Fate simulation and risk assessment of TBT and TPhT considering water level fluctuations in the TGR before and after AFS Convention implementation in China

Abstract

Background: The Three Gorges Reservoir (TGR) is the largest freshwater reservoir in China. Previous studies showed that organotin pollution is present in the TGR. In June 2011, the AFS Convention went into effect in China. In order to explore the pollution evolution processes of tributyltin (TBT) and triphenyltin (TPhT) before and after implementation of the AFS Convention and their variations with water level fluctuations in the TGR, the characteristic parameters of the TGR and the physicochemical parameters of TBT and TPhT were used to develop a level IV multimedia fugacity model considering water level fluctuations to simulate the fate, transfer, and transport of TBT and TPhT in the TGR. Based on the simulation results, exposure concentrations of TBT and TPhT were then used to assess the ecological and health risks in the TGR region (TGRR). Results: The simulation results showed that the average concentrations of both TBT and TPhT decreased in all compartments except the sediment, whereas the total content of the system continued to increase after the AFS Convention was implemented. The concentration of TBT in the sediment was higher than that in fish, while the concentration of TPhT in fish was much greater than that in the sediment. The total contents of both TBT and TPhT were highest in the sediment phase. In addition, variations in water level of the TGR significantly affected the distribution and transport of TBT and TPhT in the TGR. Conclusions: Sediment is an important source and sink of TBT and TPhT, and the water level regulation of the TGR strengthened the two roles of sediment. Both TBT and TPhT in surface water, but especially TBT, carried significant chronic exposure risks to the aquatic community of the TGR. Intake of TPhT, mainly through eating fish, posed a potential health risk to the population in the TGRR.