Mercury modeling to predict contamination and bioaccumulation in aquatic ecosystems.

In response to increasing scientific evidence of the environmental toxicity of mercury and its organic compounds, this study reviews the state of knowledge about the mercury cycle in aquatic systems. It describes the aquatic chemistry of mercury and discusses the importance of biological and physicochemical parameters such as pH, temperature, dissolved organic carbon, oxygen concentration, mercury and methylmercury concentration and availability, as well as sulfate, manganese, and iron concentration in surfaced waters. There is still a paucity of information on environmental dependency of factors that regulate the formation, destruction, and trophic transfer of methylmercury. This lack has led to numerous studies to define the factors that can influence its bioconcentration and bioaccumulation. This review presents some alternative models for mercury cycling, speciation, and partitioning based on the trend toward "site-specific water quality standards," in which chemical speciation is considered on a site-by-site basis.