient water concentrations. Sediment-water partitioning coefficients …

Hydrocarbon Fuel Chemistry : Sediment Water Interaction, William G. Macintyre, C. L. Smith, P. O. Defur, C. W. Su

Reports

The objective of this program was to determine the effect of sediments on aqueous solutions of selected United States Air Force (USAF} hydrocarbon fuels. Effects of sediment type, organic carbon content, pH, temperature and salinity on interaction of dissolved hydrocarbons with sediment were studied. The results of this work can be used to estimate the role of sediment hydrocarbon interaction terms in fate models of aqueous systems, such as the Environmental Protection Agency "EXAMS" model.

Distribution Of Ammonia Nitrogen In The Lower York River, Virginia : Spring, 1961, Bernard C. Patten, Virginia Fisheries Laboratory, Virginia Institute Of Marine Science

Reports

No abstract provided.