On the effectiveness of tributyltin ban part II: Temporal and spatial trends of organotin pollution in intense sediment accumulation areas and dumping sites of the Baltic Sea

Abstract

Based on the knowledge gained from our previous study, our aim is to observe the current levels of butyltin (BTs) pollution, changes during different seasons, and the factors that affect these trends in the areas of highest concern. These areas include semi-enclosed bays in the Port that were previously affected by large tributyltin (TBT) inputs, as well as the dumping sites of dredged sediment in the Baltic Sea. Compared to previous studies, there has been a significant decrease in the levels of BTs in the Klaipeda Port. However, the sediment in the semi-enclosed bays still contained BTs, ranging from less than 0.5 ng Sn g−1 dw to as high as 728.5 ng Sn g−1 dw. Some BTs were also detected in the currently exploited dumping sites of the Baltic Sea. Moreover, butyltin degradation index (BDI) revealed occasional fresh TBT input or slow degradation both in the Port and in the Sea. Some trends in butyltin concentrations were indicative of the impact of climate change in Lithuania, which are consistent with global trends. We also found that variations in BTs concentrations were closely related to dredging and cleaning activities taking place in the Klaipeda Port. Correlation, principal component, and cluster analysis revealed close relationship between TBT and its degradation products, as well as between TBT and Zn, Pb, Cu. Ship cleaning/maintenance activities were identified as the main source of pollution in the study area. Despite the gradually decreasing BTs concentration in the Klaipeda Port, the problem is not yet completely solved.