【作者】 王宁；

【导师】 张世敏；

【作者基本信息】 河南农业大学 ， 微生物学， 2021， 硕士

【摘要】 目前我国镉污染严重,在石灰性土壤中小麦镉超标问题时有发生,因此对镉污染土壤的修复迫在眉睫。重金属钝化技术在近几十年的研究中,取得了很大的成就与进展,很多研究发现含磷材料在固定土壤中的重金属有良好的效果。但大多研究只针对于酸性土壤,对于北方石灰性土壤镉污染修复鲜有研究。本研究采用盆栽实验分析了镉胁迫下小麦根际细菌群落结构,并建立了镉钝化剂的快速筛选方法,研究了含磷钝化材料对小麦镉积累和生长的影响,并评价了其对小麦根际微生物群落的影响。主要结论如下:（1）镉胁迫显著抑制了小麦生物量,增加了土壤中有效镉含量。此外,镉胁迫增加了细菌的物种数量,并改变了细菌的群落结构,其中占据主导地位的门主要为变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）等;而占据主导地位的属主要为鞘氨醇单胞菌属（Sphingomonas）、unidentified＿Acidobacteria、溶杆菌属（Lysobacter）。与对照相比,鞘氨醇单胞菌（Sphingomonas）等根际促生菌属丰度在Cd胁迫下有所减小。由此可见,镉本身的毒性以及鞘氨醇单胞菌丰度的减小有可能是抑制小麦生长的的重要原因。（2）建立了钝化剂的快速筛选方法,并发现羟基磷灰石（HAP）、磷酸氢二钾（K₂HPO₄）、磷酸钙（Ca₃（PO₄）₂）、磷酸氢二铵（（NH₄）₂HPO₄）、磷酸二氢钾（KH₂PO₄）5种含磷材料均可降低镉的有效性,其中HAP、Ca₃（PO₄）₂和KH₂PO₄效果最好,可使有效镉含量降低幅度为16.63%～31.28%。通过盆栽实验发现,施加Ca₃（PO₄）₂和KH₂PO₄均提高了小麦生物量和磷含量,且均降低了小麦植株镉含量,以施加量为50 mg·kg^-1的KH₂PO₄处理降镉最佳,使小麦地下部、地上部镉含量和镉吸收总量较对照分别显著降低了28.37%、18.84%和12.72%。除施加量为200 mg·kg^-1的KH₂PO₄处理,其它各处理均提高了土壤p H,其中以施加量为50 mg·kg^-1的KH₂PO₄处理提升土壤p H最高,达到8.49,较对照提高了0.18个单位。由此可见,Ca₃（PO₄）₂和KH₂PO₄可通过提高p H的机制实现了镉的钝化,从而抑制了小麦镉积累。（3）通过分析含磷钝化剂对土壤碱性磷酸酶活性的影响发现,除施加量为200 mg·kg^-1的KH₂PO₄处理外,其它各处理均不同程度减弱了土壤碱性磷酸酶活性,其中以施加量为50mg·kg^-1的KH₂PO₄处理降低幅度最大,降低了5.45%。同时,通过分析含磷钝化剂对土壤微生物群落结构的影响发现,Ca₃（PO₄）₂和KH₂PO₄均不同程度的提高了真菌和放线菌的数量,显著降低了细菌的数量。通过高通量16S r RNA基因测序发现,施用KH₂PO₄显著减少了土壤细菌的多样性,改变了细菌的群落结构。在属水平,乳杆菌属（Lactobacillus）等产酸菌丰度的降低,是影响土壤p H、有效镉含量变化的重要原因。且杜氏藻属（Dubosiella）、Sh765B-Tz T-35等对植物生长有益菌属的提升,是影响小麦生长重要原因。这些研究结果为采用钝化技术修复石灰性土壤镉污染提供了理论依据和技术支撑。更多还原

