Simulating the Transfer Flux and Fate of Organochlorine Pesticide in Beijing

This study taking Beijing as the study area, simulated the transfer and fate of Hexachlorocyclohexane(HCHs) isomers in ten environmental compartments using Level Ⅲ fugacity model. The concentrations of HCHs isomers in air, surface water, soil, sediment, vegetation leaves and roots, and fish as well as transfer fluxes across the interface between the compartments were derived under the assumption of steady state. The calculated concentrations were validated by independent data collected from the literature. There was generally good agreement between the estimated and the observed concentrations and the differences were mostly less than (0.7) log unit and approximately one order of magnitude for air and fish. The simulating results indicate that during the period when HCHs was largely applied, the main source of HCHs is agricultural application (134t/a) and air advection (623t/a) from windward, which accounting for 92% of the overall input; Among all transfer processes the air-soil deposition (80t/a), soil erosion (16t/a) and soil-air diffusion (11t/a) are the primary, accounting for 68.6%, 13.8% and 9.6% respectively; and air advection to leeward (600t/a) and degradation in soil (133t/a) are the key routes for HCHs to disappear from the study area. Around 97% of HCHs accumulated in soil, and only 0.32%, 0.52% and 1.9% in the air, water and sediment respectively. The crops and fish also contain 0.6% or so HCHs and serve as the direct route for human exposure.