Spatial distribution of heavy metals in the surface sediments of Changdao Island and their sources and pollution assessment

A survey was conducted in July-August 2020 to evaluate the risk of heavy metals in the northern waters of Changdao, surface sediments from 101 sites were sampled, the types and particle size distributions of the surface sediments were studied, and the content, distribution characteristics, and correlations of 8 types of heavy metal elements were explored, including AS, PB, HG, CR, CD, CU, Zn, and Ni. The potential ecological risk index method, sediment environmental quality assessment, and geoaccumulation index method were used. Results show that heavy metal elements were mainly enriched in the waters of the southern part of Daqin Island, the northern part of Beihuangcheng Island, and the northern part of Xiaoqin Island. Most heavy metal elements were significantly positively correlated with the average particle size; sediment types were affected by tidal currents and topography. The results of risk assessment show that the study area was in a very low risk environment as a whole, and the potential ecological risk index method reflects that Cd and Hg in only some stations were at medium ecological risk; the sediment environmental quality assessment reflects that Cr, Cu and Zn were not in the natural background environment only in some sites; the geoaccumulation index method reflects that only some Cd sites were in a slightly polluted environment. The source analysis shows that the concentrations of Cd, Hg, Cu, Zn, Hg, Ni, and Cr were affected by human activities such as aquaculture and sewage discharge, while that of As was only affected by natural soils in nearby islands and nearshores.