Deposition history and ecological risk assessment of heavy metals in sediments from Xuwen Coral Reef Reserve, China

摘要

The deposition history, enrichment influence factors, and ecological risk assessment of heavy metals are examined on two sediment cores retrieved from the Xuwen National Coral Reef Nature Reserve, China. Pb-210(ex) and Cs-137 dating reveals that the mean sedimentation rate is about 1.5 cm a(-1) in the reserve. The concentrations of Pb, Cd, As, and Hg in sediments begin to show evident increasing trends in the 1980s. This is most likely to be caused by the anthropogenic excessive inputs originated from the large-scale development of agricultural chemical usage, coal combustion in cane sugar industry, and marine transportation after the implementation of China open policy in 1979. The annual load of heavy metals received by the reserve in recent years is estimated at about 594 tons, in which Cr and Zn are dominated and account for a proportion of 64 %. Although the ecological risk of heavy metals is assessed as low according to the sediment quality guidelines (China marine sediment quality and US NOAA screening quick reference), appropriate pollution control measures should be undertaken to prevent the occurrences of significant adverse biological effects induced by the continuous accumulations of Pb, Cd, As, and Hg in the sediments of study area.