Comprehensive insights into the occurrence, distribution, risk assessment of typical pesticides and their environmental driving effects in a large drinking water reservoir

The problem of pesticide pollution in large drinking water reservoirs is becoming increasingly prominent due to agricultural production. To systematically evaluate the distribution characteristics, seasonal fluctuations, environmental behaviors, and ecological risks of pesticides in the Fengshuba Reservoir (China), we conducted a comprehensive investigation of the seasonal changes in the concentrations of 31 pesticides, including 8 organochlorine pesticides (OCPs), 16 organophosphates pesticides (OPPs), and 7 synthetic pyrethroids (SPs). The results showed the concentrations of OCPs, OPPs, and SPs in the water phase were 121.98-321.64 ng/L, 279.28-371.75 ng/L, and 118.96-186.65 ng/L, respectively. The concentrations in the porewater phase were 3363.34-7105.00 ng/L, 8648.98-14,265.95 ng/L, and 2740.83-7738.28 ng/L, respectively. The concentrations in the sediment phase were 47.92-88.28 & mu;g/kg, 159.87-446.64 & mu;g/kg, and 29.43-99.62 & mu;g/kg, respectively. The concentrations in the soil phase were 23.62-50.76 & mu;g/kg, 96.85-184.19 & mu;g/kg, and 21.02-37.02 & mu;g/kg, respectively. Seasonal hydrology, hydraulic retention time, precipitation, temperature, and biological metabolism all impacted the concentration and composition of pesticides, but no apparent environmental gradient effect was found within the reservoir. Redundancy analysis indicated that NO3- , Dissolved oxygen (DO), Dissolved organic carbon (DOC), Organic nitrogen (ON), and Inorganic carbon (IC) were the main environmental parameters affecting pesticide concentrations. The pseudo-partitioning values in water and porewater ranged from 1.2 to 3.3 x 104 and 22.0-61.7 L/kg, respectively. The ecological risk was low for OCPs, moderate for OPPs, and high for SPs in the water phase. SPs should be considered a priority indicator for risk assessment. Future conservation efforts for reservoir system should focus on pollution prevention in the soil phase.