Occurrence and spatial distribution of metals in intertidal sediments of a temperate estuarine system (Bahía Blanca, Argentina)

Abstract

Intertidal sediments of the inner and middle zonefrom the Bahı´a Blanca estuary were sampled for geochemicaland environmental assessment of metals (Cd, Cu,Pb, Zn, Mn, Ni, Cr and Fe). Results indicate that both theorganic matter content and the sediment grain size plays animportant role in controlling the differential concentrationsof the metals found in sediments from both zones. For mostof the elements (except Mn), sediment metal concentrationswere greater in the middle zone, although the concentrationsdid not exceed the maximums for quality ofmarine sediments. In this sense, anthropogenic impact (i.e.,sewage drain) appears to be a key factor in the distributionof metals within the estuarine system. Comparing the levelsobtained with quality levels (LEL and SEL), except Cu thatshowed levels slightly above the LEL, the rest of theconcentrations of metals were lower to those levels. Thelow metal concentrations obtained within this highlyimpacted estuarine system suggest that the great volume ofwater that flooding the extensive flats in each tidal cyclehas much importance. Although the potential risks ofmetals to the estuarine environment were low, taking intoaccount the toxicity of some of these metals, continuity ofmonitoring is highly recommended.