农用地土壤Cd有效态含量的生态安全阈值研究
Study on the safe threshold value of available Cd in agriculture land soil
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摘要: 为科学评估利用物种敏感性分布法(SSD)研究土壤有效态Cd含量安全阈值的可行性,以江西省上饶市Cd污染农田为研究对象,在统计分析区域农田土壤重金属总量、有效态含量和水稻籽粒中重金属含量的基础上,采用土壤Cd总量-有效态Cd含量线性回归方程和基于Logistic函数分布模型的SSD法,分别推导土壤中有效态Cd的安全阈值。结果表明,研究区农用地土壤存在较大范围的Pb、Cd超标现象,点位超标率分别为54.70%和68.38%,有效态Cd含量较高,平均值为0.22mg/kg;研究区有34.98%的点位存在糙米Cd含量超标,Cd是研究区农用地土壤和糙米中的主要污染物。通过线性回归方程和土壤筛选值标准,反推计算研究区农用地土壤中土壤有效态Cd含量阈值为0.149 mg/kg~0.183 mg/kg。利用Logistic函数分布模型拟合基于有效态含量的SSD曲线,保护当地95%的糙米不超标的土壤有效态Cd的安全阈值为0.160 mg/kg,验证表明基于SSD法推定重金属有效态含量安全阈值较为科学,可用于指导当地重金属污染农用地土壤的安全利用,并对其他酸性土Cd污染区具有参考意义。Abstract: To scientifically evaluate the feasibility of using the species sensitivity distribution method (SSD) for studying the safety threshold value of available Cd in agriculture land soil , the Cd-contaminated farmland in Shangrao City, Jiangxi Province was used as a research object in this study. The present study statistically analyzed the total heavy metal, heavy metal availability content, and heavy metal content in rice grains, and the linear regression equation of total soil Cd - availability content of soil Cd and the SSD method based on logistic function distribution model were used to derive the safety thresholds for the availability of Cd in soils, respectively. The results showed that there was a large range of Pb and Cd exceedances in farmland soils, with 54.70% and 68.38% exceedances at the sites, respectively. The soil Cd availability content was high, with an average value of 0.22 mg/kg, and 34.98% of the sites had brown rice Cd content exceedances, and Cd was the main contaminant in farmland soils and brown rice in this study area. The linear regression equation and soil screening value criteria were used to back-calculate the soil Cd availability content thresholds of 0.149 mg/kg to 0.183 mg/kg in agricultural soils and using a logistic function distribution model to fit an SSD curve based on the available content, the safe threshold value of soil availability Cd to protect 95% of local brown rice from exceeding the standard was 0.160 mg/kg in the study area, respectively. The results further validate that the presumed safe threshold of heavy metal availability content based on the SSD method is more scientific and can be used to guide the safe use of local heavy metal contaminated farmland soils and has reference significance for other acidic soil Cd contaminated areas.
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