History of the accumulation of trace metals in sediments of the saline Rogoznica Lake (Croatia)

Geochemical and sedimentological characteristics, the sedimentation rate (by Cs-137 dating) and the history of the accumulation of trace metals (Cd, Pb, Cu and Zn) in sediments from anoxic, marine water of the Rogoznica Lake, Croatia, have been studied. The sediment is a fine-grained silt throughout the profile, characterized as an authigenic carbonate sediment of mainly biogenic origin, belonging to the anoxic-sulfidic sedimentation environment. The relatively high sedimentation rate (0.093 g/cm(2) per year) in the Rogoznica Lake, in comparison with the nearby coastal area, and the Krka River Estuary can be explained by higher primary biological production in the upper, oxic water layer, as well as the absence of sediment resuspension. The Rogoznica Lake behaves as a 'sediment trap' because of its small dimensions and sheltered position. The concentrations of trace metals in sediments are in the range usual for unpolluted marine carbonate sediments. Nevertheless, concentrations of Pb, Cu and Zn, in the uppercore profile of recent and sub-recent (up to the past 40 years) sediments, reflect anthropogenic influences. Leaded gasoline seems to be the principal anthropogenic source of Pb enrichment, while for Zn and Cu it may be of a communal origin, possibly due to recent tourist activity in this area.