基于用地规划的大型污染场地健康风险评估

以某焦化类大型污染场地苯污染土壤为例,针对S1(单一用地)、S2(多种用地)、S3(考虑建筑设计)3种暴露情景,分析不同情景下场地土壤中苯污染的暴露途径并进行健康风险评估. S1情景下的苯致癌风险为9.2×10-5. 在S2情景下,规划的5个分区中仅E区(居住用地)苯的致癌风险(4.3×10-4)高于可接受水平(1.0×10-6), 考虑到各功能区累积致癌风险,则E区高污染可导致其他4个功能区〔A区(商业用地)、B区(城市绿地)、C区(居住用地)、D区(商业用地)〕的累积致癌风险(分别为6.5×10-6、2.2×10-6、7.3×10-6、2.2×10-5)均高于可接受水平,表明单一用地会低估污染物聚集区的风险. 在S3情景下,A、B、C区土壤中苯的致癌风险(分别为1.2×10-7、2.7×10-7、2.5×10-7)均未超过可接受致癌风险水平；D区由于污染土壤被完全清除,不存在健康风险；E区开发后由剩余土壤产生的苯致癌风险为2.7×10-5,D区受E区影响产生的累积致癌风险(1.5×10-6)高于可接受水平. 进一步分析表明,场地的用地规划与建筑设计等因素将影响风险评估中关键参数(包括污染源浓度、水文地质参数、暴露参数、受体参数等)的取值,从而影响风险评估结果；此外,各功能区之间的风险影响也不容忽视. 对于大型污染场地,结合用地规划进行暴露情景分析与风险评估更为科学合理. 

Risk Assessment Based on Planning Scenarios for a Large-Scale Contaminated Site

Exposure analysis and health risk assessment based on different scenarios (unrestricted land use (S1), multiple land use (S2) and multiple land use with underground space design (S3)) were carried out for a large-scale site contaminated by benzene in Beijing. The results showed that the primary exposure pathway was indoor vapor inhalation, with carcinogenic risks significantly higher than the acceptable level (1.0×10-6) based on the three scenarios. The results from S1 indicated that the indoor vapor inhalation was at a level of 9.2×10-5. The results from S2 based on multiple land use revealed that only the carcinogenic risk of region E exceeded the acceptable level (1.0×10-6), with the calculated carcinogenic risk at 4.3×10-4. However, if the inter-regional impacts were considered, region E caused the carcinogenic risks of all the neighboring regions to be higher than the acceptable level (1.0×10-6), with exposure concentrations of benzene about 3-5 orders of magnitude higher than those of the neighboring regions. The results from S3 revealed that the carcinogenic risks of region A, B and C were 1.2×10-7, 2.7×10-7, 2.5×10-7 respectively-lower than the acceptable risk. The risks of region E (2.7×10-5) were greatly mitigated due to contaminated soil excavation. The risk of region D was eliminated due to the excavation of all the contaminated soil, however, region D may still exceed the acceptable risk due to the impact from region E if region E is not cleaned up to meet the remediation goal. The present study concluded that land use plan and building design have great impacts on the results of risk analysis due to the impacts on calculation of exposure concentration and selection of site-specific parameters and exposure parameters and exposure pathways, and inter-regional impact analysis is also important if there is a highly elevated contamination region.