Evaluation of the extension and pollution history by metals and trace elements in river sediments: case study, Tietê River, State of São Paulo

Abstract

The Tiete river drains an area composed of six sub-basins (Alto Tiete, Sorocaba/Médio Tiete, Piracicaba-Capivari -Jundiai, Tiete/Batalha, Tiete/Jacaré and Baixo Tiete). Along its extension (1,100 km), its margins bathe 62 municipalities. In spite of all its historical contribution, hydroelectric potential and being one of the most economically important rivers in the state of São Paulo, the Tiete river is also one of the world's most polluted rivers, especially in the municipality of the city of São Paulo. As a result of pollution problems observed in the last few decades, the aim of this study is to evaluate the concentration of metals, major and trace elements in surface and core sediment samples, in 34 points from its source in Salesopolis until to the end, Parana river. For this purpose, the following analytical techniques and their respective elements analyzed will be applied: INAA: As, Ba, Br, Ca, Ce, Co, Cr, Cs, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn; XRF: major elements and loss of ignition; ICP OES: Ag, Al, Ba, Be, Co, Cr, Cu, Fe, Li, Mg, Mn, Mo, Ni, Sn, Sr, Ti, V and Zn; FG AAS: Cd and Pb and CV AAS, for total Hg. Also, in each core slice by radiochemical method, the radionuclides 226Ra and 210Pb will be determined, for sediment dating. The INAA results will be compared to the NASC reference values (North American Shale Composite) and regional basal values. The enrichment factor (EF) and geoaccumulation index (GI), to assess the presence of anthropogenic pollution sources, will be used. Metal concentrations obtained by ICP OES and AAS will be compared to TEL and PEL oriented values from CCME and adopted by CETESB. In addition, the concentration of oxygen, pH, conductivity and potential oxidation-reduction in the sediment and water samples from all sampling points will be determined. From this study, it will be possible to carry out a diagnosis of the Tiete river sediment quality (surface and cores), in all its extension, in the current days as well as in the past, directing for future corrective actions that can anticipate a greater damage to the quality of this important river. (AU)