Abstract：
Given the increasing concern over Cd contamination of agricultural soils in China, reducing the availability of the toxic metal has become an important remedial strategy. However, the lack of a unified evaluation framework complicates the assessment of remediation efficiency of different practices. Here, we evaluated the general extraction method (GEM) of available Cd in nine typical soil types by comparing extraction agents, including CaCl2, EDTA, Mehlich-Ⅲ, HCl and DTPA. The safe grain concentration of different agricultural products from National Food Safety Standards Limits of Contaminants in Food (GB 2762-2022) was then applied to understand soil limited available Cd concentration based on dose-response curves. We also derived environmental risk threshold (HC5) values for Cd remediation in agricultural soils by constructing species sensitivity distribution (SSD) curves. The results showed that Mehlich-Ⅲ best predicted Cd accumulation in crops (with 76.5% of explanation of grain Cd) and was selected as the GEM of soil available Cd for subsequent analyses. The regression coefficient (R2) of dose-response curves fitting between Cd absorption in crop tissues and soil available Cd extracted by GEM based on 30 different crop species varied from 51.0% to 79.5%, and the derived limit concentration of soil available Cd based on standard GB 2762-2022 was 0.18-0.76 mg‧kg-1. An HC5 of 0.19 mg‧kg-1 was then calculated, meaning that a concentration of available Cd in agricultural soil below 0.19 mg‧kg-1 ensures that 95% of agricultural products meet the quality and safety requirements of standard GB 2762-2022. The prediction model was well verified in the field test, indicating that can correctly estimate the soil available Cd based on the content of Cd in plant. This study provides a robust scientific framework for deriving the risk threshold for Cd remediation in agricultural soils and could be quite useful for establishing soil remediation standards.
摘要：
鉴于中国农业土壤镉污染的日益关注，减少有毒金属的可用性已成为重要的补救策略。然而,缺乏统一的评估框架，使评估不同做法的补救效率变得复杂。这里,我们通过比较提取剂，评估了九种典型土壤类型中有效Cd的一般提取方法（GEM），包括CaCl2、EDTA、Mehlich-Ⅲ,HCl和DTPA。应用《食品安全国家标准食品中污染物限值》(GB2762-2022)中不同农产品的安全粮食浓度,基于剂量-响应曲线了解土壤中有效Cd浓度。我们还通过构建物种敏感性分布（SSD）曲线，得出了农业土壤中Cd修复的环境风险阈值（HC5）值。结果表明，Mehlich-Ⅲ对作物中Cd的积累预测最好（占籽粒Cd的解释量的76.5％），并被选为土壤有效Cd的GEM进行后续分析。基于30种不同作物的GEM提取的土壤有效Cd与作物组织中Cd吸收之间的剂量响应曲线拟合回归系数（R2）在51.0％至79.5％之间变化。基于GB2762-2022标准的土壤有效Cd的推导极限浓度为0.18-0.76mg·kg-1。然后计算出0.19mg·kg-1的HC5，意味着农业土壤中有效Cd的浓度低于0.19mg·kg-1，可确保95％的农产品满足GB2762-2022标准的质量和安全要求。预测模型在现场试验中得到了很好的验证,表明可以根据植物中Cd的含量正确估算土壤有效Cd。这项研究为得出农业土壤中Cd修复的风险阈值提供了一个可靠的科学框架，对于建立土壤修复标准可能非常有用。
