Metal, trace and rare earth elements assessment in a sediment profile from Taiaçupeba Reservoir, São Paulo state, by INAA

Abstract

The Taiaçupeba reservoir is located on the border of Mogi das Cruzes and Suzano counties and composes the Alto Tietê Producing System (SPAT). The region shows high population density and industrial production, which cause waste and contaminants generation, which can affect the water supply quality. The purpose of this study was to evaluate the concentration and distribution of As, Ba, Br, Co, Cr, Cs, Fe, Hf, K, Na, Rb, Sb, Sc, Ta, Th, U, Zn and the rare earth elements (Ce, Eu, La, Lu, Nd, Sm, Tb and Yb), present in a sediment profile collected in the Taiaçupeba reservoir. Sampling was performed in 2016 by CETESB for monitoring purposes. Instrumental Neutron Activation Analysis technique was applied for multilemental determinations. A great variation of the concentration for the elements analyzed along the sediment profile was observed, with a concentration peak in the depth of 20cm for all elements and decreasing in the deepest slices. Enrichment factor (EF) and Geoacumulation Index (IGeo) tools used to evaluate the presence of anthropogenic pollution sources indicated As and Zn contamination, mainly in the more recent sediment samples (from 0 to 5 cm depth). When the concentration values for As, Cr and Zn were compared to TEL and PEL for quality sediment evaluation, none of the concentration values for As and Cr surpassed the PEL values but not Zn. The results showed that an important anthropogenic contribution for As, Cr and Zn in the upper layers of the sediment core is occurring.