Distribution characteristics of organochlorinated pesticides in soils of karst caves in Guilin, Guangxi, China

A pioneering investigation was performed on organochlorinated pesticide (OCP) pollution of softs in karst caves in the Guilin karst area,southern Guangxi.The results show that the cave softs have been slightly polluted by OCP,with the contribution of atmospheric transport to OCP predominating.Among 17 kinds of OCP,DDT,HCH and chlordane play a dominant role in the pol- lution.The total concentration of OCP in the interior of the cave ranges from 1.19 to 11.18 ng/g,being far lower than that (range 11.41-23.62 ng/g) outside the cave.The content of HCH in softs in the cave is higher than that of DDT.Among four isomers of HCH,theβ-HCH percentage in HCH is far higher than those of the other three isomers.Exceptβ-HCH,the other three isomers are distributed evenly,which is possibly due to such factors as the stability of the cave environment and climatic zoning.In soils outside the cave,the isomer percentage and tracing indicator ratio might provide critical information on the possible recent introduction of lindane and discofol-type.The main sources of DDT and HCH in the study area are thought to be residue of organochlorinated pes- ticides used in the past.