Mercury in the Moji-Guacu River Basin, S.P—Brazil: The Link between Marginal Lagoons and River Contribution, Assessed by ~(210)Pb Dating Profiles

摘要

Total mercury content was evaluated in water and suspended sediment samples of the Moji-Guacu river and in water and bottom sediment of its 3 marginal lagoons (Catingueiro, Barrinha, and Rio das Pedras), located down-stream of the sampling point in the main channel. In all situations, low Hg concentrations were found in suspended and bottom sediments. Aluminum was used as a geochemical tracer to normalize the Hg concentrations in the sediment cores from the Rio das Pedras lagoon (r = 0.92). It was estimated that the Moji-Guacu river transports up to 19 kg Hg yr~(-1), 65% in the dissolved form and 35% adsorbed onto particulate matter. Following an acute toxic stage observed in the years 1970-1980, the basin has been restored to its original conditions mainly by natural recovery and a general reduction in Hg input to the ecosystem.