Especiación de Pb, Zn y Fe en sedimentos intermareales de la ensenada de San Simón (parte interna de la Ría de Vigo, NO de España)

Resumo

Metal spéciation of Pb, Zn and Fe was determined in intertidal sediments of San Simon Bay in order to study metal bioavailability and diagenetic processes. The most important fractions for Zn and Fe were those bound to Fe-Mn oxihydroxides and to organic matter-sulphides, while for Pb it was the residual one. The results showed that the most labile fractions were bound to exchange sites of organic matter and clays, and these fractions were important for Pb and Zn. Fe concentrations were used as an indicator of diagenetic processes that were detected by the presence of redox levels in the sediments. These levels were reflected in the concentration profiles by a succession of maximum and minimum values and in the field, by a sequence of blackish and reddish levels. Principal Components Analysis separated different behaviours between the studied fractions related to their mobility, antropogenic influence and redox boundary level. Pb and Zn were related to an antropogenic origin while Fe concentrations reflected their lithogenic origin.