The Role of Hg(II) Reduction and Chemical Speciation in Controlling the Concentration of Mercury and its Methylation in Natural WatersEPA Grant Number: R824778
Title: The Role of Hg(II) Reduction and Chemical Speciation in Controlling the Concentration of Mercury and its Methylation in Natural Waters
Investigators: Morel, Francois M.
Institution: Princeton University
EPA Project Officer: Hiscock, Michael
Project Period: November 1, 1995 through October 31, 1998 (Extended to October 31, 1999)
Project Amount: $349,950
RFA: Water and Watersheds (1995) Recipients Lists
Research Category: Water and Watersheds , Water
Description:According to our understanding of the mercury cycle in natural waters, two distinct processes determine the rate of formation of methylmercury and its eventual accumulation in fish: 1) mercury reduction and volatilization control the overall concentration of mercury in many natural water bodies; 2) mercury uptake and methylation by bacteria control the transformation of inorganic mercury into its biologically accumulated organic form. The ultimate aim of this project is to elucidate the parameters that control the concentration and bioaccumulation of methylmercury.
Building on the preliminary research described in the proposal to EPA/NSF, rapid progress has been made on both the chemical and microbiological aspects of the project. In particular, the rates of oxidation and reduction of dissolved mercury and the rate of dissolution of mercuric sulfide under various conditions have begun to be quantified. Contrary to what is generally reported in the experimental literature, the oxidation of Hg(0) in oxic waters is relatively rapid (hours to days). This process, should effectively decrease the net rate of Hg(0) volatilization and maintain higher mercury concentrations in many aquatic systems.
In addition, preliminary data have been obtained in support of the hypothesis that the presence of polysulfides increases the solubility of mercury sulfide and enhances many fold the rate of microbial methylation of mercury under anoxic conditions. If these preliminary results are confirmed, they will constitute a breakthrough in our understanding of the mechanisms of Hg methylation in anaerobic sediments and of the factors that control it.