Occurrence and possible sources of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) along the Chao River, China

•DDTs, HCHs, HCB are the dominant OCPs and PCB-118 is the major PCB.•OCP level is higher in corn fields and orchards and lower in forests and grasslands.•OCPs in soil came from new use of lindane and old application of DDTs, HCB, etc.•PCBs primarily come from atmospheric deposition.•Proper management of lindane, DDTs, HCB is critical for the water resource quality. To analyze the possible influence of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) on Miyun Reservoir, 14 soil samples and 1 water sample were collected along the Chao River, which is the main upstream source of the reservoir. A total of 24 kinds of OCPs and 12 kinds of dioxin-like PCBs were measured. Results showed that the ∑OCPs concentration ranged from 0.8145 to 16.8524ngg−1, and the ∑PCBs ranged from 0.0039 to 0.0365ngg−1. Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were the three dominant kinds of OCPs in this region, and the majority component of the PCBs was PCB-118 in both water and soil samples. The OCP ratios suggest that new inputs of lindane exist. DDTs mainly come from old technical inputs. HCHs might come from a new application of lindane, which highlights the importance of prohibited pesticide control. OCP concentrations were higher in corn fields and orchards and lower in forest lands and grasslands, which indicated that OCPs were very much influenced by human activities. The proportion of PCB components in this study area suggested that they mainly came from atmospheric deposition.