Integrated assessment of trace elements contamination in sediments of a typical aquaculture bay in China: Ecological toxicity, sources and spatiotemporal variation

Trace elements contamination in estuarine and bay ecosystems has become a serious problem, especially in bays with frequent aquaculture activities. To explore the pollution risk, sources and trends of pollution trace elements in Dongshan Bay, a typical aquaculture bay in China, the concentration and spatial distribution of seven trace elements in surface sediments were investigated. In this study, Zn was the element with the highest content in surface sediments, followed by Pb and Cr, while Cd was the lowest, but the average concentrations of Cd and Hg exceeded the regional background values. High levels of trace elements were distributed in estuaries and aquaculture areas, which were illustrated also by the SOM model. An evaluation of the pollution load index (PLI), geo-accumulation index (Igeo) and potential ecological risk index (PERI) demonstrated that Cd and Hg were the principal pollution elements and ecological risk factors in the surface sediments of the Bay. A positive matrix factorization model (PMF) revealed that the main sources of trace elements were natural sources, petrochemical industry and fossil fuel combination emissions, use of agricultural fertilizer, and industrial and agricultural sewage discharge. Comparative analysis found that since 2008, the mean content of Cu, Pb, Zn, and As have decreased significantly, while the content of Cd, Hg, and Cr have increased significantly. This information will help marine management efforts in taking effective measures to prevent environmental risks caused by trace elements pollution, especially related to aquaculture.