土壤筛选值在镉污染稻米产地环境评价与分类适用性探讨

Applicability of risk screening values for soil contamination of agricultural land in evaluation and classification of cadmium-contaminated rice producing areas

为科学地进行农用地土壤环境质量评价及环境质量类别划分,以稻田镉(Cd)污染为例,以全国典型稻米产区土壤与稻米Cd含量对应样点数据为基础,以土壤Cd与稻米Cd非对应性超限值情况即误判率为判定参数,分析土壤污染风险筛选值对稻米产地环境质量评价及类别划分的适用性。结果表明,在湖南长株潭、广东北部等区域采用筛选值评价产地环境质量存在较多误判情况。在高误判区,采用实地采样多参数分析混合线性建模的方式筛选影响稻米富集Cd的关键因子,结果表明,除土壤Cd全量及pH等因子外,土壤钙(Ca)也对稻米富集Cd有重要影响。因此在产地环境安全评价及类别划分时,对于以筛选值为依据误判率较高的区域,应加入其他土壤关键因子进一步研究,以避免误判。

Risk screening values for soil contamination of agricultural land are fundamental for the assessment and classification of soil en vironmental quality. However, owing to the complexity of the accumulation and enrichment of soil pollutants in crops, the evaluation of soil environmental quality and the classification of safety utilization categories of agricultural land based on the risk screening values for soil contamination are difficult to reflect the actual conditions in some regions. In the current study, Cd in paddy soils as a typical pollutant and the non-correspondence exceeding standard( misjudgment rate) between Cd concentrations in soils and rice samples as the decision param eter were used to investigate the applicability of the risk screening values in environmental quality assessment and classification of rice pro ducing areas based on Cd concentrations in corresponding soil and rice samples in typical rice producing areas in China. The results showed that there were errors in the evaluation of environmental quality of rice producing areas using the risk screening values for the Chang-Zhu-Tan of Hunan Province and the northern area of Guangdong Province. In the high misjudgment area, the key factors affecting the accumulation of Cd in rice samples were screened by field sampling multi-parameter analysis and mixed linear modeling. It was ob served that besides total Cd concentrations and pH values of soils, the concentration of Ca in soils had an important influence on Cd enrich ment in rice samples. In order to avoid misjudgments, future studies should focus on the areas with high misjudgment rates based on risk screening values and other critical factors of soils.