基于土壤气挥发通量的污染场地三氯甲烷健康风险评估

Health Risk Assessment of Trichloromethane at Contaminated Sites Based on Soil Gas Volatilization Fluxes

我国现行技术导则在评估VOCs呼吸暴露途径健康风险时推荐Johnson-Ettinger(J&E)模型,该模型虽然简单易用,但在实际应用中存在过于保守的问题,采用双元平衡模型(dual equilibrium desorption,DED)对J&E模型进行校正后可以在一定程度上克服该问题。为准确评估实际场地中VOCs呼吸暴露风险,探索JE-DED模型在预测实际场地中VOCs呼吸暴露途径健康风险的适用性,选取苏州某污染场地面积约314 m^(2)的重污染区域开展三氯甲烷土壤气挥发通量研究进行精细化风险评估,并与基于土壤中三氯甲烷浓度采用J&E模型和JE-DED模型的计算结果进行比较。多手段风险评估结果显示,评价区域三氯甲烷呼吸暴露途径的人体致癌健康风险水平超过可接受水平1.00×10^(-6);就本场地而言,相对于基于土壤浓度风险评估,以基于实测土壤气挥发通量的风险评估结果来表征研究区域整体暴露风险水平更加稳定;研究区域土壤三氯甲烷浓度整体偏高,J&E和JE-DED模型计算的风险水平无明显差异;通过数据模拟发现,针对该场地,当三氯甲烷浓度<6 mg·kg^(-1)时,能更好地发挥JE-DED模型的优势。该场地三氯甲烷健康风险评估结果表明,基于实测土壤气挥发通量能够一定程度上避免基于土壤浓度计算带来的偶然性结果;JE-DED模型在较低浓度时,才能发挥优势。

The Johnson-Ettinger(J&E)model is recommended by the current technical guidance of China to assess the health risks of VOCs’respiratory exposure.It is easy to use but too conservative for practical applications.The problem can be overcome to some extent by adopting the dual equilibrium desorption(DED)correction of J&E model.In order to accurately evaluate the risk posed by respiratory exposure of VOCs and test the applicability of the JE-DED model in predicting this risk in a real-world scenario,a detailed risk assessment was carried out in a polluted area of about 314 m^(2) in Suzhou,China.The results using the J&E model and the JE-DED model based on the concentration of trichloromethane in soil were compared.The results are as follows:(1)Multiple risk assessments showed that the human carcinogenic health risk level from chloroform respiratory exposure in this region was higher than the acceptable level of 1.00×10^(-6).(2)Compared with the risk assessment based on soil concentration,the risk assessment based on the measured soil air volatilization flux could more stably represent the overall exposure risk for the evaluation area.(3)No significant difference existed in the risk levels calculated by the J&E and the JE-DED models when based on soil trichloromethane concentrations.Data simulation results show that the advantages of JE-DED model are more pronounced when the concentration of trichloromethane is less than 6 mg·kg^(-1) for this site.The results suggest that measuring soil air volatilization flux can avoid inaccurate results based on soil concentration calculations to a certain extent,and that the JE-DED model is advantageous at lower contaminant concentration.