Migration Mechanisms and Pump-and-Treat Remediation Simulation for Benzene and Halogenated Hydrocarbons in Groundwater at a Pesticide-Contaminated Site

• • Benzene, chloroform, and vinyl chloride migration distances reached 154.5 m, 130.5 m, and 165.2 m at 2000 days, with diffusion areas of 18117.4, 13928.5, and 25043.2 m², respectively—critical for designing monitoring networks and remediation footprints. • • Peak concentrations declined by 75.6% (benzene: 53.3→13.0 mg/L), 82.1% (chloroform: 112.0→20.0 mg/L), and 81.3% (vinyl chloride: 128.0→24.0 mg/L) over 2000 days, indicating natural attenuation but insufficient for regulatory compliance without intervention. • • Dynamic pump-and-treat with staged well reduction (9–7 to 1 well) and pumping rates of 25–30 m³/d achieved plume area reductions of 85.8%, 78.0%, and 85.9% at 400 days, and concentration reductions of 90.2%, 82.1%, and 93.8%, demonstrating operational efficiency. • • Total pumping volumes for 500-day remediation were 94500 m³ (benzene), 60000 m³ (chloroform), and 72000 m³ (vinyl chloride), with 3% Fenton reagent achieving达标 treatment—quantifying cost and chemical demand for full-scale implementation.