DGT和化学提取法评价贵州赫章土法炼锌区污染土壤中镉的植物吸收有效性

Evaluation of cadmium phytoavailability in soils from a zinc smelting area in Hezhang County, Guizhou Province, using diffusive gradients in thin films and conventional chemical extractions

以马铃薯、白菜和玉米为典型作物,以贵州省赫章县"土法炼锌"冶炼区重金属复合污染土壤为供试土壤,通过盆栽试验比较了五种传统化学提取剂(HNO_3、DTPA、LMWOAs、HCl和CaCl_2)和梯度扩散薄膜技术(diffusive gradients in thin films,DGT)对土壤Cd的植物吸收有效性影响。研究结果表明:"土法炼锌"影响区土壤总体呈碱性;马铃薯与白菜可食部位对供试土壤Cd的富集系数基本相同,而玉米籽粒对供试土壤Cd的富集系数远小于块茎类和叶菜类,马铃薯、白菜和玉米的富集系数平均值分别为0.105 3、0.105 8和0.007 9;一元线性与二元回归表明DGT测定土壤有效Cd含量与作物可食部分Cd含量相关系数大于五种传统化学提取剂;五种提取态中,CaCl_2提取态测定有效态Cd也可较好预测马铃薯和白菜可食部分Cd含量(R2adj分别为0.805和0.808),HNO_3提取态测定有效态Cd也可较好预测三种作物可食部分Cd含量(R_(adj)~2分别为0.822、0.874和0.764)。在本实验条件下,DGT技术评价"土法炼锌"冶炼区土壤镉植物吸收有效性效果优于五种化学提取态,但考虑不同作物类型,土壤pH因素以及操作的简单快捷性,CaCl_2提取态和HNO_3提取态也可成为预测重金属冶炼区复合污染碱性土壤Cd的植物吸收有效性的方法。

This study aimed to investigate Cd phytoavailability by comparing diffusive gradients in thin films（DGT）with five conventional chemical extractants（HNO_3, DTPA, LMWOAs, HCl, and CaCl_2）. Twenty types of calcareous soil contaminated by mining were collected from Guizhou Province, and three tropical crops（potato, cabbage, and maize）were selected for a pot experiment. The results show that（1）the soils had been polluted by zinc smelting;（2）the bioconcentration factors of potato and cabbage were very similar and that of maize was considerably lower than those of potato and cabbage, with average values for potato, cabbage, and maize of 0.105 3, 0.105 8, and 0.007 9,respectively;（3）simple and multiple linear regression analysis shows that concentrations determined by DGT were more highly correlated with the Cd concentrations in the edible parts of the three crops than were the concentrations in the five chemical extracts, and were unaffected by soil physical and chemical properties;（4）CaCl_2-extractable concentrations showed a good relationship with the Cd concentrations in the edible parts of potato and cabbage, and HNO_3 extraction also showed a significant relationship with the Cd concentrations in the edible parts of the three crops. The present study verifies that the DGT technique may be superior to conventional extraction methods for evaluating Cd phytoavailability in field-contaminated calcareous soils, but CaCl_2 and HNO_3 extractions can be selected for assessing phytoavailability when taking into account the crop species, pollution level, cost, and the simplicity of the extractions.