硫酸盐还原菌对碱性和酸性农田土壤中重金属的钝化效果及其作用机制

Effect and Mechanism of Sulfate-Reducing Bacteria on the Passivation of Heavy Metals in Alkaline and Acidic Agricultural Soils

通过土壤培养实验考察了硫酸盐还原菌(SRB)包括希瓦氏菌、梭状芽胞杆菌和两者混合菌对碱性和酸性农田土中有效态重金属(Cd、Pb、Cu和Zn)的钝化效果及其作用机制.结果表明,在相同接菌量下,希瓦氏菌处理组对碱性土中有效态重金属的钝化效果优于梭状芽胞杆菌和两者混合菌的处理组;而不同种类的SRB对酸性土中有效态重金属的钝化效果无显著差异.培养第20 d后土壤中有效态重金属的钝化率不再显著变化.SRB处理对碱性土中有效态重金属的钝化率可达80%以上,而对酸性土中有效态重金属的钝化率低于40%.在碱性土中,SRB能够有效还原SO_(4)^(2-),并且提高土壤pH值,使S2-可与重金属紧密结合,显著提高有效态重金属钝化率.尽管SRB使酸性土壤pH值升高,但土壤仍然呈酸性使SO_(4)^(2-)还原受到抑制,不利于有效态重金属的钝化.总体来看,SRB适用于碱性和酸性土壤的重金属污染治理,但与酸性土壤相比,SRB对碱性土壤中有效态重金属的钝化效果更好.

The effects of sulfate-reducing bacteria(SRB),including Shewanella JN01,Clostridium ZG01,and their mixture,on the passivation efficiencies and mechanism of available heavy metals(Cd,Pb,Cu,and Zn)in an alkaline and acidic soil were investigated through a soil incubation experiment.The results showed that the passivation efficiencies of available heavy metals in alkaline soil treated by Shewanella JN01 were better than in that treated by Clostridium ZG01 and their mixture when the inoculum size was the same.However,there was no significant difference between the passivation efficiencies in acidic soils that were treated with different types of SRB.The passivation efficiencies of available heavy metals in soil did not obviously change after the 20^(th) day.The passivation efficiencies of available heavy metals in the alkaline soils treated with SRB were greater than 80%,whereas those in the acidic soils were lower than 40%.In the alkaline soil,SRB could effectively reduce SO_(4)^(2-)and increase soil pH,which resulted in the tight bonding of S^(2-) with available heavy metals to evidently improve the passivation efficiencies of available heavy metals.Although the pH of acidic soil increased after inoculation with SRB,the reduction of SO_(4)^(2-)was inhibited because of the acidic condition in the soil,which was unfavorable for the passivation of available heavy metals.Collectively,SRB could be used to remediate the alkaline and acidic soils contaminated with heavy metals.Nevertheless,the passivation effect of SRB on available heavy metals in alkaline soil was better than those in acidic soil.