MERCURY DISTRIBUTION IN SEDIMENT PROFILES FROM LAKES OF THE HIGH PANTANAL, MATO-GROSSO STATE, BRAZIL

Sediment cores from lakes located in the Pantanal Swamp, Central Brazil were analysed for the distribution of mercury released by the local gold mining. Atmospheric transport is the only pathway of mercury contamination of these remote lakes. Mercury concentrations were higher at the surface of sediments (62 to 80 ug.kg-1) decreasing to values of 20 to 30 ug.kg-1 in deeper layers. Mercury deposition rate was estimated as 90 to 120 ug Hg.m-2.yr-1. Although mercury concentrations were much lower than in industrialized areas, mercury deposition rate for these Pantanal lakes is of the same order of magnitude of deposition rates measured in lakes in industrialized areas.