Spatial distribution and mobility of trace metals in sediments of the Krka River estuary (Adriatic Sea, Croatia)

Estuarine sediments act as a sink for metal contaminants in aquatic system.As a consequence of biogeochemical processes which influence metal mobility, those sediments could become secondary source of metal contaminants for the environment.The objectives of this study were to evaluate trace metal content and mobility in sediments from the Krka River estuary.Surface sediments were sampled at 40 locations scattered through entire estuary, allowing the determination of trace metal distribution with high resolution.Mobility was assessed using two approaches: (1) pore water extraction by centrifugation and (2) diffusive gradient in thin films (DGT) sediment probes.Surface sediment analysis revealed three main pollution sources, all located in the lower part of the estuary: former ferromanganese industry, phosphate transhipment harbour and nautical marina.Mobility in the sediments is controlled by early diagenesis processes.