直流电场与添加剂强化东南景天修复镉污染土壤

通过盆栽试验,研究交换直流电场(电压梯度1.0 V cm-1、通电时间6 h d-1)和添加剂(15 g kg-1猪粪堆肥、10 g kg-1腐殖酸肥或5 mmol kg-1乙二胺四乙酸二钠(EDTA)对超积累植物——东南景天修复镉污染土壤的影响。结果表明,施加直流电场和添加剂均显著(p0.05)提高土壤有效态镉含量,促进东南景天对镉的吸收转运。在电场作用下,东南景天地上部镉含量提高26.6%~47.5%;在添加剂(猪粪堆肥、腐殖酸肥、EDTA)作用下,东南景天地上部镉含量分别提高22.9%~33.1%、14.3%~29.4%和6.1%~12.0%。双向切换电场方向能有效控制土壤pH的剧烈变化,施加直流电场对东南景天地上部生物量无显著影响。施加15 g kg-1猪粪堆肥和10 g kg-1腐殖酸肥显著提高东南景天地上部生物量,增幅分别为40.3%~43.7%和16.3%~18.2%,但是,添加5 mmol kg-1EDTA却显著抑制东南景天的生长,东南景天地上部生物量减少7.3%~7.5%。综合东南景天地上部镉含量和生物量,在猪粪堆肥―交换直流电场和腐殖酸肥―交换直流电场的联合作用下,东南景天地上部镉积累量分别提高了135%和100%,因此,猪粪堆肥和腐殖酸肥联合交换直流电场可显著促进东南景天对镉的吸收积累,提高东南景天修复镉污染土壤的效率。

Intensification of Phytoremediation of Cd Contaminated Soil with Direct Current Field and Soil Amendments in Addition to Hyperaccumulator Sedum Alfredii

Objective] A pot experiment had been carried out to investigate effects of soil amendments (pig manure compost,humic acid,EDTA) and a switched polarity DC electrical field on phytoremediation of Cd contaminated soil with hyperaccumulator Sedum alfredii.Method] In this experiment,plants of Sedum alfredii,a species of hyperaccumulator,were planted into pots containing loamy soil pretreated with 15 g kg-1 of pig manure compost,10 g kg-1 of humic acid,or 5 mmol kg-1 of EDTA,separately,as treatments and with nothing as control.In addition,the pots were subjected to another treatment:novoltage (without electrical field) or direct current (DC) electrical field (1 V cm-1 with switching polarity every day).At the end of the experiment,dry weights of shoots and roots of the plants,cadmium (Cd) concentration in the plants and soil available Cd (diethylene triamine pentaacetic acid (DTPA) extractable) were determined.Result] Available (DTPA extracted) Cd in the soil increased significantly in the treatments subjected to DC electrical field and amended with pig manure compost,humic acid,or EDTA.The former increased DTPA-extractable Cd by 6.06％ ～ 15.64％,while the latter did by 5.74％ ～ 7.16％,8.80％ ～ 10.32％ and 4.77％～ 5.91％,respectively,with DC field on and by 2.84％ ～3.32％,7.70％ ～ 9.47％ and 7.10％～7.75％,respectively,with DC field off.Cd concentration in the plant shoots significantly increased in the pots with DC field on,varying in the range of 226.2 ～ 313.7 mg kg-1,and lingered in the range of 178.7 ～ 212.6 mg kg 1 with DC field off.Soil amendments (pig manure compost,humic acid,EDTA) also had significant effects on Cd concentration in the plant shoots (p ＜ 0.05).In addition,Cd concentration in the plant shoots was increased by 7.33％～ 37.0％,19.0％～ 38.7％ and 6.13％ ～ 12.0％ by the addition of pig manure compost,humic acid and EDTA,respectively.By switching the polarity of the DC electrical field,significant pH variation from anode to cathode can be avoided,and thus no significant impact was observed on shoot biomass of the plants.Soil amendments (pig manure compost,humic acid,EDTA) had significant effects on shoot biomass of the plants (p ＜ 0.05).The addition of 15 g kg-1 pig manure compost and 10 g kg-1 humie acid increased shoot biomass by 40.3％～ 43.7％ and 16.3％ ～ 18.2％,respectively,while the addition of EDTA decreased shoot biomass by 7.3％ ～ 7.5％.Cadmium concentration in shoot and plant shoot biomass are the most crucial factors for determining efficiency of the phytoextraction.The findings in this pot experiment demonstrate that DC field increases significantly (p ＜ 0.01) Cd accumulation in the plants in all the treatments,as compared with those with DC field off.Cd accumulation in shoots of the plants was in the range of 2 088 ～ 4 014 μg pot-1 with DC field on,and 1 677 ～ 2 635 μg pot-1 with DC field off.In addition,Cd accumulation in shoots of the plants was increased by 54.3％ ～ 92.2％ and 38.4％ ～ 63.9％ in the pots pretreated with pig manure compost and humic acid,respectively,because of their simultaneous effects of increasing Cd concentration in shoots and shoot biomass.However,no noticeable effect was observed in the EDTA treatment in comparison with the control,which can be ascribed to the inhibition of plant growth by EDTA.The combined use of pig manure compost-DC field and humic acid-DC field enhanced Cd accumulation in shoots by 134％ and 100％,respectively.Conclusion] Based on the findings,the amendment of pig manure compost or humic acid coupled with switched polarity DC electrical field could significantly enhance Cd phytoextraction by hyperaccumulator Sedum alfredii.