Spatial variation, sources, and potential ecological risk of metals in sediment in the northern South China Sea

Heavy metals are of great concern to humans because of their persistence, bioaccumulation, and toxicity. A study on the spatial variation, sources, and potential ecological risk of heavy metals in the coastal sedimentary environment are helpful to clarify the pollution history of aquatic systems and effectively manage and control heavy metal pollution. However, most studies are limited to the Pearl River Estuary region. To investigate the spatial distribution characteristics, sources, and potential ecological risks of heavy metals (Cr, Cu, Pb, Ni, Sn, Zn, As, Cd), a total of 41 sediment samples from the northern South China Sea (NSCS) region were analyzed. The results show that Cu, Ni, Pb, and Zn have similar distribution patterns and their migration path in the coastal area is mainly controlled by the coastal current in western Guangdong. Meanwhile, these metals also have similar sources, i.e. natural weathering products. The distribution patterns of Cr, Sn, Cd, and As are not affected by the coastal current, and the sources of these metals are not only natural weathering products but also human inputs such as electroplating and electronic industries and runoff from agricultural sites. Agricultural activities, coal-burning activities, and aerosol precipitation may be another important source of human activities for As. More than half (65.9 %) of the sampling sites were categorized as having low potential ecological risk, 24.4 % for moderate risk, 7.3 % for considerable risk, and 2.4 % for high potential ecological risk, and the potential ecological risk metals of Cr, Cd, and As in NSCS should be more attention.