Historical trends and pollution assessment of heavy metals in core sediments from the Jiangsu offshore area, China

To assess the historical changes and pollution status of heavy metals, core sediments from the Jiangsu offshore area of China were systematically sampled and analyzed to determine the concentrations of Cu, Pb, Zn, Cr, Cd, As, Hg, Li, Ni, and Co. The stratigraphic framework of the SYS-1501 core was identified based on sedimentary structures, sedimentary facies, grain size, and comparison with seismic reflections and other well-studied cores from adjacent areas. The Pearson’s correlation coefficient, enrichment factor (EF), geoaccumulation index (Igeo), and principal component analysis (PCA) were used to distinguish the sources and assess the pollution risk of heavy metals. The results showed no elemental enrichment or contamination in the core sediments, and the high EF and Igeo values of Pb, As, Hg, and Li may be related to the selected background values of these metals. Except for Mn, all other metals and TOC exhibited similar vertical distribution patterns that were closely related to the mean grain size (Mz). Almost all the heavy metals were positively correlated with Al, Fe, and Mz, and all had high loadings on PC1, indicating that they are naturally sourced. Manganese (Mn) had a high loading on PC2, mainly representing the effect of marine authigenic elements on the sediments. Historical changes in the heavy metals in the core sediments were predominantly related to the sedimentary environment, sediment sources, and Mz.