[Distribution Characteristics and Source Identification of Organochlorine Pesticides in the Karst Groundwater System]

Chongqing Laolongdong and Qingmuguan karst underground rivers were selected as the research objects, and 21 kinds of OCPs in those two underground rivers were analyzed by gas chromatography (GC-μECD). The results showed that, o,p'-DDE,p,p'-DDE, o,p'-DDD were not detected in Nanshan and Qingmuguan underground rivers; o,p'-DDT and dieldrin were not detected in Qingmugang; but the detection rate of the rest of the OCPs in those two underground rivers was as high as 100%. HCHs and ALDs were the most dominant compounds in Laolongdong underground river, whereas HCHs and methoxychlor were the most dominant compounds in Qingmuguan. The concentration range of total OCPs in Qingmuguan was 145-278 ng·L^-1 with a mean value of 213 ng·L^-1. The concentration range of total OCPs in Laolongdong was 17.7-40.8 ng·L^-1 with a mean value of 32.7 ng·L^-1. The OCPs component showed an increasing trend from the entrance to the exit of those two underground rivers. By analyzing the source of OCPs pollution, DDTs in the two underground river basin came from the historical industrial DDTs input; chlordane mainly came from atmospheric deposition. HCHs was the main source of Lin Dan's input, Nanshan underground river was historical pollution, whereas there was a new HCHs input from Ganjiachao in Qingmuguan upstream. Compared with the water bodies at home and abroad, the concentrations of HCHs and DDTs in Nanshan underground river water were at low level, whereas those in Qingmuguan were at medium to high level. Comparing with the hygienic standard of foreign water, it could be observed that Nanshan underground river and Qingmuguan underground river were not able to meet the standard of drinking water safety standard. For the sake of protecting the ecological environment of the underground river, land application of organic chlorine pesticide should be banned in Qingmuguan.