Organotins in the aquatic media of secondary anabranches in the Three Gorges Reservoir Region, China

The Three Gorges Reservoir Region (TGRR) is one of the most sensitive areas of ecological environment in China. As vital backwater areas, the secondary anabranches of the TGRR were prone to eutrophication in Spring which would affect the distribution and transfer of organotins (OTs) among aquatic media. This study quantified the concentrations of butyltins (BTs) and phenyltins (PhTs) in water columns and aquatic media of two anabranches of the TGRR, the Daning River (DR) and the Xiaojiang River (XR) during the state of eutrophication. Our results showed that the average concentrations of BTs and PhTs in surface water are 43.91, 81.25 ng Sn L-1 in the DR, and 63.49, 69.21 ng Sn L-1 in the XR, respectively, and there were no obvious differences in the concentrations of BTs and PhTs across the water columns in the DR and XR. PhTs, especially monophenyltin (MPhT), are predominated in the dissolved phase, whereas BTs, especially dibutyltin (DBT), are predominated in both suspended particulate matter (SPM) and the sediment. Shipping and agricultural activity were likely the sources of OTs in both the DR and XR. High concentrations of tributyltin (TBT) and triphenyltin (TPhT) are still present in the aquatic media of the TGRR, and pose a significant risk to aquatic organisms due to the potential for bioaccumulation. Therefore, it is necessary to further monitor and assess OTs especially PhTs in surface water, and to continue to restrict the use of OTs to protect the aquatic environment of the TGRR. (C) 2018 Elsevier Ltd. All rights reserved.