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THE ROLE OF AQUEOUS THIN FILM EVAPORATIVE COOLING ON RATES OF ELEMENTAL MERCURY AIR-WATER EXCHANGE UNDER TEMPERATURE DISEQUILIBRIUM CONDITIONS
Citation:
Loux, N T. THE ROLE OF AQUEOUS THIN FILM EVAPORATIVE COOLING ON RATES OF ELEMENTAL MERCURY AIR-WATER EXCHANGE UNDER TEMPERATURE DISEQUILIBRIUM CONDITIONS. Presented at Georgia Water Resources Conference, Athens, GA, March 26-27, 2001.
Impact/Purpose:
This research project sets out to design and conduct an assessment of the long-term ecological consequences of alternative management choices. As the first project to be done at this scale using predictive ecological endpoints, we will seek to identify the appropriate components of such an analysis. We will use experience gained in the conduct of this BASE analysis to identify key research and data needs for address, to estimate timing, resource needs, etc., for future analyses. We will extend this analysis beyond previous and ongoing studies in two ways: by incorporating biological endpoints, primarily properties of fish communities, and by introducing the concept of sustainability of ecological state under future scenarios contrasted with the present state of those same ecological resources. Requirements that are identified during the course of this study will permit the recommendation of specific capabilities that should be incorporated in a general modeling system currently under development to support BASE and other environmental assessments. Finally, the analysis is intended to be of value for establishing environmental management choices that will be beneficial and those that would be detrimental to the sustainability of ecological resources of the Albemarle-Pamlico Basin.
Description:
The technical conununity has only recently addressed the role of atmospheric temperature variations on rates of air-water vapor phase toxicant exchange. The technical literature has documented that: 1) day time rates of elemental mercury vapor phase air-water exchange can exceed nightinie rates by a factor of 2 to 3, 2) diurnal air-water exchange rates for PCBS (a conservative tracer for dynamic environmental elemental mercury) can exceed nocturnal rates by 44%, and 3) atmospheric vapor phase organic compound and elemental mercury concentrations can be correlated with atmospheric temperatures.
Loux (2000) developed a model for quantifying elemental mercury air-water exchange rates under variable atmospheric temperature conditions. Utilizing the two layer thin film exchange paradigm, the model is designed to estimate exchange rates under quiescent, low wind speed conditions. An assumption in this effort was that the temperature of the thin aqueous film dominating mercury vapor air-water exchange equals the atmospheric temperature. V;hUe this assumption is plausible under conditions of very low wind speeds and/or near 100% relative humidity, what effect would evaporative cooling have on the aqueous phase mass transport coefficient? Specifically, will evaporative cooling have a significant effect on rates of elemental mercury air-water exchange? This and other issues will be addressed.