Modeling the Elimination of Mercury by Fish

Abstract

Mass balance models can be used to predict mercury accumulation in fish. However, factors influencing mercury elimination, an essential parameter 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) overestimated the elimination rate of mercury and that inorganic mercury was excreted 3-fold faster than methylmercury. Both inorganic mercury and methylmercury excretion were negatively correlated to body size, but only methylmercury elimination was significantly correlated to water temperature.A general model of methylmercury excretion was developed using temperature, body size, and a dummy variable representing exposure time (acute vs chronic) as independent variables ( r 2 = 0.77). Methylmercury depuration rate was independent of mercury burden and concentration, indicating that it is a first-order process. Methylmercury elimination tended to be overestimated by a factor of 2−6 by empirical models that were published prior to this study. A field test showed that our model adequately estimated the elimination rate of methylmercury under natural conditions.