Spatiotemporal variation and source apportionment of organotin compounds in sediments in the Yangtze Estuary

BackgroundThe Yangtze Estuary is a vital habitat and breeding ground for many rare species (e.g., Chinese sturgeon,Chinese paddlefish). From the view of marine ecosystem health, organotin compounds (OTCs) should be of great concern in this area based on their broad applications and potential threats. At present study, five OTC species were determined in 28 and 26 surface sediments from the Yangtze Estuary (including the Nearshore area, Estuarine Turbidity Maxima (ETM) zone and Plume zone) in 2015 and 2016, respectively. Meanwhile, four sludge samples were collected from the adjacent Shidongkou Wastewater Treatment Plant to perform a source apportionment.ResultsThe sum of OTCs presented a decreasing trend towards the open sea, averaging 4.86.0ngSng(-1)dw in the Plume zone. While OTC levels in the Nearshore area (2.9-34.6ngSng(-1)dw) were similar with those in the ETM zone (5.6-36.0ngSng(-1)dw), and the sites belonging to the Deepwater Navigation Channel showed heavier contamination in the ETM zone than the Nearshore area. There are abundant suspended particles and organic matters in the ETM zone that can effectively capture the hydrophobic compounds. Besides, OTC contamination in shoreside zone was more serious than those in channel center. High OTC loads (average 633 +/- 124ngSng(-1)dw) were also found in sludge samples from adjacent wastewater treatment plant.Conclusion p id=Par3 Land-based sources (e.g. sewage discharge, runoff) are probably one of the predominant pathways of OTCs entering the ocean. Combining with previous observation in 2014, OTC contamination in the same ten sites varied slightly with years. Risk assessment indicated that the concentrations of tributyltin (TBT) are sufficient to pose ecosystem threats especially in the ETM zone. Hence, OTC contamination issuesin the Yangtze Estuary still can not be neglected.