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THE EFFECT OF SALINITY ON RATES OF ELEMENTAL MERCURY AIR/WATER EXCHANGE
Citation:
Loux, N T. THE EFFECT OF SALINITY ON RATES OF ELEMENTAL MERCURY AIR/WATER EXCHANGE. Presented at International Workshop on Trends and Effects of Heavy Metals in the Arctic, McLean, VA, June 18-22, 2001.
Impact/Purpose:
To improve the scientific understanding of the linkage between fish methylmercury and ambient mercury in the environment.
To complete a model for transformation and bioaccumulation of mercury than can be linked with models for atmospheric deposition and hydrology to yield a multimedia integrated modeling system capable of quantifying regional exposure to mercury.
To apply state of the art modeling to assess ecosystem interactions with exposures to mercury for impacted aquatic ecosystems (e.g., wetlands, lakes, rivers, estuaries) including spatially distributed (GIS-based) modeling of watersheds, lakes and rivers.
Description:
The U.S. EPA laboratory in Athens, Georgia i spursuing the goal of developing a model for describing toxicant vapor phase air/water exchange under all relevant environmental conditions. To date, the two-layer exchange model (suitable for low wind speed conditions) has been modified to account for the effects of environmental temperature disequilibrium conditions and evaporative cooling on rates of elemental mercury air/water exchange (Loux, 2000; Loux, 2001a; Loux, 2001b). One (of many) issue(s) remaining to be addressed in this effort includes the effect of salinity on elemental mercury air/water exchange rates.
Elemental mercury exists as an uncharged dissolved gas when present in aqueous solution. As such, it is reasonable to expect the aqueous solubility of mercury to be sensitive to the same salting out phenomena observed with other neutral dissolved gaseous species. A traditional approach for quantifying the effect of salinity on solubility is the Setchenov relationship; a Setchenov relationship for elemental mercury was derived from data published in the peer-reviewed technical literature and its significance to air/water exchange rates in a previously simulated system was assessed to be less significant than: 1) diel variations in water column Hg concentrations, 2) diel variations in air/water temperature disequilibrium conditions, and 3) the effects of evaporative cooling on air/water exchange rates.