基于J&E/AAM模型的污染场地VOCs风险防控

土壤或地下水中挥发性有机污染物经包气带迁移后进入建筑物，导致室内污染物聚集危害人体健康.为研究场地蒸气入侵的过程及影响因素，以苯为例，借助一维J&E解析模型和二维近似解析AAM模型，探究土壤性质参数对污染场地建筑物底板处蒸气衰减系数和室内蒸气衰减系数的影响，并分析两个模型的适用条件.结果表明，室内蒸气浓度（C_in）取决于建筑物底板处蒸气浓度（C_ck）和土壤气体进入室内的速率（Q_ck）.J&E模型中，室内蒸气衰减系数（α_sin）随着地基埋深增加先减后增，而AAM模型中室内蒸气衰减系数一直呈上升趋势.毛细管的存在使蒸气衰减系数降低1~2个数量级，土壤水分也可有效阻挡蒸气向上扩散.在低渗透土壤条件下，两个模型计算的室内蒸气衰减系数均在10-4左右；在高渗透土壤条件下，建筑物底板处对流作用强烈，J&E模型建筑物底板处蒸气浓度减小，室内蒸气衰减系数在10-3左右，AAM模型建筑物底板处蒸气浓度为定值，室内蒸气衰减系数随土壤渗透系数的变化大致呈线性增长，且比J&E模型结果高1~2个数量级.研究显示，当污染场地建筑物底部对流作用强烈或在砂土、壤土类土壤中，采用J&E模型更为合理；对流较弱或在粉土、黏土中，可以采用AAM模型代替J&E模型，简化计算过程，便于进行场地风险评估.污染物蒸气在砂土中穿透力较强，而黏土层可以有效阻挡蒸气的迁移，在实际场地风险管控中，可以采用换土或表层覆盖黏土的方法阻挡蒸气的迁移. 

Risk Control of VOCs Contaminated Sites based on J&E/AAM Model

The volatile organic contaminations in soil or groundwater emanate into the buildings after migration from vadose zone will lead to the indoor pollutants accumulation and endanger human health. The process of vapor intrusion was studied by developing one-dimensional J&E analytical model and two-dimensional approximate analytic AAM model. The influence of the soil property parameters on the source-to-subslab vapor attenuation coefficient and the source-to-indoor vapor attenuation coefficient of the two models were studied, while the applicable conditions of each model were analyzed. The results suggest that the indoor vapor concentration depends on the subslab vapor concentration and the vapor flow rate into the building. For the J&E model, the source-to-indoor vapor attenuation coefficient shows an increase to decrease relation with the foundation depth, however, it keeps on the rise with the foundation burial depth for the AAM model. The presence of capillary fringe can deeply reduce the vapor attenuation coefficient by 1-2 orders of magnitude, and the soil moisture can also effectively block the upward diffusion of contaminated vapor. For the case with low permeability soil, the indoor vapor attenuation coefficient calculated by the J&E model and the AAM model are around 10^-4. However, the convection effect between the subslab of building and ground surface in the permeability soil is strong, resulting in the greatly decrease of the subslab concentration and the source-to-indoor vapor attenuation coefficient to about 10^-3 for the J&E model. The subslab concentration is fixed in the AAM model, so that the attenuation coefficient of source-to-indoor vapor increases basically linearly with the soil permeability, and is 1-2 orders of magnitude higher than the J&E model. This study indicates that when the soil of contaminated site is sand or loam, or the subslab of the building has strong convection effect, the J&E model is more reasonable to evaluate the process of vapor intrusion, while the convection is weak or in silt-clay soil, the results of the two models are similar so the J&E model can be replaced by AAM model to simplify the calculation process of vapor intrusion and facilitate the risk assessment of contaminated site. The penetration of pollutants vapor in sand is strong, and the clay can effectively block the migration of vapor. In the filed risk management, the replacement sand with clay or surface covering with clay can be utilized to prevent the intrusion of contaminated vapor.