【Abstract】 At present,my country’s cadmium pollution is serious,and the problem of wheat cadmium exceeding the standard in calcareous soil occurs from time to time.Therefore,the restoration of cadmium contaminated soil is urgent.In recent decades,heavy metal passivation technology has made great achievements and progress.Many studies have found that phosphorus-containing materials have good effects in fixing heavy metals in soil.However,most studies only focus on acidic soils,and there are few studies on the remediation of cadmium pollution in calcareous soils in northern China.In this study,a pot experiment was used to analyze the bacterial community structure in the rhizosphere of wheat under cadmium stress,and a rapid screening method for cadmium inactivators was established.The effect of phosphorus inactivation materials on the accumulation and growth of cadmium in wheat was studied,and its effect was evaluated.The influence of wheat rhizosphere microbial community.The main conclusions are as follows:(1)Cadmium stress significantly inhibited wheat biomass and increased the available cadmium content in the soil.In addition,cadmium stress increases the number of bacterial species and changes the community structure of bacteria.The dominant phyla are Proteobacteria,Actinobacteria,Acidobacteria,etc;The dominant genera are mainly Sphingomonas,unidentified_Acidobacteria,and Lysobacter.Compared with the control,the abundance of rhizosphere growth-promoting bacteria such as Sphingomonas was reduced under Cd stress.It can be seen that the toxicity of cadmium itself and the decrease in the abundance of Sphingomonas may be important reasons for inhibiting the growth of wheat.(2)Established a rapid screening method for passivating agents,and found that hydroxyapatite(HAP),dipotassium hydrogen phosphate(K2HPO4),calcium phosphate(Ca3(PO4)2),diammonium hydrogen phosphate((NH4)2HPO4),potassium dihydrogen phosphate(KH2PO4)five phosphorus-containing materials can reduce the effectiveness of cadmium,of which HAP,Ca3(PO4)2 and KH2PO4 have the best effects,reducing the effective cadmium content by 16.63%~31.28%.Through pot experiments,it was found that the application of Ca3(PO4)2 and KH2PO4 both increased wheat biomass and phosphorus content,and both reduced the cadmium content of wheat plants.The application of 50 mg·kg-1 KH2PO4 treatment reduced cadmium optimally,which made the wheat The cadmium content and total absorption of cadmium in the underground and above ground were significantly lower than the control by 28.37%,18.84% and 12.72%,respectively.Except for the KH2PO4 treatment with an application amount of 200 mg·kg-1,all other treatments increased the soil p H.Among them,the KH2PO4 treatment with an application amount of 50mg·kg-1 increased the soil p H the highest,reaching 8.49,which was an increase of0.18 units compared with the control.It can be seen that Ca3(PO4)2 and KH2PO4 can inactivate cadmium through the mechanism of increasing p H,thereby inhibiting the accumulation of cadmium in wheat.(3)Through analyzing the influence of phosphorus-containing deactivator on soil alkaline phosphatase activity,it was found that,except for the KH2PO4 treatment with an applied amount of 200 mg·kg-1,the other treatments all weakened the soil alkaline phosphatase activity to varying degrees.The KH2PO4 treatment with an applied amount of 50 mg·kg-1 decreased the most,with a decrease of 5.45%.At the same time,by analyzing the influence of phosphorus-containing deactivator on the structure of soil microbial community,it was found that both Ca3(PO4)2 and KH2PO4 increased the number of fungi and actinomycetes to varying degrees,and significantly reduced the number of bacteria.Through high-throughput 16 S r RNA gene sequencing,it was found that the application of KH2PO4 significantly reduced the diversity of soil bacteria and changed the bacterial community structure.At the genus level,the decrease in the abundance of acid-producing bacteria such as Lactobacillus is an important reason that affects the changes in soil p H and effective cadmium content.Moreover,the promotion of beneficial bacteria such as Dubosiella and Sh765B-Tz T-35 for plant growth is an important reason for affecting wheat growth.These research results provide theoretical basis and technical support for the use of passivation technology to remediate cadmium pollution in calcareous soil.更多还原