Source-to-sink process and risk assessment of heavy metals for the surface sediment in the northern South China Sea

Heavy metal input from the coastal urbanization and industrialization and their potential ecological risks have been a great concern in the northern South China Sea (NSCS). Our results showed that the surface sediments in the NSCS mainly include sand, silt, and sandy silt. CaO and Sr are fixed in the fine-grained biogenic calcareous debris. Sc, V, Cr, Co, Ni, Ba, and REE are the least contaminated and mainly of felsic crustal origin, with the supply largely from the Han and Pearl River estuaries in the Eastern and Western NSCS, respectively. Enrichment in Cu-Pb-Zn might be from both natural and anthropogenic inputs, and their contamination is generally at a low-risk level. As-Cd accumulation is mainly from anthropogenic provenance related to the aerosol precipitation. The anthropogenic As-Cd contamination resulted both from the industrial/urbanized discharge along the Guangdong Eastern Coastal and the agricultural/aquafarming activities along the Moyang River Estuary-Hainan Eastern Coastal.