Ecological Risk Assessment of Coastal Zones in Southern China: Spatial Variation and Content of Various Heavy Metals in Surface Sediments of China Mangroves

The spatial variation and content of nine heavy metals (Cr, Co, Ni, Cu, Zn, Mo, Cd, Pb and As) in surface sediments of six mangrove swamps in China were investigated with two habitats. The six sampling plots distributed along the southern coastline of China, covering almost all representative mangroves in mainland China. In this study, Avicennia marina as the most widely distributed mangroves in China, was selected as the research object to be representative of mangroves. Results showed that the distribution of the heavy metals in surface sediments of mangrove ecosystems greatly varied, reflecting that it is affected by various environmental factors such as organic matters and sediment grain size. The heavy metal contents in sediments decreased in the sequence of (Cr, Zn) > (Pb, Cu, Ni, Co, As) > (Cd, Mo) and the heavy metal pollution of surface sediment in China was mainly dominated by Zn, Cr, Pb, Cu. Degree of heavy metal contamination was evaluated by four methods of ecological risk assessment and the results showed that Futian mangrove swamp as representative of urban mangroves is the most polluted. Principal component analysis were also applied to examine the potential pollution sources of each heavy metal for the specific region.