“双耐”细菌-香根草对铅镉复合污染土壤的修复机理

Remediation mechanism of "double-resistant" bacteria- Vetiveria zizanioides on Cd and Pb contaminated soil

将"双耐"细菌与重金属富集植物——香根草构建修复体系,探讨其对铅(Pb)、镉(Cd)复合污染土壤的联合修复效应.试验为双因素完全随机区组试验,A因素为铅镉污染浓度,设置6个水平,即Cd0Pb0、Cd10Pb400、Cd20Pb800、Cd40Pb1200、Cd60Pb1600、Cd80Pb2000(数据单位为mg/kg).B因素为K7菌加菌量,设置3个水平,加菌量为0、1.5、3.0 g.结果表明:(1)"双耐"细菌能提高香根草的生物量.当处理为Cd10Pb400加菌1.5 g时,提高3.9%;当Cd40Pb1200加菌1.5 g时,提高13.2%,加菌量为3.0 g时增加30.46%;当Cd60Pb1600加菌1.5 g时,提高9.46%;当Cd80Pb2000加菌3.0 g时,提高7.02%.(2)"双耐"细菌对香根草地上和地下部铅、镉的吸收具有促进作用.当土壤中铅含量<1 200 mg/kg,加菌量1.5 g的香根草地上铅含量分别提高了1.9 mg/kg(Cd10Pb400)、3.6 mg/kg(Cd20Pb800)、4.1 mg/kg(Cd40Pb1200).对于镉而言,当加菌量为1.5 g时,地上部镉含量分别升高了314.7%(Cd10Pb400)、4 1.7%(Cd20 Pb800)、35.1%(Cd20Pb800)、103.5%(Cd40Pb1200)、57.8%(Cd6 0Pb1600).加菌后根部铅含量大于不加菌的根部铅含量,Cd40Pb1200处理时,根部铅浓度最大.相同铅、镉浓度处理时,加菌量为3.0 g的香根草根部镉含量比加菌量1.5 g的根部镉含量高.(3)加菌后的香根草根际土有效态铅、镉含量比不加菌的浓度低.香根草根际土有效态铅含量下降幅度最大的处理是Cd20Pb800加菌1.5 g,与对照组相比降低了30.22%.相同污染条件下,加菌3.0 g香根草根际土有效态镉含量最低."双耐"菌强化香根草修复铅镉污染土壤的机理可为修复铅镉污染土壤的实际应用提供理论依据和技术参考.

Microbe-plant combined remediation of soil contaminati on by heavy metals has being an important part of soil and environmental sciences.This study was conducted to explore the remediation effect of the system of ＂double-resistant＂ bacteria and heavy metal enrichment plant vetiver on the lead（Pb） and cadmium（Cd） contaminated soil.We used twofactor randomized complete block experiment.Factor A was the contamination of lead and cadmium,at six levels of Cd0Pb0,Cd10Pb400,Cd20Pb800,Cd40Pb1200,Cd60Pb1600 and Cd80Pb2000（data in units of mg/kg）.Factor B was the amount of bacteria K7,at three levels of 0,1.5,and 3.0 g,respectively.The experiment found that the ＂double-resistant＂ bacteria could promote the growth of vetiver.Under the condition of 10 mg/kg of Cd2＋ and 400 mg/kg of Pb2＋,addition of 1.5 g ＂double resistant＂ bacteria increased the vetiver biomass by 3.9%;with 40 mg/kg Cd2＋ and 1 200 mg/kg of Pb2＋,addition of 1.5 g bacteria increased the biomass by 13.2%,and that of 3.0 g bacteria increased it by 30.46%;with 60 mg/kg of Cd2＋ and 1 600 mg/kg of Pb2＋,addition of 1.5 g bacteria increased the biomass by 9.46%;with 80 mg/kg of Cd2＋ and 2 000 mg/kg of Pb2＋,addition of 3.0 g bacteria increased the biomass by 7.02%.＂Double-resistant＂ bacteria could stimulate the absorption of Pb and Cd by both aboveground and underground part of Vetiveria zizanioides.With soil Pb2＋ below 1200mg/kg,addition of 1.5 g bacteria increased the aboveground Pb content in V.zizanioides by 1.9 mg/kg for 10 mg/kg of Cd2＋ and 400 mg/kg of Pb2＋,by 3.6 mg/kg for 20 mg/kg of Cd2＋ and 800 mg/kg of Pb2＋,by 4.1 mg/kg for 40 mg/kg of Cd2＋ and 1 200 mg/kg of Pb2＋.The addition of 1.5 g bacteria increased the aboveground Cd content in V.zizanioides by 314.7%（Cd10Pb400）,41.7%（Cd20Pb800）,35.1%（Cd20Pb800）,103.5%（Cd40Pb1200）,57.8%（Cd60Pb1600）,respectively.The Pb content in the vetiver root was higher with ＂double-resistant＂ bacteria additon,being the maximum with 40 mg/kg of Cd2＋ and 1 200 mg/kg of Pb2＋ in soil.With the same Pb and Cd concentrations in soil,addition of 3.0 g bacteria was related to higher Cd content in the root than that of 1.5 g resistant strain.Addition of the bacteria also lowered the effective contents of Pb and Cd in the rhizosphere soil,with the maximum of decrease of Pb in rhizosphere soil（30.22% lower than control） with 20 mg/kg of Cd2＋,800 mg/kg of Pb2＋,and 1.5 g bacteria addition in soil;under the same condition,the Cd content was the lowest with addition of 3.0 g ＂double-resistant＂ bacteria.The mechanism of ＂Double-resistant＂ bacteria strengthen vetiver repairing of lead and cadmium contaminated soils was explained in this paper,providing a theoretical basis and practical application of technical reference for the repairing of lead and cadmium contaminated soil.