[Residual Characteristics and Health Assessment Analysis of OCPs and PCBs in Karst Groundwater]

Residual levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in karst groundwater in Nanshan Laolongdong were measured using a gas chromatograph equipped with a micro-⁶³Ni electron capture detector to determine the residual characteristics including concentration, distribution, and source of OCPs and PCBs. Results revealed that the total concentration range of OCPs was 34.8-623.2 ng·L^-1, and the mean value was 215.6 ng·L^-1, among which the total concentration ranges of HCHs, DDTs, and other OCPs were 8.2-23.6, 4.5-363.7, and 22.2-235.9 ng·L^-1, respectively, and the mean values were 15.9, 104.5, and 95.3 ng·L^-1; the total concentration range of PCBs was 6.0-40.7 ng·L^-1, and the mean value was 16.8 ng·L^-1. Overall, the pollution of OCPs and PCBs was above average; the results of multiple comparisons revealed that statistically significant differences occurred in the concentration of some OCPs and PCBs. The pollution levels in the water of each sampling point in the study area were quite different; however, the seasonal distribution of OCPs and PCBs was relatively uniform. Source analyses revealed that HCHs' source was the input of lindane in the surrounding environment, DDTs recently originated from illegal use of industrial DDT, other OCPs originated from atmospheric deposition and agricultural input, and PCBs' sources included both historical remains and enterprise production processes. The results of Pearson correlation analyses revealed that some organo-halogen pollutants were homologous or had similar sources and decomposition mechanisms. According to health risk assessment model, drinking water in the study area would not cause obvious harm to human health, but children were more sensitive to pollutants than adults.