Distribution and enrichment of heavy metal in the north of Wharton Basin, Indian Ocean.

Currently, there is no research focusing on heavy metals in deep-sea sediments from the northern part of the Walton Sea Basin in the Indian Ocean. Due to its unique geographical location, this area is ecologically significant to the Western Pacific-Indian Ocean system. Therefore, this study collected nine surface sediment samples from the Christmas Island Seamount Province using the Jiaolong human occupied vehicle (HOV) to investigate and elucidate the spatial distribution, enrichment characteristics, and ecological risks of heavy metals. By testing the concentrations of nine heavy metals (Hg, Cd, Pb, etc.), we analyzed the spatial differentiation characteristics and conducted risk assessments using the enrichment factor (EF), potential ecological risk index, and Marine Sediment Screening Benchmarks (MSSB). The results indicate that heavy metals are enriched in deep-water siliceous clay areas (>4200 m) and depleted in shallow-water calcareous oozes. Except for chromium and zinc, other metals exhibit enrichment, but mainly from natural sources (land input, volcanic activity). The overall ecological risk in the study area is relatively low, with cadmium being the main moderate risk factor and mercury posing a potential risk to the local area, both of which require continuous attention. Despite the limitations of this study due to the limited number of sampling points and scarce historical research, the results provide valuable insights into the current risks of heavy metals in the study area and serve as a baseline reference for future research in this sparsely explored region.