Neutron activation analysis applied in sediment samples from the Guarapiranga Reservoir for metals and trace elements assessment.

The Guarapiranga Reservoir is a very important aquatic system due to the fact that it is one of the main water reservoirs for South America's largest city, São Paulo, Brazil. Guarapiranga basin is located within the Metropolitan Region of São Paulo and the reservoir itself is located in the Northern part of the basin occupying approximately 26 km. This reservoir is characterized by environmental impacts from urban invasion, industrial and sewage wastes, all of which seriously affect its water quality and, consequently, the sediment quality. Two collection campaigns were undertaken: April 2009 and June 2010. The samples were analyzed by instrumental neutron activation analysis (INAA) in order to determine the following elements: major (Fe, K and Na), trace (As, Ba, Br, Co, Cr, Cs, Hf, Rb, Sb, Sc, Ta, Tb, Th, U and Zn) and rare earths (Ce, Eu, La, Lu, Nd, Sm, Tb and Yb). The organic matter and granulometric distribution were also evaluated and multivariate analysis was applied to the results. The study of elemental ratios indicated that the amount of elements present in the Guarapiranga Reservoir is mainly of detrital origin. [ABSTRACT FROM AUTHOR]