PARTICULATES AND THE ENVIRONMENTAL CAPACITY FOR TRACE-METALS - A SMALL RIVER AS A MODEL FOR A LAND-SEA TRANSFER SYSTEM - THE RASA RIVER ESTUARY

The paper deals with the role of particulates in the transfer of trace metals from land to sea. In the mechanisms oriented research, small r ivers and their estuaries fulfil a special role by enabling identifica tion of single processes and single transport mechanisms of general re levance to global land-sea interaction. In big rivers the complexity a nd the overlapping influences often prevent identification of these. L aboratory experiments often defy natural conditions. Small rivers, ori ginating from identifiable and often unique geological regions, with a limited number of anthropogenic activities loading their watersheds, offer a real-life model system for studies of physical and physicochem ical processes. The result of field work in the Rasa River (Croatian A driatic) karstic estuary and corollary laboratory experiments have sho wn the sedimentation pattern with the prevalent accumulation of terrig enous material in the upper estuary. The results indicate that trace m etals are either of prevalently natural origin (Cr, Ti, Cd) or anthrop ogenically superimposed (Cu, Pb, Zn). However, most of the heavy metal s accumulate in the proximity of the river mouth due to adsorption to clay minerals. Only Zn concentrations in estuarine sediments indicate its higher mobility and further transport. The results of this investi gation should help in understanding the ultimate environmental capacit y of the estuary and the adjacent coastal region.