Trace metal concentrations in coastal marshes of the Lower Paraná River and the Río de la Plata Estuary

Abstract

Cu, Cr, Pb, Zn and Fe in water, sediment and tissue of the emergent macrophyte Schoenoplectus californicus were studied in three coastal environments differing in aquatic chemistry and tide amplitude: a deltaic floodplain marsh, a coastal vegetated strip of the river and a tidal marsh at the south margin of the Rio de la Plata Estuary. Metal content in water was not significantly different between the river and the floodplain marsh. Metal content in sediments showed higher values in the marshes than in the river, suggesting a retention in the marsh. Except for Cu, the highest metal content in sediments and water was observed in the tidal marsh. Pb in plants was undetectable. Metal content was higher in rhizomes, except Cr, which was mainly stored in stems. Rhizome metal content was higher in the river, probably related to the higher redox potential of its sediments. Inflorescence metal content was higher in the marshes: the highest Zn, Cr and Fe contents were measured in the tidal marsh; the highest Cu content was in the floodplain marsh, together with the highest organic matter content of the sediments. Zn, Cr and Fe increased in standing drying stems and in inflorescences in late fall. Inflorescences showed the highest metal content after seeds had been released.