【作者】 黄楠；

【导师】 薛生国；

【作者基本信息】 中南大学 ， 冶金环境工程， 2022， 博士

【摘要】 赤泥是氧化铝冶炼过程中排放的固体废弃物,碱性强、盐分高、综合利用难,迄今尚无经济可行的规模化处置方法。大量外排赤泥贮存于赤泥堆场,特殊气象条件下可能产生扬尘、碱性渗漏液造成环境污染,而且存在溃坝安全隐患,生态修复是降低赤泥堆场环境安全风险的有效途径。然而,赤泥特殊的理化性质导致堆场难以支持植物生长,需要通过基质改良等措施,驱动赤泥土壤化过程,以期促进赤泥堆场植被重建。论文通过在我国代表性赤泥堆场开展生态调查,分析不同年限赤泥堆场的自然成土过程,调查堆场及周边区域植物多样性和微生物群落多样性,筛选出一株耐盐碱细菌并分析其强盐碱环境条件下的产酸过程,结合模拟实验探讨了耐性植物-功能微生物联合作用对赤泥理化性质、微生物群落结构和植物抗逆性的影响,为赤泥土壤化及堆场生态修复提供科学依据。主要研究结果如下:（1）赤泥自然成土过程中,碳磷比和氮磷比逐渐增加,碳氮磷生态化学计量比逐渐趋近堆场周边土壤。新堆存赤泥（小于1年）表层微生物量碳氮磷含量分别为11.09 mg/kg、2.13 mg/kg和0.48mg/kg;堆存18年后,分别增至141.2 mg/kg、24.4 mg/kg和4.59mg/kg。赤泥堆存18年后,开始出现先锋植物入侵,草本植物为优势种,主要分布在禾本科、菊科、藜科,约占82%。赤泥堆场生长的先锋植物物种中,狗牙根（Cynodon dactylon）、虎尾草（Chloris virgata）、马唐（Digitaria sanguinalis）、高羊茅（Festuca arundinacea）对盐分离子富集能力和转运能力较强。先锋植物对赤泥主要可交换态盐基离子的转运能力依次为K>Ca>Mg>Na。结合植物多样性调查及耐性特征研究结果,狗牙根和高羊茅可作为赤泥堆场生态修复的先锋植物。（2）赤泥堆场自然恢复过程中,微生物生物量和酶活性显著升高,与赤泥p H、电导率、钠离子含量等盐碱性指标呈显著负相关关系;细菌群落丰富度和多样性指数也显著升高,门水平优势菌群为变形菌门（Proteobacteria）、酸杆菌门（Acidobacteria）、拟杆菌门（Bacteroidetes）和放线菌门（Actinobacteria）。有机碳（TOC）、总氮（TN）和p H是赤泥堆场微生物群落演替的主要驱动因子,降低盐碱性、增加肥力有助于丰富赤泥堆场细菌群落多样性。（3）从赤泥堆场上的植物生长区采集赤泥,通过对土著微生物进行菌株分离,筛选出一株耐盐碱产酸细菌,能够适应极端环境条件并通过产酸缓解盐碱胁迫。经过微生物鉴定,细菌为金云苏芽孢杆菌。最优产酸条件初始p H=9、盐浓度0.8%,以葡萄糖为碳源、蛋白胨为氮源,培养11天时,芽孢杆菌生物量达到最大值,培养基p H降低至3.6。（4）添加质量比2%的石膏对赤泥进行基质改良,随后使用生物改良对赤泥进一步处理。结果表明,狗牙根/高羊茅种植后,赤泥p H降低至8左右,碳氮磷等养分含量明显增加,赤泥理化性质满足堆场生态修复要求。与单独植物种植相比,芽孢杆菌菌液添加显著提高赤泥微生物生物量和酶活性。菌液添加后,赤泥微生物群落多样性显著提高,根瘤菌科（Rhizobiaceae）、鞘杆菌科（Sphingobacter）、假单胞菌科（Pseudomonadaceae）、黄单胞菌科（Xanthomonadaceae）、腐生螺科（Saprospiraceae）和黄杆菌科（Flavobacteriaceae）等菌群丰度增加,微生物生态功能发生明显变化。（5）施用芽孢杆菌后,高羊茅/狗牙根地上部和根部组织中丙二醛、O₂^-和H₂O₂等活性氧组分含量显著降低（p<0.05）,而超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶等抗氧化酶活性显著增加（p<0.05）。这表明芽孢杆菌能够有效促进高羊茅/狗牙根体内抗氧化酶表达,减轻赤泥盐分离子对植物的毒性作用。高羊茅/狗牙根-芽孢杆菌可作为赤泥成土驱动和堆场生态修复的组合配置模式。图47幅,表23个,参考文献245篇更多还原

