Distribution, pollution status and controlling factors of trace metal(loid)s in Yellow River Estuary and adjacent area

This study examined the spatial distribution, contamination status and controlling factors of trace metal(loid)s of the surface and bottom water, surface sediments in the Yellow River Estuary and adjacent area. The results indicated that the distribution of metal(loid)s in the surface and bottom water is relatively consistent, and high concentrations detected in the region extending from the Yellow River Estuary to the northwest of the study area. However, the concentrations of all metal(loid)s in the water bodies are below the limits specified for Grade I seawater issued by the Ministry of Ecology and Environment of China. In the surface sediments, high-concentration areas of metal(loid)s are mainly distributed in regions with fine-grained sediments, such as the Yellow River Estuary and the northern part of the study area. The assessment results obtained by using the Geo-accumulation index and Potential ecological hazard index indicate that the pollution of Hg and Cd is serious, besides the geological background, it is significantly affected by releases from human activities. Most metal(loid)s in the water bodies of the study area come from the input of the Yellow River and the impact of near-shore human activities. Similarly, in the surface sediments, most metal(loid)s are derived from the Yellow River input, while Hg, Pb, Cd, and As may also be affected by offshore industrial activities. The spatial distribution of metal(loid)s is controlled by the enrichment of heavy metals in fine-grained sediments under hydrodynamic sorting, as well as sediment components such as TOC content.