Hudson, R. J.M.. University of Illinois, rjhudson@uiuc.edu
Watras, C. J.M.. Wisconsin Department of Natural Resources, cjwatras@facstaff.wisc.edu

 
METHYLMERCURY UPTAKE BY FRESHWATER MICROORGANISMS: MODELING SESTON-WATER PARTITIONING DATA FROM WISCONSIN LAKES
 
Methylmercury uptake at lower trophic levels is the major step in the biomagnification of this microcontaminant. Passive uptake of neutral monomethylmercury (meHg) chloride and hydroxide species must occur in all aquatic organisms. However, it remains to be seen whether it is the dominant mechanism for meHg uptake by freshwater microorganisms. The possibility that accidental uptake via a facilitated transport process also occurs at significant rates was examined by analyzing observations of the seston-water partitioning of meHg from Wisconsin lakes with widely varying pH, DOM and chloride concentrations. Our approach was to formulate multiple mechanistic models for the uptake of meHg by seston, each with different assumptions concerning which chemical species control the uptake rates. These uptake models were coupled to a common chemical model of meHg complexation by natural DOM, chloride, and hydroxide ligands. Optimal values of the uncertain parameters in each model were obtained by fitting the field data. There were significant differences in the models' fit to the data. Our results indicate that both facilitated and passive uptake may be necessary in order to explain the Wisconsin field observations for meHg in seston as well as in fish.
 
Day: Friday, Feb. 5
Time: 02:00 - 02:15pm
Location: Sweeney Center
 
Code: CS63FR0200S