IS TOTAL MERCURY CONCENTRATION A GOOD PREDICTOR OF METHYL MERCURY CONCENTRATION IN AQUATIC SYSTEMS

Methyl mercury (MeHg) concentrations were compared to total mercury (T Hg) concentrations in a variety of types of aqueous samples collected at the Experimental Lakes Area during 1991 through 1993. In several st reams, an experimentally flooded wetland, and peat pore water, there w as no relationship between MeHg and THg concentrations. %MeHg(compared to THg) ranged from <1% to over 90%. In three ELA lakes, as in groups of lakes from other regions, a linear relationship between MeHg and T Hg concentration was found. However, these relationships differed by a factor of three from one region to another. This study shows that THg inputs and/or concentrations are not very useful in predicting MeHg c oncentrations, and that factors within ecosystems are very important i n controlling MeHg concentrations.