基于转移方程的蔬菜镉累积预测和土壤风险阈值推导

Prediction of Cd in vegetables and soil Cd threshold derivation based on transfer function

重金属镉(Cd)在土壤-蔬菜系统中转移方程的建立是农田Cd污染控制和风险评估的关键.本研究通过调查湖南省攸县745个土壤-蔬菜样品Cd含量,应用转移方程、敏感性分布曲线(SSD)和多元回归方法分析不同类别蔬菜Cd累积特征和影响因素,预测不同土壤条件下蔬菜Cd含量并推导相应土壤Cd风险阈值.结果表明:叶菜对Cd胁迫较根菜敏感;土壤pH、土壤总Cd和土壤有机质(SOM)是影响蔬菜Cd富集的3个主要因子;转移方程对叶菜和根菜的解释程度分别为54.2%和69.1%.土壤Cd风险阈值随土壤pH和SOM的增加而增加,根菜在严重酸化土壤区Cd累积风险较高.当前国家土壤环境质量标准对于严重酸化、有机质含量较低的土壤过于宽泛.

The construction of transfer function of cadmium （Cd） in the soil-vegetable system is important for risk management. This study investigated the Cd concentration in 745 paired soils and vegetable samples, aiming to determine the influences of major soil properties on uptake of Cd by vegetables, and to derive the soil Cd threshold for vegetable cultivation based on China foodstuff regulations. Results of species sensitivity distribution model showed that the Cd accumulation poten- tial of leafy vegetables was greater than that of rootstalk vegetables. Stepwise multiple regression analysis showed soil total Cd, pH, and soil organic matter （SOM） were major factors contributing to Cd accumulation in vegetables. The derived transfer function explained 54.2% and 69.1% of the variance for the accumulation of Cd in leafy and rootstalk vegetables, respectively. The derived soil threshold increased with soil pH and SOM contents. The rootstalk vegetables were potentially hazardous when grown in strong acidic areas. For soils in the southern China with excessive acidic nature and low SOM contents, the soil Cd limits for vegetables cultivation might be over-estimated.