Abstract:

With the rapid development of the site remediation industry in China in recent years, accurate and effective site risk assessments have become important for remediation of contaminated sites. The systematic legislative process for the risk assessment of contaminated sites was relatively late. In some provisions, the exposure scenarios are simplified into “Class I land/Class II land”, and complex mixtures of components are simplified into single identified components. Specific guidance for site characteristic assessments tailored to specific usage scenarios has not yet been provided, potentially leading to screening and assessment errors at specific sites. Based on the “screening-assessment” framework in national standard documents, a conceptual error model was constructed for the multi-tiered risk screening and assessment process of contaminated sites. For a non-residential sensitive site (youth palace) contaminated by residual petroleum hydrocarbons from a heavy oil storage tank in a city in South China, the errors between the standard screening values of petroleum hydrocarbons and site-specific risk control values were quantitatively analyzed using two assessment methods: the simplified method and the classified carbon chain method using a probability risk assessment based on a Monte Carlo simulation. The results showed that both the simplified and classified carbon chain methods provided risk control value ranges that were higher than the overall screening values for Class I land, and the risk control values obtained by the classified carbon chain method were higher than those obtained by the simplified method. The results revealed the deviations of the land-use for “youth palace” to the simplified “Class I land/Class II land”. This study identified three typical error factors at the experimental site: sensitive/insensitive land determination, complex organic compound components, and non-residential sensitive land regarded as residential land. Methods to avoid such errors in the investigation and risk assessment of contaminated sites were also discussed. This study showed that, for special sites with atypical exposure scenarios, such as youth palaces, introducing evaluation criteria with probability risk assessment methods can avoid errors caused by the application of simplified binary standards, thereby achieving relatively balanced and refined site remediation objectives.

Key words: sensitive site, probabilistic risk assessment, screening values, exposure scenarios, petroleum hydrocarbon, toxicity assessment

摘要：

随着近年来中国城市场地修复行业的迅速发展，准确而有效的场地风险评估在污染场地修复中的地位凸显。中国对污染场地风险评估工作的系统性立法过程相对较晚，在部分规定上，仍采用如将暴露场景简单二分为“第一类用地/第二类用地”，将复杂组分混合物简化为单一标示组分等简化处理，尚未给出针对具体使用场景的场地特性评估指导，可能造成部分特殊场地的筛选评估误差。基于国家标准文件中的“筛选-评估”框架，提出污染场地分级筛选评估过程的误差概念模型。对华南某市的一处重油储罐遗留石油烃污染的非居住性敏感场地（青少年宫），通过基于蒙特卡罗模拟的概率风险评估，对2种石油烃毒性评估假设方法：简化方法和分碳段方法，定量分析石油烃的标准筛选值相对场地特性风险控制值的误差情况。结果表明，简化方法和分碳段方法均给出整体高于第一类用地标准筛选值的石油烃风险控制值区间，且分碳段方法获得的风险控制值高于简化方法。研究讨论了“青少年宫”场地在现行标准“第一类用地/第二类用地”简单二分划定下存在的偏差，定量分析了3种典型误差因素（敏感/非敏感用地界定、非居住敏感用地被视为居住用地、复杂有机物组分简化处理），并探讨了场地调查和风险评估实践中规避误差的方法。研究显示，对于青少年宫等存在非典型暴露场景的特殊场地，引入结合概率风险评估方法的评估机制，可以规避使用简单二元筛选标准导致的误差，从而达成相对平衡和精细化的场地修复目标。

关键词: 敏感场地, 概率风险评估, 筛选值, 暴露场景, 石油烃, 毒性评估