Concentrations and distributions of 18 organochlorine pesticides listed in the Stockholm Convention in surface sediments from the Liaohe River basin, China

Organochlorine pesticides (OCPs) were analyzed in 26 surface sediment samples from the Liaohe River basin, and the distributions of and potential environmental risks posed by OCPs in the basin were evaluated. Eighteen OCPs listed in the Stockholm Convention were determined using isotope-dilution gas chromatography-high resolution mass spectrometry. This is the first study of hexachlorobenzene (HCB) in the Liaohe River basin sediments. The total OCP concentrations were 0.39-68.06ng g(-1) dry weight. The total alpha-, beta-, gamma-, and delta-hexachlorocyclohexane (HCH), the total dichlorodiphenyltrichloroethane (DDT - p,p '-dichlorodiphenyldichloroethane (DDD), p,p '-dichlorodiphenyldichloroethylene (DDE), o,p(')-DDT, and p,p '-DDT), and the HCB concentrations in the sediment samples were 0.1-28.48ng g(-1) (mean 4.01ng g(-1)), 0.08-6.52ng g(-1) (mean 3.07ng g(-1)), and 0.18-24.8ng g(-1) (mean 4.38ng g(-1)), respectively. The HCB concentrations were higher than the concentrations of the other OCPs, and the HCHs and HCB together were the dominant OCPs. beta-HCH was the most abundant HCH isomer. The concentrations of DDTs and other OCPs were relatively low, and the (DDE+DDD)/DDT ratios (>0.5) and DDD/DDE ratios (