南方离子型稀土开采对土壤微生物及其氨氧化作用的影响研究

The exploitation of rare earth resources causes serious environmental pollution to the ecological environment of mining areas, which attracts much attention. Soil microorganisms, especially ammonia oxidizing microorganisms, play a very important role in the soil ecosystem. However, the effects of rare earth mining on soil microorganisms and ammonia oxidation are still unclear. Therefore, this project will use four different types of soil which are in the in-situ leaching ionic rare earth mining area of the southern Jiangxi Province, as the research object. We plan to carry out the following research work. ICP-MS will be used to determine the contents of available states of rare earth elements and the total amounts of heavy metals, which will reveal the characteristics and pollution status of soil caused by rare earth mining. Illumine Miseq sequencing and bioinformatics analysis will be used to establish the index system of soil characteristics and microbial community composition, to reveal the effect of rare earth mining on soil microbes. DCD (dicyandiamide) microcosm incubation and the stable isotope labeling incubation, using DNA-SIP combined with molecular biology techniques, will evaluate the correlation between soil characteristics and nitrification of the mining soil. These results will also clarify the metabolically active ammonia oxidizers in different types of mining soil and illustrate the influence on the ammonia oxidation as a result of the rare earth exploiting. A variety of statistical evaluation indexes will be used to assess the micro ecological risk of mining soil. This project will provide a theoretical basis for the scientific assessment of the destruction of soil ecological environment and ecological risk caused by ionic rare earth mining.

南方离子型稀土资源开发对矿区生态环境污染严重，备受关注。土壤微生物，尤其是氨氧化微生物对矿区土壤生态系统起着重要作用，但稀土开采对土壤微生物及其氨氧化作用的影响尚不明确。本项目拟采用赣南离子型稀土矿区4种类型土壤为研究对象，采用ICP-MS测定稀土有效态含量及重金属总量，揭示稀土开采导致的土壤环境变化特征和污染状况；采用illumina Miseq测序结合生物信息学分析，建立矿区土壤特性和微生物群落组成特性之间的关联指标体系，揭示稀土开采对土壤微生物的影响；通过DCD微宇宙培养试验和稳定态同位素标记培养试验，采用DNA-SIP结合分子生物学技术，评估土壤特性与硝化作用相关性，揭示各类型土壤中功能活跃的氨氧化微生物类群，阐明稀土开采对土壤氨氧化作用及其微生物的影响；采用各种统计学评价指标，评估矿区土壤的微生态风险。本项目将为科学评估离子型稀土开采对土壤生态环境的破坏及其生态风险提供理论依据。

南方离子型稀土资源开发对矿区土壤及周边污染严重。但稀土开采对土壤微生物及其氨氧化作用的影响尚不明确。本项目以离子型稀土采矿区土壤、原矿土壤和矿区周边土壤为研究对象，发现开采活动不仅造成了土壤酸化，改变了土壤稀土元素赋存形态，而且增加了周边土壤氨氮和稀土元素含量，造成了周边区域土壤污染。pH和弱酸提取态稀土显著影响采矿土壤细菌物种丰富度，古菌群落结构较为稳定，与环境因子相关性不显著。相关性网络分析表明采矿活动使得细菌种群间相互作用增强，古菌间相互作用减弱。真菌多样性与丰度受到矿区土壤有机物，TC和TN显著影响，腐生营养型和共生营养型真菌丰度较高，能够为土壤提供养分来源。三种类型土壤中氨氧化古菌（AOA）丰度显著高于氨氧化细菌（AOB），且大多数土壤样品中难以检测到AOB。Thaumarchaeota（奇古菌门）是矿区土壤中最主要的AOA门类，但大多数难以进行更细致的分类；AOB属于β-变形菌纲。DMPP微宇宙培养实验表明，原矿、开采矿区和短期停用矿区土壤中，Nitrososphaera属和未分类的AOA在氨氧化作用中起主导作用。长期停矿区域，由于土壤pH值相对较高，AOB也在硝化作用中发挥了一定的作用。对三种类型土壤进行肥力和金属污染风险评价表明，稀土矿区及周边土壤因采矿活动强烈干扰，土壤肥力处于低下水平；矿区金属污染主要由稀土元素直接及间接潜在作用导致，周边土壤金属地积累指数评级不高，但也存在潜在的金属污染风险。土壤地球化学特性之间的相关性分析表明，土壤稀土生物有效性、赋存形态受土壤 pH、氨氮、含水量和TC含量的调控，环境条件的改变可能导致其从残渣态转化成可迁移形态，对矿区及周边土壤生态安全产生威胁。本项目为科学评估离子型稀土开采对土壤生态环境的破坏及其生态风险提供了理论依据。