A probabilistic analysis of regional mercury impacts on wildlife

We investigate the uncertainties associated with modeling the potential hea lth effects on piscivorous animals of mercury released to the atmosphere. T he multimedia modeling system combines an atmospheric fate and transport mo del, an aquatic cycling model, and a terrestrial food web model. First, the modeling system is used to calculate point values of the animals' hazard q uotients (i.e., measures of toxic dose). Next, we use a simplified version of the modeling system to conduct a probabilistic analysis for the Great La kes region that takes into account input uncertainty, variability, and unce rtainty and variability combined. The use of two different software package s for the combined uncertainty/variability analysis led to similar results except for high values (>90th percentile) where some differences were evide nt. A sensitivity study was performed on the combined uncertainty and varia bility analysis. Regional variability caused more than 70% of the variance in the results, with the fish bioaccumulation factor accounting for the maj ority of the variability. The major sources of uncertainty were the speciat ion of the mercury emissions, the lake pH, and the sediment burial rate.