滇东耕地土壤铅安全阈值研究

Safe threshold value of lead in cultivated land soil in eastern Yunnan,China

为科学划分受污染耕地的环境质量类别、精准判别污染土壤的食物链风险,基于土壤-农作物野外协同采样结果开展受污染土壤重金属的安全阈值研究,选择受地质高背景与人类活动叠加影响、耕地土壤超筛选值比例较大的滇东地区为研究区,以谷物类农产品-土壤协同采样数据为基础,同时考虑土壤理化性质,通过分析样品中铅(Pb)的生物富集因子并利用物种敏感度分布法(SSD法)和建立回归模型推导不同pH范围下的耕地安全阈值。结果表明:在pH≤6.5、6.5<pH≤7.5、pH>7.5范围下,SSD法推导的全量安全阈值分别为84.4、126.3 mg·kg^(-1)和187.4 mg·kg^(-1),推导的有效态阈值分别为20.7、52.1 mg·kg^(-1)和104.5 mg·kg^(-1);建立回归模型推导的不同pH范围(pH≤5.5、5.5<pH≤6.5、6.5<pH≤7.5、pH>7.5)下的有效态含量阈值分别为20.2、42.5、56.3 mg·kg^(-1)和94.1 mg·kg^(-1)。通过对研究区域内协同采样数据的验证和比对发现,回归模型预测Pb有效态含量阈值正确率最高(88.1%),建议将该预测值作为滇东区域农用地土壤环境质量类别动态调整的依据更为科学。

There is an urgent need to carry out research on the safety threshold of heavy metals in contaminated soil based on the results of soil-crop field co-sampling.In this study,eastern Yunnan,which is affected by the superposition of high geological background and human activities,was selected as the research area.Based on co-sampling data of the cereal agricultural products and soil,and considering the physical and chemical properties of the latter,the analysis of lead(Pb)in the samples was carried out.The bioconcentration factors of cultivated lands at different pH ranges were deduced using the species sensitivity distribution(SSD)method and by establishing a regression model of safety threshold values.According to the SSD results(pH≤6.5,6.5<pH≤7.5,pH>7.5),the full-dose safety thresholds were 84.4,126.3 mg·kg^(-1),and 187.4 mg·kg^(-1),respectively,and the effective thresholds were 20.7,52.1 mg·kg^(-1),and 104.5 mg·kg^(-1),respectively.A regression model was established to deduce the thresholds of available Pb content in soils at pH≤5.5,5.5<pH≤6.5,6.5<pH≤7.5,and pH>7.5,whereupon the values were revealed to be 20.2,42.5,56.3 mg·kg^(-1),and 94.1 mg·kg^(-1),respectively.Through verification and comparison of the co-sampling data in the study area,it was found that the regression model had the highest accuracy(88.1%)in predicting the threshold of available soil Pb content.It is suggested that the predicted value can be used as the basis for a more scientific dynamic adjustment of the categories of soil environmental quality of agricultural land in eastern Yunnan.