Relationship of mercury with aluminum, iron and manganese oxy-hydroxides in sediments from the Alto Pantanal, Brazil

Sediments from nine floodplain lakes in Pantanal were analyzed for a large-scale 300 km. survey of mercury Hg. load in sediments and soils of the Alto Pantanal and to study the relationship between Hg and reactive aluminum, iron, and manganese oxy-hydroxides. The results were compared with the Hg content in river and stream sediments from the Pocon´e gold mining area, where Hg has been extensively used and still is in use. The results indicate that the Hg concentrations were elevated in river sediment close to the mining area in Bento Gomes river basin average in the -74-mm fraction 88.9 ng Hg gy1 dry wt.; interquartile range 50.3]119.5., but there was no clear indication that the local Hg emissions have contaminated the remote floodplain lakes, where concentrations were surprisingly low average in the -74-mm fraction 33.2 ng Hg gy1 dry wt. sediment; interquartile range 18.4]46.8., in particular when considering geochemical characteristics of the sediment. The sediment from the floodplain lakes contained less Hg-tot and more reactive iron oxy-hydroxides than soils from the Tapaj´os area in the Amazon basin. This resulted in a mass ratio between Hg and amorphous oxy-hydroxides of only 5=10y6 for Hg-totrFe-oxa interquartile range 3]7=10y6 ..