利用CXTFIT-VZCOMML模型推导基于保护地下水的Sb的土壤环境基准

土壤环境基准是制订土壤质量标准和进行土壤质量评价的重要依据,对保护地下水起着非常重要的作用. 通过柱试验研究了Sb(锑)在北京潮土中的迁移行为,利用嵌套有CXTFIT 2.1程序的STANMOD软件对非平衡两区模型进行计算,获得Sb在潮土中迁移的阻滞因子,同时利用VZCOMML(vadose zone contaminant migration multi-layered model)模型反推保护地下水的Sb的土壤环境基准值. 结果表明:非平衡两区模型可较好地模拟Sb在潮土中的迁移过程(r2>0.97)；Sb在潮土中的迁移阻滞因子为5.82,远小于批试验得到的阻滞因子(49.3). 基于GB 5749—2006《生活饮用水卫生标准》中ρ(Sb)的标准限值(0.005 mg/L),推导出基于保护地下水的Sb的土壤环境基准值为0.64 mg/kg,该值比一些国家或地区的土壤基准或标准值(3.1～41 mg/kg)小1～2个数量级,可能是由于Sb在潮土中的阻滞因子或分配系数(K_d)较小、稀释系数较小、地下水或饮用水标准(C_gw)偏低、土壤pH不同所致. 未来应使用多种不同类型且具有代表性的土壤,以获得更准确的、适合我国实际情况的土壤环境基准值. 初步推导出Sb的土壤环境基准值(0.64 mg/kg)可为制订国家相关标准和地下水源保护区污染控制措施提供依据. 

Derivation of Soil Environmental Criteria of Antimony Based on Groundwater Protection Using the CXTFIT-VZCOMML Model

Abstract:Soil environmental criteria values are an important basis for establishing soil quality standards and making soil quality assessments, and are very useful for protecting groundwater. Column experiments were conducted to study the migration of antimony (Sb) in primosol soil from Beijing. The two-site nonequilibrium model was calculated using the CXTFIT 2.1 program with the free software STANMOD. The retardation factor (R) of Sb was obtained from the modeled results, and the soil environmental criteria value of Sb was derived using the Vadose Zone Contaminant Migration Multi-Layered model (VZCOMML). The experimental results were well-fitted with the two-site nonequilibrium model (r2 >0.97), and the fitted R value of Sb was 5.82, which was much smaller than the value (49.3) obtained from our previous batch experiments. According to the concentration of Sb (0.005 mg/L) in the Standards for Drinking Water Quality of China (GB 5749-2006), the soil environmental criteria value of Sb based on groundwater protection was derived using the VZCOMML model. The derived value was 0.64 mg/kg, which was much lower than the values (3.1-41 mg/kg) of soil criteria or soil standards in foreign countries and regions. The differences were mainly caused by the smaller R (or K_d) of Sb in soils, dilution factor (DF) and the groundwater or drinking water standards (C_gw) of Sb. Additionally, the soil pH were also different in different areas. In the future, more types of soils in China should be studied to derive the exact values of soil environmental criteria. In this study, the soil environmental criteria value of Sb (0.64 mg/kg) was obtained by using the combined CXTFIT-VZCOMML model. The research is useful for the government to establish the national standards and control the water resource protection area of groundwater.