Heavy metal contamination in surface sediments of intertidal zone in central Jiangsu Province: distribution, source, and assessment

Surface sediment samples were collected at 89 stations from intertidal zone in central Jiangsu Province in 2015. The concentrations, spatial distribution patterns, and interrelations of seven heavy metals (Cu, Pb, Zn, Cr, Cd and Hg) were studied and compared with previous investigations. The pollution status was evaluated systematically with China’s national sediment quality guidelines, geoaccumulation index, and enrichment factor. Results show that the concentrations of heavy metals in surface sediment varies greatly, and the average concentration followed the descending order of: Cr＞Zn＞Cu＞Pb＞As＞Cd＞Hg. The spatial distribution was uneven. High-value areas were spot-like or in patch. The heavy metal concentrations at all stations were below the possible effect level, and the overall potential ecological risk was low. The Pearson correlation coefficients, geoaccumulation indexes, enrichment factors, and R-type factor analysis show that heavy metals Cu, Pb and Zn were not polluted or enriched, and they were mainly from crustal materials or natural weathering. Cr was slightly polluted and enriched, which were jointly affected by natural weathering and human activities. Cd, As, and Hg were enriched and heavily polluted, which were mainly derived from anthropogenic sources.