PRA在焦化厂污染土壤健康风险评价中的应用

Research on Application of PRA in Health Risk Assessment of Soil in a Coking Plant Site

以北京市某炼焦化学厂场地污染调查为依据,采用PRA(概率风险评价)研究了15个人体暴露参数和土壤中污染物浓度不确定性对苯、苯并[a]芘健康风险评价结果的影响.结果表明:对于表层和深层土壤,苯、苯并[a]芘各暴露途径及总暴露途径PRA95%分位值均小于相应DRA(确定性风险评价)风险值;该场地整个土层中苯的PRA总风险值为1.5×10-8～6.9×10-3,苯并[a]芘为2.3×10-9～2.2×10-3,二者95%分位值分别为3.8×10-4和1.1×10-4;苯、苯并[a]芘的DRA总风险值分别为PRA96.8%和99.1%分位值,并且二者的DRA总风险值/PRA95%分位值分别为1.5和3.2,表明DRA风险值偏保守.参数敏感性分析表明,对苯总风险不确定性贡献较大的为深层土壤中的苯浓度(贡献率为94.63%,下同)和成人暴露周期(4.12%),苯并[a]芘为表层土壤中苯并[a]芘浓度(92.63%)、成人暴露周期(2.40%)、儿童每日土壤摄入量(2.12%)和儿童暴露周期(1.21%).

Based on the previous results of contamination survey on a coking plant in Beijing, the effects of uncertainty of 15 exposure parameters and soil pollutant concentrations on human health risk assessment of benzene and benzo[ a] pyrene were investigated with the methods of probabilistic risk assessment （PRA）. Results showed that the risk values of PRA, which was located at the 95th centile in the probabilistic range of risk values, were lower than that of deterministic risk assessment （DRA） of benzene and benzo [ a] pyrene in both surface and subsurface soil through single and total exposure pathways. The total risk calculated by PRA ranged from 1.5 x 10 -8 to 6.9 x 10-3 for benzene and 2.3 x10-9 to 2. 2 x 10-3 for benzo[a]pyrene, and the values were located at the 95th centile in the probabilistic range of risk were 3.8 x10-4 and 1.1x10 -4, respectively. The total risks conducted by DRA were located at the 96.8th and 99. 1＇h centiles in the probabilistic range of risk, which were 1.5 and 3.2 times of the values by PRA. This indicated that the methods of DRA overestimated the real risk. The results of parameter sensitivity analysis revealed that the concentration of benzene in the subsurface soil （94.63%） and the adult exposure duration （4. 12% ） contributed the most to the uncertainty in benzene risk assessment, and the concentration of benzo[a]pyrene in the surface soil （92.3%）, adult exposure duration （2.40%）, soil ingestion rate （2.12%） and child exposure duration （1.21%） contributed the most to the uncertainty in benzo[ a] pyrene risk assessment.