OCPs distribution and possible sources in the surface soil of Xueyu Cave
雪玉洞表土有机氯农药的分布及来源研究

Ten typical surface soil samples were taken on the top of Xueyu Cave, and 18 OCPs were analyzed by gas chromatography equipped with miro-63Ni electron capture detector. The purpose of this study was to investigate the horizontal distribution and composition of organochlorine pesticides (OCPs) in the surface soil of Xueyu Cave, and to further identify their sources. The results showed that most OCPs, except for o,p′-DDD, ε-HCH, aldrin and dieldrin, were detected in the soil samples. Moreover, 4 OCPs, including HCH, DDT, heptachlor and methoxychlor, were detected in all samples, which composed the predominant contaminations. The OCPs concentrations of surface soils ranged from 1.24 to 750.56 ng · g-1 with a mean value of 79.57 ng · g-1. The ratio of OCPs isomers implied that the unlawful using of lindane and industrial DDTs caused HCHs and DDTs pollution, and a new contamination source can be observed. Correlation analysis between 10 samples indicated that OCPs in the study area generally had the same source, and soil organic carbon was an important factor in the distribution of OCPs. Compared with the Environmental Quality Standard for Soils of China GB15618-95, the concentrations of HCHs and DDTs in these samples stayed in a low pollution level. However, due to heterogeneous distribution of the surface soil in karst region and highly developed karstification in this area, OCPs could easily transport via karst fissures or dolines into groundwater system, which posed a potential risk for dripping water and groundwater in Xueyu Cave.