150 years of anthropogenic metal input in a Biosphere Reserve: the case study of the Canan,ia-Iguape coastal system, Southeastern Brazil

The Canan,ia-Iguape system consists of a complex of estuarine and lagoonal channels located in the coastal region of southeastern Brazil known as Lagamar, a Biosphere Reserve recognized by the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 1991. The area suffered dramatic environmental changes along the last ca. 150 years initiated by the 1852 opening of an artificial channel, the Valo Grande, connecting the Ribeira de Iguape River to the estuarine system. Due to Au, Ag, Zn, and Pb mining activities that took place in the upstream regions of the Ribeira de Iguape River since the seventeenth century, the system has acted as a final destination of contaminated sediments. Analysis of cores located along the estuarine system revealed a history of contamination, with an increase of anthropogenic metal input between the decades of 1930 and 1990. The anthropogenic influence can be traced in locations as far as 20 km from the mouth of the artificial channel.