| 微生物诱导碳酸盐岩沉淀过程及作用机理 |
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| 引用本文： | 高旭波,潘振东,龚培俐,江玉,李成城,李鸿煜.微生物诱导碳酸盐岩沉淀过程及作用机理[J].中国岩溶,2022,41(3):441-452. |
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| 作者姓名： | 高旭波 潘振东 龚培俐 江玉 李成城 李鸿煜 |
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| 作者单位： | 中国地质大学(武汉)环境学院, 湖北 武汉 430074 |
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| 基金项目： | 国家自然科学基金项目:地下水系统中碳酸盐岩体系—砷相互作用研究（41877204）；国家自然科学基金青年基金项目:人类活动影响下富钙高氟地下水中氟—钙拮抗的环境生物地球化学过程研究（41902265） |
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| 摘 要： | 微生物诱导碳酸钙沉淀(microbially induced calcium carbonate precipitation, MICP)是一种在自然界中广泛存在的生物矿化过程。由于MICP具有反应速度快、环境条件要求低、应用范围广、温室气体减排效应显著等特点，在地质、土木、水利、环境多个领域中广泛推广应用。文章在分析国内外相关研究成果的基础上，归纳整理出反硝化过程、硫酸盐还原作用、尿素分解作用等多种微生物诱导下碳酸钙矿化途径和作用机制。以尿素分解菌为代表，重点讨论微生物诱导碳酸盐沉淀过程中pH、温度、离子浓度等环境因素对生成矿物晶型晶貌等方面的影响，总结了MICP的环境应用机制，即环境中的重金属元素通过替换作用替换矿化矿物中的Ca2+或CO32?从而被固定。MICP作为一种简单高效的地质环境过程，在生态环境修复领域具有广阔的应用前景。
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| 关 键 词： | 微生物诱导矿化 碳酸钙沉淀 微生物作用机制 尿素分解菌 重金属固定 地质环境修复 |
| 收稿时间： | 2022-01-30 |
Process and mechanism of microbial induced carbonate precipitation |
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| Institution: | School of Environmental Studies, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China |
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| Abstract: | At present, the global ecological environment and geological environment situation is very serious. For environmental heavy metal remediation, traditional physical and chemical remediation methods have been widely used, but the traditional remediation methods have disadvantages such as high cost, high energy consumption, and the use of a large number of chemicals. As a kind of bionic engineering, the principle of biological method is that microorganism fix or degrade pollutants in the environment by microbial metabolic activity.Compared with the traditional physical and chemical methods, biological repair method has lower cost, higher efficiency, and the advantages of green environmental protection,which has been repeatedly proved that can effectively reduce the concentration of heavy metals in the soil and water. Biological mineralization is a kind of biological method, and its main mechanisms include: (1) biologically controlled mineralization; (2) biologically mediated mineralization; (3) biologically induced mineralization, in which Microbially Induced Calcium Carbonate Precipitation (MICP) is one of the main biologically induced mineralization. It is very common in various environments of seawater and sediment, fresh water and soil, and it is a biological mineralization process that exists widely in nature. At the same time, the process has the characteristics of fast reaction speed, low requirements for environmental conditions, wide application range and significant greenhouse gas emission reduction effect, so that it has been widely concerned and popularized in many fields of geology, civil engineering, water conservancy and environment. The research in this field covers the intersection of biological science and inorganic chemistry, biophysics and materials science, etc. The research on biologically induced mineralization and its application in various fields are very remarkable, especially the biologically induced mineralization provides a new idea for environmental remediation. The microbial-induced precipitation of calcium carbonate has been proved for many times to effectively reduce the concentration of heavy metal elements in the environment, and its main action process is as follows: microorganisms produce metabolite CO32? through metabolic activities, and interact with Ca2+ in the environment to form calcium carbonate precipitation under appropriate environmental conditions, and fix heavy metal ions in the environment during the formation of calcium carbonate.Based on the analysis of relevant research results at home and abroad, this paper summarizes the pathway and mechanism of calcium carbonate mineralization induced by various microorganisms, such as denitrification process, sulfate reduction and urea decomposition. In the process of mineralization induced by urea decomposing bacteria, urea is hydrolyzed into carbamate and ammonia under the action of urea decomposing bacteria, and then carbamate spontaneously decomposes to produce ammonia and carbonic acid. The ammonia generated in the reaction hydrolyzes and generates OH?, which increases the pH of the water environment and causes the hydrolysis balance of carbonic acid to move towards the direction of generating carbonic acid, resulting in a large number of carbonic acid ions, which react with the calcium ions existing in the environment and form calcium carbonate precipitation in the supersaturated state. Compared with other MICP mechanisms, urea decomposition process has the advantage of not relying on additional nutrients and producing high concentration of calcium carbonate in a short period of time, so it has attracted more attention and research.It is important to note that minerals induced by microbial mineralization are influenced by environmental factors. In this paper, represented by urea decomposers, the effects of environmental factors such as calcium source, ambient temperature, pH condition and ion concentration on minerals produced by MICP were discussed. The following conclusions are summarized :(1) calcium source affects the morphology, crystal size and morphology of carbonate precipitation and mineral deposition rate; (2) The optimum temperature for the formation and precipitation of urea decomposing bacteria mainly depends on the optimum temperature for bacterial growth and metabolism, which is usually between 20 ℃ and 40 ℃; (3) pH influences the plasma concentrations of HCO3?, CO32? and NH4+ to change the precipitation rate, which directly determines the size of mineral crystals; (4) The presence of other ions in the environment, such as Mg, Ni and Sr, will affect the formation of minerals.Finally, the effects and mechanisms of MICP on reducing the concentration of heavy metal elements in various environments are summarized in this paper. Research show that the process of calcium carbonate induced by urea decomposition can effectively reduce the concentration of heavy metals in the environment, and the fixation rate of copper, cadmium, zinc and other elements is above 90%. The mechanism of action is mainly divided into two kinds, for the heavy metal element like Cu2+, Pb2+ and Zn2+, they are fixed by forming precipitation directly with CO32? or replacing calcium ions in calcium carbonate, while for As and Cr, they will form complex anions such as arsenate in water environment, and will be fixed by substituting carbonate ions from calcium carbonate into the solid. As a simple and efficient geological environment process, MICP has broad application prospects in the field of ecological environment remediation. |
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