以保护地下水为目标的Ag土壤环境基准推导案例

土壤环境基准是制订土壤环境质量标准的重要依据. 借鉴国外制订保护地下水的土壤环境基准方法学,以湖南红壤、北京潮土和东北黑土为供试土壤,通过吸附试验获取重金属Ag在3种土壤中的分配系数(K_d),并通过文献调研获取3种土壤及其含水层的相关参数；采用US EPA(美国国家环境保护局)的土壤环境基准技术导则中的SSL(soil screening level)模型,并基于我国饮用水水质标准,对Ag土壤环境基准进行反推. 结果显示:Ag在红壤、黑土和潮土中的分配系数分别为7.10、56.7、132 L/kg,推导出的基于保护地下水的Ag的土壤环境基准值分别为0.440、3.04和7.80 mg/kg. 3种土壤中Ag的基准值均在发达国家或地区保护地下水的土壤环境基准值范围内,与各国基准值的差异主要是由于土壤性质、含水层类型以及Ag在土壤中的分配系数的差异所致. 

Derivation of Groundwater Protection-Based Soil Environmental Criteria for Silver:a Case Study

Soil environmental criteria are important for derivation of soil environmental quality standards, and are the cornerstone of soil environmental protection and management. However, lack of attention paid to soil environmental criteria has led to a shortage of basic data of soil in China, which seriously affects the scientific establishment of soil environmental quality standards. In the present study, foreign methods for the derivation of groundwater protection-based soil criteria were reviewed. The adsorption test was used to obtain the distribution coefficients (K_d) of silver (Ag) in Ferrosol from Hunan, Primosol from Beijing, and Isohumosol from Heilongjiang. The aquifer parameters and other key parameters of the three soil types were collected from literature. The soil criteria of silver were derived using the SSL (soil screening level) model of the U.S. EPA, based on the drinking water standard of China. The result showed that the distribution coefficients of silver in Primosol, Isohumosol and Ferrosol were 7.10,6.7 and 132 L/kg, respectively. According to the distribution coefficient and other key parameters, the soil criteria value of Ag for groundwater protection is 0.440 mg/kg for Ferrosol, 3.04 mg/kg for Isohumosol and 7.80 mg/kg for Primosol. The values are in the range of soil environmental criteria of silver of other countries or regions. The difference was mainly because of differences in soil property, aquifer types and heavy metal distribution coefficient in the soils.