赤泥添加对石灰性土壤中Pb、Cd形态分布及小麦根系的影响

Effects of red mud addition on fractions of Cd,Pb and wheat root growth in calcareous soil

通过田间种植小麦实验,研究添加不同剂量拜耳赤泥(0%、1%、2%、3%、4%和5%)对重金属污染的石灰性土壤Pb、Cd化学形态和小麦幼苗根系的影响。培养1个月,添加赤泥显著地提高了土壤p H值,提高幅度随赤泥投加量增加而增大。培养3个月,添加不同剂量的赤泥均明显降低土壤中可交换态Pb和Cd的含量,赤泥投加量为5%时效果最为显著,分别比对照下降90%和72%。添加赤泥对所种植小麦幼苗的根系也有影响。种植5个月,小麦根系总根长、总表面积和总体积等随添加赤泥的剂量增加呈现先增大后减小的趋势,赤泥投加量为3%时增幅最大,总根长、总表面积和总体积分别比对照增加88.23%、75%和90.32%。研究表明,赤泥可作为重金属污染的石灰性土壤的理想改良剂,但考虑到小剂量赤泥(即1%~3%)促进重金属污染农田中小麦根系的生长,建议在种植区采用小剂量赤泥(即3%)处理的重金属污染修复方案。

The effects of adding red mud into the soil（ with dosages of 0%,1%,2%,3%,4%,and 5%） on wheat seedling roots and on fractionation of Cd and Pb in soil were determined in a field experiment. The addition of red mud increased the soil p H after one month of incubation and the effect was enhanced with higher red mud dosage. Adding red mud with different dosages significantly decreased the concentration of exchangeable Pb and Cd after three months of incubation. Compared with the control sample,the concentration of exchangeable Pb and Cd decreased by 90% and 72% by adding red mud with a dosage of 5%,respectively. Amendments of red mud with different dosages had different effects on the wheat seedling roots. The length,surface area,and volume of the wheat seedling roots increased with the increase in red mud dosage from 1% to 3% at the fifth month of the wheat growth,and then declined with an increase in the red mud dosage from 3% to 5%. Compared with the control,the length,surface area,and volume of the roots increased by 88. 23%,75. 00%,and 90. 32%,respectively,by adding red mud with the dosage of 3%. In conclusion,red mud effectively immobilized Pb and Cd in soil. However,since small doses（ 1% to 3%） of red mud promoted the development of wheat seedling roots planted in heavy-metal-contaminated soil,the addition of red mud with a dosage of 3% would be more effective for plant growth in agricultural soils.