Chemical characterization and 210Pb dating in wetland sediments from the Nhecolandia Pantanal Pond, Brazil

Pantanal, located in the central region of South America, is recognized as one of the world's largest freshwater wetlands. In order to verify possible changes in this environment, a study was undertaken in Nhecolandia Pantanal, Mato Grosso do Sul State, Brazil. Two sediment cores from the Salina do Meio pond (SM1 and SM2) and one core from a small flood land named Ba (B5) were collected in 2001. The elements As, Ba, Br, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb, Zn and Zr were determined by instrumental neutron activation analysis (INAA). Cluster and factorial analysis were applied to the chemical data. The sedimentation rate in the SM2 core was determined by 210Pb method and the mean value found was 0.61 cm x y-1. The results obtained in the present study showed that recent geochemical processes such as desorption, precipitation and dissolution can contribute for the high water alkalinity and salinity in the saline ponds. (author)