MODELING THE ELIMINATION OF MERCURY BY FISH

Mass balance models can be used to predict mercury accumulation in fis h. However, factors influencing mercury elimination, an essential para meter of the mass balance model, are poorly understood. We developed a general model of mercury elimination from fish using literature data. Our analysis showed that short-term experiments (<90 days) overestima ted the elimination rate of mercury and that inorganic mercury was exc reted 3-fold faster than methylmercury. Both inorganic mercury and met hylmercury excretion were negatively correlated to body size, but only methylmercury elimination was significantly correlated to water tempe rature. A general model of methylmercury excretion was developed using temperature, body size, and a dummy variable representing exposure ti me (acute vs chronic) as independent variables (r(2) = 0.77). Methylme rcury depuration rate was independent of mercury burden and concentrat ion, indicating that it is a first-order process. Methylmercury elimin ation tended to be overestimated by a factor of 2-6 by empirical model s that were published prior to this study. A field test showed that ou r model adequately estimated the elimination rate of methylmercury und er natural conditions.