Determination of uranium and thorium in sediments from Cananeia-Iguape system, Brazil

The Cananeia-Iguape system is a complex of lagoon and estuarine channels located in the south of state of Sao Paulo. This system received the waters of Ribeira de Iguape River, after the construction of a channel in 1852, which changed its original characteristic. This study evaluated the uranium and thorium concentrations in superficial bottom sediments samples from this system by spectrophotometric determination. The mean uranium concentration found was 2.9 mg kg^-1 and 6.6 mg kg^-1 for thorium. Geo-accumulation index classified the sediments as 'unpolluted to moderately polluted'. Statistical analysis showed that uranium and thorium presented a non-homogeneous behavior along the system. (author)