Cadmium, Lead and Manganese in tidal flats sediments of the Bahía Blanca estuary, Argentina

BOTTÉ, S.E.; DELUCCHI, F.; GRECCO, L.E.; MARCOS, A.O.; FREIJE, R.H.; MARCOVECCHIO, J.E.

Buzios/Rio de Janeiro, Brasil

Simposio; 4th International SYMPOSIUM ENVIRONMENTAL GEOCHEMISTRY IN TROPICAL COUNTRIES; 2004

Departamento de Geoquímica da Universidade Federal Fluminense

Many chemical pollutants, between them heavy metals, are commonly associated with fine particles dissolved. In addition, much of processes that occur in estuaries are related, al least in part, with input, output, transport and distribution of sediment. The geomorphologic characteristics of these environments favor settling on tidal flats. Bahía Blanca estuary concentrates several urban centers, a large industrial nucleus, one of the more important deep harbor systems from country and presents a very extensive agricultural-livestock area. So, the terrestrial drainage, the urban and industrial wastes and the permanent dredging of channel navigation, act as source of dangerous elements for the system. The transference of initially deposited and immobilized substances to bioavailable compounds should produce negative effects on the ecosystem. Such reasons bring us to determine the concentration and distribution of many heavy metals, which could be occur naturally or not on sediments from tidal flats. Since June 2000 nine metals have been studied in tidal flats superficial sediment and pore-water, in sub-superficial water and in salt marsh plants, in three different sites on the inner zone of the estuary with monthly frequency. In the present work are showed the results of twenty sediments samples analyses for cadmium, lead and manganese, which were collected with plastic equipment at depths not upper 20-30 cm. Before of the 48h the samples were drying, homogenized and storage until analytical treatment. On one of them and for each station granulometric analysis was performed. In two campaigns were separated sub-samples to obtain the fraction minor 63 mm (silt-clay). Total metal concentrations were determined following the method reported by Daziel & Baker (1983) and modified by Marcovecchio et al. (1988) which consist in a web mineralisation with an acids mix to controlled temperature. Furthermore, to determine the geochemical partitioning was applied a sequential extraction method described by Megalatti et al. (1983) and modified by Lacerda et al. (1988) and Maddock & Lopes (1988). All corresponding metal concentrations were measured by atomic absorption spectrophotometry (AAS) with air-acetylene flame on a Perkin Elmer 2380 Spectrophotometer.