Heavy metal distribution in sediment profiles of the Pearl River estuary, South China

The Pearl River estuary is created by the inflow of freshwater from the lar gest river system that drains into the South China Sea. In recent years, ma ssive economic growth and development in the region has led to excessive re lease of waste into the environment. The accumulation of contaminants in se diments is likely to pose serious environmental problems in surrounding are as. The study of sediment profiles can provide much information on the meta l contamination history and long term potential environmental impacts. In t his project, 21 core samples (up to 3.65 m deep) were collected in the Pear l River estuary. About 15 subsamples from each core were analysed for moist ure content, total organic matter (L.O.I.), particle size and heavy metal a nd major element concentrations. The results show that Pb and Zn contents a re elevated in the sediments at most of the sampling sites. Compared with h istorical monitoring results, the sediment metal contents have increased ov er the last 20 a, particularly for Pb. The west side of the Pearl River est uary tends to be more contaminated than the east side due to the contaminan ts inputs from the major tributaries and different sedimentation conditions . There are close associations between Fe, Co, Ni and Cu concentrations in the sediments. Zinc and Pb contents in the sediment profiles reflect a comb ination of the natural geochemical background, anthropogenic influences and the mixing effects within the estuary. The distribution of Pb in the sedim ents shows strong influences of atmospheric inputs, probably from the coal burning activities in the region. (C) 2000 Elsevier Science Ltd. All rights reserved.