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

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