Sedimentary speciation of U and Th isotopes in a marsh area at the southwest of Spain

Abstract

A study of the distribution of U and Th-isotopes in different fractions of intertidal sediments collected in a marsh area has been carried out. This marsh area is affected by the releases of natural radionuclides from fertilizer industries carried out into the Odiel river. The study has shown that uranium is mainly located in non-residual fractions of the sediments and particularly coprecipitated with amorphous ferromanganese oxyhydroxides. In the case of Th isotopes, the contribution of residual fractions is higher than that of non-residual fractions, being the main non residual fraction again the amourphous ferromanganese oxyhydroxides. However, all fractions seems to reflect the same pattern of contamination. Thus, those sediments located along the Odiel river basin have the higher concentration in all sequentially extracted fractions. Some interesting activity and mass ratios have also been investigated.