某钢铁厂土壤中多环芳烃污染评价与风险评估

Evaluation and risk assessment of polycyclic aromatic hydrocarbons in soil of a steel plant

  • 摘要: 在某钢铁厂搬迁后的主厂区设置了191个采样孔,对0~5 m土壤进行分层(5层)采样,分析土壤中多环芳烃化合物(PAHs)浓度,研究了苯并(a)蒽、苯并(b)荧蒽、苯并(a)芘、二苯并(a,h)蒽、茚并(1,2,3-cd)芘5种PAHs浓度的分层变化,采用内梅罗指数(P)对土壤污染程度进行评价,并通过RBCA Version 2.5模型对土壤致癌风险进行评估。结果表明:土壤第1层、第2层和第3层的5种PAHs浓度均值高于DB11/T 811—2011《场地土壤环境风险评价筛选值》中居住用地的筛选值;除第4层苯并(b)荧蒽、苯并(a)芘、二苯并(a,h)蒽和第5层二苯并(a,h)蒽外,其他污染物的平均浓度低于居住用地的筛选值;反映土壤中PAHs污染程度的内梅罗指数自第1层向下逐渐降低,苯并(a)蒽的P从69.75降至1.99,苯并(b)荧蒽的P从84.75降至3.12,苯并(a)芘的P从163.75降至5.68,茚并(1,2,3-cd)芘的P从111.92降至0.91,二苯并(a,h)蒽的P从393.20降至3.21,表明土壤中PAHs污染程度逐渐下降;5种污染物中,苯并(a)芘的单一污染物致癌风险贡献率最高,可达56.11%,暴露途径主要为经口摄入;该厂区须经治理达到要求后方可作为居住用地。

     

    Abstract: After the relocation of a steel plant, 191 sampling holes were set in the main plant, using the layering (5 layers) sampling of 0-5 m soil, the concentration of polycyclic aromatic hydrocarbon compounds (PAHs) in soil was analyzed. The stratification of the concentration of five PAHs pollutants including benzo (a) anthracene, benzo (b) fluoranthene, benzo (a) pyrene, dibenzo (a,h) anthracene and indene (1,2,3-cd) pyrene was studied, the Nemerow index (P) used to evaluate the degree of pollution, and the RBCA Version 2.5 model applied to assess cancer risk. The results showed that the average concentration of the five pollutants in the first, second and the third layers of the soil was higher than the screening value of the residential land in the Site Soil Environmental Risk Assessment Screening Value (DB11/T 811-2011). The average concentrations of other pollutants were lower than the screening values of residential land except for benzo (b) fluoranthene, benzo (a) pyrene and dibenzo (a,h) anthracene in the fourth layer, dibenzo (a,h) anthracene in the fifth layer. The Nemerow index (P) which reflected the pollution of soil PAHs gradually decreased from the topsoil, with P of benzo(a) anthracene falling from 69.75 to 1.99, P of benzo(b) fluoranthene decreasing from 84.75 to 3.12, P of benzo(a) pyrene dropping from 163.75 to 5.68, P of indene(1,2,3-cd) pyrene decreasing from 111.92 to 0.91, P of dibenzo(a,h) anthracene decreased from 393.20 to 3.21, which indicated that the degree of soil PAHs pollution was gradually decreasing. Among the five PAH compounds, benzo(a) pyrene as single pollutant contributed the highest to carcinogenic risk, being up to 56.11%, with the main exposure pathway of oral intake. This factory area must be treated and meet administrative standard before using as residential land.

     

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