Vertical distribution characteristics of organochlorine pesticides in a sediment core from Sanya Bay
三亚湾沉积柱有机氯农药的垂直分布特征

A sedimentary core from Sanya, Hainan Province was collected to explore the residues, and reactions of organochlorine pesticides (OCPs) in China over time. Pesticides were quantified by gas chromatography with electrochemical detection (GC\|ECD) with the internal standard procedure and the core was dated by 210Pb methods. The concentration range for HCHs and DDTs were 0.04~1.46 and 0.01~0.59 ng·g-1 respectively. Three peaks around the years 1965, 1971 and 1975 were found after OCPs began to be used in quantities in China in the 1960s. Sedimentary OCP concentrations decreased slightly after 1986 since the production of technical HCHs and DDTs was banned in 1983 in China. Since the 1990s, OCP concentrations showed an increasing trend with large fluctuations, which is closely related to the pattern of development in Sanya. There is some evidence of new input of lindan in recent years and enrichment of HCHs on surface sediment. The ratios of (DDD+DDE)/DDTs were lower than 0.5 in most samples and decrease from the deeper layers to the surface sediments, indicating that new input of DDTs is possible in the studied region.