Retrospective study of mercury in raccoons (Procyon lotor) in south Florida.

Museum and recent collections of raccoon hair were used to assess whether temporal or spatial trends existed in MMHg distributions in south Florida. The hypothesis that MMHg in raccoon hair had remained the same since 1947 could not be rejected. Some sampling regions showed increases while others did not. However, large differences existed between sites, amounting to a factor of 20 for raccoons collected during 2000 and during the period prior to 1960 (museum samples). Raccoon feeding behavior and the production of MMHg most probably accounted for the spatial differences. Large differences in MMHg concentrations existed in different tissues ranging in order of hair, liver, kidney, muscle, heart, brain, and blood in their respective ratios to blood: 96:10:6:5:4:2.5:1. Liver Hg is 7% MMHg, while hair Hg is 99% MMHg. These associations appear largely regulated by metabolic processes. Speciation of Hg is very important for gaining an understanding of ecosystem and organism Hg dynamics. Further work is needed to establish whether Se plays a role in Hg sequestration and whether hair Hg is a good surrogate for estimating Hg concentrations in other tissues in south Florida raccoon populations.