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THE MODELING OF THE FATE AND TRANSPORT OF ENVIRONMENTAL POLLUTANTS
Citation:
Betowski, L D., M. Enlow, L A. Riddick, T W. Collette, AND J. C. D'Angelo. THE MODELING OF THE FATE AND TRANSPORT OF ENVIRONMENTAL POLLUTANTS. Presented at Devils's Hole Workshop and Death Valley Regional Flow Model, Death Valley, CA, May 22, 2003.
Impact/Purpose:
The overall goals of the task are to apply NERL's core capability in advanced chemical science and technology for maximum benefit in estimating exposures of ecosystems and humans to chemical stressors and to identify emerging pollution concerns, in particular long-range airborne transport of contaminants. This task comprises several subtasks, each with individual objectives:
Subtask 1: screen exposures of National Park PRIMENet ecosystems to chemical stressors, identifying indications of exposure requiring further evaluation, and use these samples evaluate new analytical methods as replacements for standard methods in future assessments of ecosystem contaminant exposures.
Subtask 2: evaluate a new mercury analytical approach with superior performance on complex solid matrices such as biological tissues, and apply the approach to estimating exposure of ecosystems and humans to mercury.
Subtask 3: determine distribution patterns of chemical contaminants in the southern Sierra Nevada Range of California, investigate topographic and weather factors that may influence the distributions, and determine if a correlation exists between contaminant distributions and extirpation patterns of the mountain yellow-legged frog.
Subtask 4: provide analytical methods to measure a number of inorganic and organic arsenic species in a variety of environmental matrices, elucidate the environmental transformations undergone by organoarsenic animal-feed additives, and determine if the potential exists for substantially increased exposure of humans and aquatic organisms to arsenic.
Description:
Current models that predict the fate of organic compounds released to the environment are based on the assumption that these compounds exist exclusively as neutral species. This assumption is untrue under many environmental conditions, as some molecules can exist as cations, anions, zwitterions, or neutrals, depending on pH. Computational methods can assist in the improvement of these models by simulating the Raman spectra of a particular species. This is accomplished through frequency calculations using quantum mechanical programs like Gaussian, which calculates energies of compounds based on their molecular structures. These calculations give information about the frequency and motion/direction of the vibration. Researchers are able to use this data as a tool to help predict the measurement of simultaneously occurring species of environmental pollutants at varied temperatures and pH. A direct comparison is made between the calculated Raman frequencies and the experimental frequencies for four microspecies of meta-hydroxypyridine.