Spatiotemporal distribution and risk assessment of organophosphorus pesticides in surface water and groundwater on the North China Plain, China

90 groundwater samples and 14 surface water samples were collected in wet season (summer) and dry season (winter) in the North China Plain (NCP), and analyzed for 11 organophosphorus pesticides (OPPs). The results showed that the main types of OPPs in surface water and groundwater were dimethoate, dichlorvos, methyl-parathion, malathion in both summer and winter. The OPP concentrations in groundwater and surface water were higher in summer than in winter. In the vertical direction, the distribution characteristics of different four types of groundwater sampling points are different. In the horizontal direction: farmland adjacent to a river (FAR) > central farmland (CF) > nonfarm area adjacent to a river (NFAR) > central nonfarm area (CNF). The OPPs concentrations in surface water adjacent to farmland were higher than that in surface water adjacent to nonfarm area. The main factors influencing the distribution of OPPs in the groundwater and surface water were the interaction process between them, the groundwater flow field and the OPPs used in agricultural activities. The ecological risk of OPPs to surface water was greater in summer than in winter. Water Flea was at medium risk, and malathion had the greatest influence on Water Flea in both summer and winter. The non-carcinogenic and carcinogenic risks of the four main OPPs in surface water were higher than in groundwater, and were higher in summer than in winter, but they would not lead to adverse health effects on local residents.