北京地区有机氯农药的跨界面迁移与归趋

Simulating the Transfer Flux and Fate of Organochlorine Pesticide in Beijing

以北京地区为研究区域,利用三级逸度模型方法,建立了有机氯农药在北京多介质环境中迁移、转化和归趋的稳态非平衡模型.对六六六(HCHs)各异构体的计算浓度与实测浓度进行了验证,两者残差大部分小于0.7个对数单位,仅气相和鱼相浓度接近或略超过1个对数单位.计算结果表明,在持续用药期间,HCHs的主要来源是农业施用(134t/a)和气平流输入(623t/a),约占总输入量的92%;最主要的界面迁移通量依次为:气 土沉降(80t/a,68.6%)、土 水迁移(16t/a,13.8%)和土 气扩散(11t/a,9.6%)等;而土壤中的降解(133t/a,79.7%)和气平流输出(600t/a,17.6%)则是HCHs从研究区域消失的最主要途径;土壤中HCHs储量(245t)占总储量(253t)的97%,而气、水和沉积相中仅占0.32%、0.52%和1.9%.作为人类主要食物也是最直接暴露途径的农作物和鱼体内,分别含有HCHs360kg和13kg,生物相储量占总储量的0.6%左右.

Beijing is taken as the study area, and the transfer and fate of Hexachlorocyclohexane (HCHs) isomers are simulated 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 (134 t/a) and air advection (623 t/a) from windward, which accounting for 92% of the overall input; Among all transfer processes the air-soil deposition (80 t/a), soil erosion (16 t/a) and soil-air diffusion (11 t/a) are the primary, accounting for 68.6%, 13.8% and 9.6% respectively; and air advection to leeward (600 t/a) and degradation in soil (133 t/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.