Abstract

 The Pearl River Estuary (PRE) is created by the inflow of freshwater from the largest river system that drains into the South China Sea. In recent years, massive economic growth and industrial development in the region has led to excessive release of waste into the environment. The accumulation of contaminants in sediments is likely to pose serious environmental problems in surrounding areas. Surface and core sediment samples were collected from the PRE, and the distribution of heavy metals and persistent organochlorine pesticides were studied. The concentration ranges of BHCs and DDTs in surface sediments were in the range of 0.24 - 4.98 ng/g and 0.81 - 23.3 ng/g, respectively. There was general correlation between the concentrations of BHCs and DDTs in the surface sediments. Heavy metals (e.g. Pb, Zn, and Cu) were also enriched in the surface sediments. Comparing with historical monitoring results, the sediment metal concentrations have increased over the last 20 years, particularly Pb. Heavy metals in the enriched sections were also evaluated by a sequential extraction method for possible chemical forms. The 206Pb/207Pb ratios in the metal enriched sediment sections also revealed the influence of anthropogenic sources. The concentrations of BHCs and DDTs in surface sediments also showed close correlation with Zn and Pb, which may reflect the similar pollution sources and their associations with sediment particles during the transportation and deposition in the estuary. The spatial distribution patterns of organochlorine pesticides and heavy metals in the estuary indicated the major contaminant sources around the river mouth areas, particularly on the wastewater, sewage discharge and agricultural soil run-off points.