生物降解对土壤气中苯衰减系数及筛选值的影响  

Impact of Biodegradation on Attenuation Factor and Screening Level of Benzene in Soil Vapor

作　　者：钟茂生[1,2,3] 姜林[1,2,3] 姚珏君[1,2,3] 夏天翔[1,2,3] 贾晓洋[1,2,3] 彭超[1,2,3] 

机构地区：[1]北京市环境保护科学研究院,北京100037 [2]国家城市环境污染控制工程技术研究中心,北京100037 [3]污染场地风险模拟与修复北京市重点实验室,北京100037

出　　处：《环境科学研究》2014年第2期178-185,共8页Research of Environmental Sciences

基　　金：北京市科学技术委员会重大项目(D08040000360000);中意污染场地管理国际合作项目

摘　　要：以砂质土壤为例,采用Bio-vapor软件计算了生物降解对苯的ai-s（衰减系数）及筛选值的影响,并对关键影响参数〔cs（污染源苯质量浓度）、LT（建筑底板与污染源距离）、La（好氧土层厚度）和kw（生物降解系数）〕进行分析. 结果表明：当cs≥5×105mgm3时,生物降解对ai-s基本无贡献；当cs≤1×104 mgm3时,生物降解可导致ai-s降低1-2个数量级,但降幅随cs和LT的变化不明显；当cs介于二者之间时,生物降解对ai-s的作用受LT变化的影响较明显,LT升高1个数量级时,生物降解可导致ai-s降低2个数量级. 生物降解对ai-s的作用受La影响比较明显,La由0.50m增至1.50m时,生物降解可导致ai-s降低2个数量级. Bio-vapor软件预测的砂质土壤条件下La的最大值为0.63m,低于现场普遍测试结果（1.50m）,表明该模型预测结果可能过于保守,实际项目中可通过测试土壤气中各组分的纵向分布确定La. 当cs≤5×104 mg/m3时,kw由0.033h^-1增至2.000h^-1,生物降解将导致ai-s降低2个数量级. 因此,同一概念模型下考虑生物降解时土壤气中苯筛选值高于不考虑生物降解时1-2个数量级.Effects of biodegradation on the attenuation factor （ai-s） and screening level of benzene in the soil vapor were studied by using the one dimensional model, Bio-vapor for sandy soil, in particular on critical influential factors of biodegradation were simulated and discussed, including source intensity （cs）, vertical separation distance between building foundation and source （LT）, depth of aerobic zone in soil （La）, biodegradation rate （kw）. The results indicated that contribution from biodegradation of benzene to ai-s was negligible, when cs was higher than 5×105 mgm3. When cs was less than 1×10^4 mgm^3, ai-s was 1-2orders of magnitude reduction when the aerobic biodegradation process was included compared to the non-biodegradation case, but the reduction is insensitive to the change of cs and LT. When cs falls in between, ai-s decreases by 2orders of magnitude as LT increases by 1order of magnitude, and LT is a sensitive parameter. La is a critical factor in determining the biodegradation effect, and bio-attenuation decreases by 2orders of magnitude as La just increases from 0.50to 1.50m. Compared with the field measured results for La, which were always deeper than 1.50m, the modeled results for the sandy soil was 0.63m, indicating that Bio-vapor is conservative in predicting the depth of aerobic zone. Therefore determination of La through measuring the soil vapor profile in practical project is recommended. Bioattenuation was more sensitive to kw for light contaminated sites, and ai-s decreases by 2orders of magnitude as kw increases from 0.033to 2.000h-1 when cs is no more than 5×104 mgm3. The vapor screening value for benzene is 1-2orders of magnitude lower when biodegradation is considered for the same conceptual model scenario with no biodegradation.

关 键 词：生物降解 Bio—vapor模型 苯蒸气 衰减系数 筛选值 

分 类 号：X703.1[环境科学与工程—环境工程]