植物吸收修复对土壤镍及其主要化学性质的影响

采用室内盆栽试验方法,研究了外源镍污染土壤的植物吸收修复对土壤镍形态和土壤主要化学性质的影响。试验用水稻土添加NiSO4·6H2O(100～1600mgkg-1)经过12周的驯化培养后,种植了镍超累积植物Alyssu mmurale,110 d后收获植物并进行了试验土壤镍的形态和主要化学性质的分析,采用再分配系数和结合强度系数对植物修复效果进行了定量分析。结果表明,根区土壤中DTPA提取态镍的数量明显减少,根区土壤DTPA-Ni与非根区土壤DTPA-Ni之比的范围在0.33～0.61之间。每盆植物提取镍量为6.61～31.18mg,植物提取量随着添加镍量增加而增加,地上部分最大镍含量达到12454.1mgkg-1。根区的再分配系数在2.17～4.19之间,而非根区的再分配系数在6.87～15.91之间,再分配系数随着镍添加量的增加而增大;根区的结合强度系数为0.84～0.39,而非根区的则为0.88～0.26,随着土壤中镍添加量的增加,结合强度系数逐渐减小。植物吸收修复后,根区土壤镍的再分配系数降低、结合强度系数增大,表明土壤镍各形态之间的稳定性增加,因此植物修复可以加快外源镍在土壤中的稳定。试验结果也表明,根区土壤中pH随着镍添加量的增加呈下降趋势、但较非根区土壤的高;根区土壤有机碳亦较非根区的高。

Effects of phytoextraction on added Ni and chief chemical properties in soils

In recent years,phytoremediation using metal hyperaccumulators has been proposed as a cost-effective and environmen- tally-friendly solution to the problem of heavy metal contaminated soils.Researchers have been playing attention on the mechanism of hyperacumulator uptake heavy metals and the biological and chemical effects of heavy metal pollution in soil-plant system.For those purposes,greenhouse pot experiment was employed in this study.Alyssum murale,a species of Ni hyperaccumulators,were planted in soils with 7 different Ni concentrations ranging from 0 to 1 600 mg kg-1 added in the form of NiSO 4to investigate the ef- fects of phytoextraction on Ni fraction redistribution,soil pH and organic carbons.After 110 days of planting,several plant and soil indices,including soil nickel concentration,plant nickel concentration,soil pH values,soil organic carbon,were studied.The results showed that DTPA-Ni in the rhizospheric soils decreased considerably,compare with that in the non-rhizospheric soils.The ratio of DTPA-Ni in the rhizospheric soils to that in the non-rhizospheric soils ranged from 0.33 to 0.61.The amounts of Ni extracted by plants ranged from 6.61mg to 31.18 mg per pot,which had increased with increasing Ni concentrations in soils.The highest concen- tration of Ni in the shoots was 12 454.1 mg kg-1 at 1 600 mg Ni kg-1 treated soil.The redistribution index in the different Ni treated rhizospheric soils ranged from 2.17 to 4.19,which were lower considerably than that in the non-rhizospheric soils,ranged from 6.87 to 15.91.The binding intensity index was lower with increasing the amounts of added Ni,which ranged from 0.84 to 0.39 in rhizospheric soils and from 0.88 to 0.26 in non-rhizospheric soils,respectively.Therefore,phytoextraction can accelerate the stabili- zation of added soluble Ni in soils.Our results also found that,compare with control soils,phytoremediation may raise the soil pH values and the contents of organic carbon in soils.In conclusion,phytoextraction can extract the heavy metal from the contaminated soil and then accelerate metal stabilization in soils.