Distribution, enrichment and source of heavy metals in Rizhao offshore area, southeast Shandong Province.

50 surface sediments were collected from Rizhao offshore area to determine heavy metals (Cu, Pb, Zn, Cr, Cd, As, Hg) pollution. High heavy metal values were located near the two ports in the north and south study areas, which was consistent with the distribution of fine-grained sediments. According to threshold effect level (TEL) and probable effect level (PEL), Cu and As had occasionally adverse biological effects on the aquatic ecosystems. The enrichment factor (EF) values showed that most of the study area was moderate or moderately severe enrichment for As, and minor enrichment for Pb, but Hg was only moderately enriched in the river estuaries. The sources of Cu, Zn and Cr were mainly influenced by natural weathering processes via the river inputs, whereas Pb, Cd and As were mainly derived from anthropogenic sources. Hg may have both natural and anthropogenic sources.