Migration Mechanisms and Pump-and-Treat Remediation Simulation for Benzene and Halogenated Hydrocarbons in Groundwater at a Pesticide-Contaminated Site
Legacy contaminated sites from relocated chemical plants pose severe risks to groundwater and human health. This study investigated a pesticide-contaminated site using the Groundwater Modeling System (GMS) to construct three-dimensional geological, flow, and solute transport models, simulating migration of benzene, chloroform, and vinyl chloride and evaluating pump-and-treat remediation. Results showed initial uniform spread within 100 days, evolving to elliptical diffusion along southeast-northwest flow by 500–2000 days. Maximum migration distances reached 154.5 m (benzene), 130.5 m (chloroform), and 165.2 m (vinyl chloride), with diffusion areas of 18117.4, 13928.5, and 25043.2 m², respectively. Peak concentrations decreased over time: benzene from 53.3 to 13.0 mg/L (75.6% reduction), chloroform from 112.0 to 20.0 mg/L (82.1%), and vinyl chloride from 128.0 to 24.0 mg/L (81.3%). Dynamic pumping simulations reduced plume areas by 85.8%, 78.0%, and 85.9% at 400 days, with peak concentration reductions of 90.2%, 82.1%, and 93.8%. Within 500 days, all concentrations fell below targets, with total pumping volumes of 94500, 60000, and 72000 m³. Fenton reagent (3% dosage) effectively treated extracted groundwater. Numerical simulation optimizes contamination delineation and pumping strategies, offering a cost-efficient pathway for similar sites.