活化剂联合柳树对重金属Cd污染土壤的修复效果研究

Remediation Effects of Activating Agents Combined with Willow on the Heavy Metal Cd Contaminated Soil

为有效提高植物提取污染土壤重金属的效率,以绿色安全的有机物料为活化剂代替存在安全隐患、不可降解的螯合剂及表面活性剂,探究不同活化剂对土壤重金属镉的活化效果及对植物镉积累的影响。通过室内培养试验与盆栽试验的方法,研究了紫云英、黄腐酸钾和柠檬酸3种活化剂在0.3%施用量下对污染土壤中镉的生物有效性、赋存形态的影响及活化剂强化柳树对镉的积累。结果表明:(1)添加活化剂会改变土壤的pH。培养结束时,黄腐酸钾处理对土壤pH的降低效果优于紫云英处理,显著低于对照0.50个单位(p<0.05),而酸性较强柠檬酸处理的土壤pH显著高于对照0.26个单位(p<0.05);添加活化剂均可提高土壤有机质含量。培养结束时,黄腐酸钾处理对土壤有机质含量提升效果优于其他2种活化剂,显著高于对照2.97 g/kg(p<0.05)。(2)添加活化剂均可提高土壤有效态镉含量,但不同活化剂的活化效果不同。培养20天时,紫云英与黄腐酸钾处理的土壤有效Cd含量均达到最高,优于柠檬酸处理,分别高于对照0.38 mg/kg(p<0.05),0.17 mg/kg。培养10~30天时,柠檬酸处理的土壤有效Cd含量逐渐增加,至30天时,柠檬酸处理对土壤有效Cd含量提升效果优于其他活化剂,显著高于对照处理0.39 mg/kg(p<0.05)。(3)添加活化剂影响了土壤镉形态分布,培养10~30天,3种活化剂可活化土壤残渣态Cd,提高酸可提取态Cd所占百分比。(4)3种活化剂处理对柳树的株高、生物量无显著影响,但均提高了根系的形态参数,其中柠檬酸处理的根系长度、表面积、根系体积均显著高于对照,分别提高了75.54%,80.05%,82.93%(p<0.05)。活化剂中黄腐酸钾处理明显提高了柳树叶片、枝条、根系镉含量,分别高于对照133.44%(p<0.05),75.21%,264.64%(p<0.05),并大大提高了柳树对土壤镉的富集与净化。以有机物料为活化剂,可有效提高土壤重金属生物有效性,提高植物对土壤镉的吸收,具有良好的应用前景。

To effectively improve the efficiency of plant extracting heavy metals from polluted soils, green safe organic materials were used as activating agents to replace safety hazards, non-degradable chelating agents and surfactants. The activation effects of different activating agents on soil heavy metal Cd and their effects on plant Cd accumulation were explored. The effects of three kinds of activating agents of milk vetch(MV), potassium humate(KH) and citric acid(CA) on the bioavailability and morphological characteristics of Cd in Cd-contaminated farmland soil and the accumulation of Cd by activator-fortified willay were studied by incubation and pot expriments with 0.3% application rate. The results showed that:(1) Adding an activator changed soil pH value. At the end of the culture, the effect of KH treatment on soil pH was better than that of MV, which was significantly lower than the control by 0.50 units(p < 0.05), while the pH of the soil treated with CA was significantly higher than that of the control by 0.26 unit(p < 0.05);Adding an activator could increase the soil organic matter content. At the end of the culture, the effect of KH treatment on the soil organic matter content was better than the other two activating agents, which was significantly higher than the control by 2.97 g/kg(p < 0.05).(2) Adding activator could increase the effective Cd content of soil, but the activation effect of different activating agents was different. On the 20 th day after culture, the effective Cd content of the soil treated with MV and KH reached the highest, which was better than that of CA treatment, which was higher than the control by 0.38 mg/kg(p < 0.05) and 0.17 mg/kg respectively. When cultured for 10 ~ 30 days, the effective Cd content of CA treated soil increased gradually. After 30 days, the effect of CA treatment on soil effective Cd content was better than the other two activating agents, which was significantly higher than the control treatment by 0.39 mg/kg(p < 0.05).(3) Adding activating agents changed the Cd form of soil. Cultured for 10 ~ 30 days, all three activating agents could activate soil residue Cd and increase the percentage of acid extractable Cd.(4) The three activating agents treatments had no significant effect on the plant height and biomass of the willow, but all increased the morphological parameters of the roots. The root length, surface area and root volume of CA treatment were significantly higher than the control, which increased by 75.54%, 80.05% and 82.93%(p < 0.05) respectively. KH treatment significantly increased the Cd content in the leaves, branches and roots of the willow, which was higher than the control by 133.44%(p<0.05), 75.21% and 264.64%(p<0.05) respectively, and greatly improved enrichment and purification of Cd in soil by willow. The use of organic materials as activating agents could effectively improve the bioavailability of heavy metals in soils, and should have a good application prospect in combination with plant extraction of heavy metals.