【Abstract】 Bauxite residue is the solid waste generated during alumina extraction.It is high alkaline and saline,which is difficult to utilize.Currently,the majority of the bauxite residue is stored in disposal areas（bauxite residue disposal areas,BRDAs）,not only occupying land resources,but also possessing relatively serious environmental risks to surrounding areas.Recently,the ecological disposal of bauxite residue has attracted the attention in the academia and industry field.The transformation of bauxite residue into soil-like materials is the promising way forward to remediate the residues on a large scale and reduce potential environmental risks.Microbial communities are an important component of terrestrial ecosystems and directly affect the geochemical cycle and the soil formation of bauxite residue,which has been largely neglected.In this paper,the evolution of microbial communities and its potential functions during soil formation in bauxite residue were studied by the combination of field investigation and soil cultivation experiments.The main conclusions are as follows:（1）During the natural soil formation of bauxite residue,the ratio of carbon to phosphorus and the ratio of nitrogen to phosphorus gradually increased,and the ecostoichiometric ratio of carbon to nitrogen and phosphorus of red mud gradually approached the soil near the BRDAs.The contents of carbon,nitrogen and phosphorus on the surface of the newly stacked bauxite residue（stacked for less than 1 year）were 11.09 mg/kg,2.13 mg/kg and 0.48 mg/kg,respectively,and increased to 141.2 mg/kg,24.4 mg/kg and 4.59 mg/kg after 18 years stacked.After 18 years,pioneer plants invaded the BRDAs,and herbaceous plants were the dominant species.The enrichment coefficients of K,Ca,Na,Mg of the four salt ions in dominant plants ranged from large to small K（0.84）>.Ca（0.73）>Mg（0.54）and Na（0.28）,and the enrichment ability of K and Ca in dominant plants was higher than that of Mg and K.The transport coefficient of the dominant plants to the four salts was K（1.04）>Ca（0.87）>Mg（0.62）>Na（0.32）,and the enrichment ability of K and Ca in dominant plants was higher than that of Mg and K.Rhizoctonia dactyloides,Herba virginis,Digitaria sanguinalis and Festuca arundinacea have strong ability of salt ion enrichment and transport,and belong to the enrichment plants.Based on the comprehensive consideration of the salt content,enrichment coefficient and transport coefficient in plants,it is concluded that Digitaria sanguinalis and Festuca arundinacea have a good ability to enrich salt ions in bauxite residue,so they can be used as the pioneer plants in BRDA remediation.（2）Compared with fresh residue,the physical and chemical properties of the rhizosphere areas were improved.The microbial biomass,enzyme activity and bacterial community richness and diversity were increased significantly.Proteobacteria,Acidobacteria,Bacteroidetes and Actinobacteria were the dominated taxonomy group.Organic carbon,total nitrogen and p H were the main driving factors of bacterial community in the process of natural formation of bauxite residue.（3）Collected bauxite residue from the plant growth area on BRDA,isolate strains of indigenous microorganisms,and screened out a salt alkali tolerant acid-producing bacterium that can adapt to strong alkaline conditions and alleviate salinity stress through acid production.The salt alkali resistant bacteria were identified as Bacillus thuringiensis.The optimal acid production conditions include an initial p H of 9 and a salt concentration of 0.8%.When cultured with glucose as a carbon source and peptone as a nitrogen source for 11 days,the biomass of the bacillus reached its maximum,and the p H of the culture medium was reduced to3.6.（4）Gypsum was added at a ratio of 2%to reduce the alkalinity of bauxite residue.Next,use a combination of plants and microorganisms to improve the bauxite residue.The results showed that after planting Cynodon dactylon/Festuca arundinacea,the p H of the bauxite residue decreased to about 8,and the nutrient components such as carbon,nitrogen,and phosphorus significantly increased,and the physicochemical properties of the bauxite residue met the requirements of ecological restoration of the BRDAs.Compared with single plant cultivation,the addition of bacillus significantly increased the microbial biomass and enzyme activity of the bauxite residue.The microbial community diversity of the bauxite residue was significantly increased,and the abundance of bacterial groups such as Rhizobiaceae,Sphingobacter,Pseudomonadaceae,Xanthomonadaceae,Saprospiraceae,and Flavobacteriaceae increased,and the ecological functions of the microorganisms changed significantly.（5）After the addition of Bacillus subtilis,the contents of active oxygen components such as malondialdehyde,O₂^-,and H₂O₂ in the aboveground and underground tissues of Cynodon dactylon/Festuca arundinacea were significantly reduced（p<0.05）,while the activities of antioxidant enzymes such as superoxide dismutase,peroxidase,catalase,and ascorbate peroxidase were significantly increased（p<0.05）.This indicates that Bacillus subtilis can effectively promote the expression of antioxidant enzymes in Cynodon dactylon and Festuca arundinacea,and alleviate the toxic effects of bauxite residue salinity on plants.The combined action of plants and microorganisms can improve the succession of microbial community and accelerate the soil generation process of bauxite residue.Compared with the natural weathering process of bauxite residue,human disturbance can reduce the salinity of bauxite residue in a short time,improve the physical and chemical properties of bauxite residue,increase the richness and diversity of bacterial community,and promote the soil generation of bauxite residue and the ecological restoration of the storage site.更多还原