水稻土中微生物发酵过程对氧化铁还原的贡献

发布时间：2018-01-10 22:19

  本文关键词：水稻土中微生物发酵过程对氧化铁还原的贡献　出处：《西北农林科技大学》2017年博士论文　论文类型：学位论文

  更多相关文章： 氧化铁还原 水稻土有机质 pH 微生物群落结构 微生物发酵产氢 生物炭

【摘要】：水稻土中氧化铁还原过程与稻田中碳、氮、硫、磷等元素的地球化学循环密切相关,Fe(Ⅲ)还原过程同时偶联有机污染物的降解及变价重金属的氧化还原过程,对稻田产甲烷过程产生显著的抑制作用,因此研究淹水稻田中Fe(Ⅲ)还原过程及其机理具有重要的地球化学和环境学意义。早先对Fe(Ⅲ)还原过程的认知主要集中在沉积物环境中,大量的研究证实氧化铁的异化还原过程是沉积物等厌氧环境中Fe(Ⅲ)还原的主要方式,而兼性共代谢还原过程往往与有机质的厌氧分解相偶联,被认为是Fe(Ⅲ)还原的次要途径。然而与沉积物长期处于厌氧环境不同,稻田水旱轮作的耕作方式所形成的氧化还原环境交替,使得微生物代谢有机质产氢过程成为电子传递链中的重要环节。因此有关淹水稻田中微生物发酵有机质进行兼性共代谢还原氧化铁的机理还有待进一步深入。本研究采用厌氧恒温培养方法,采集我国不同植稻区的典型水稻土,比较不同水稻土理化性质和Fe(Ⅲ)还原特征的差异,揭示影响淹水稻田中Fe(Ⅲ)还原过程的主要因素;通过外源添加不同的小分子有机碳源和调节土壤pH条件,研究有机质厌氧发酵过程中微生物群落结构、脱氢产氢过程和Fe(Ⅲ)还原过程之间的相互关系,揭示微生物发酵过程中产生小分子有机碳、产氢、产酸对Fe(Ⅲ)还原过程的作用;通过荧光激发-发射光谱扫描研究不同水稻土中水溶性有机碳的荧光特性及主要组分,揭示水溶性有机质与Fe(Ⅲ)还原过程的关系;以生物炭为载体,利用其具有高含量的芳香结构和较强的吸附能力这一特点,采用低分子量有机碳修饰生物炭,研究其在促进水稻土Fe(Ⅲ)还原过程方面的潜能,从而将水溶性有机碳的电子传递功能和微生物发酵有机物对Fe(Ⅲ)还原的贡献这一理论应用于实践。主要的研究结果如下:(1)水稻土淹水后,Fe(Ⅱ)随淹水时间延长而逐渐累积,不同水稻土间Fe(Ⅲ)还原特征存在显著差异。在土壤理化性质中,有机质含量和无定形氧化铁含量是决定Fe(Ⅲ)还原特征的最主要因素,二者均与Fe(Ⅲ)还原潜势a和最大Fe(Ⅲ)还原速率Vmax间存在显著的正相关关系,而pH是影响达到最大Fe(Ⅲ)还原速率所需时间的主要因素。(2)水稻土中Fe(Ⅲ)还原过程对不同种类碳源调控的响应因土壤不同而存在明显差异。微生物利用葡萄糖引起的土壤pH降低抑制了酸性水稻土中的Fe(Ⅲ)还原过程。水稻土中微生物利用不同种类碳源为底物的发酵脱氢产氢过程主要出现在培养初期,产氢能力从强到弱依次为葡萄糖丙酮酸盐乳酸盐,且脱氢酶活性最大值对应的时间与微生物铁Fe(Ⅲ)原反应达到最大反应速率的时间(TVmax)具有一致性。培养体系中pH的降低表明H+的产生是微生物发酵有机碳源的主要产物,以Fe(OH)3为电子受体的还原过程显著消耗了微生物利用不同种类碳源发酵产生的的h2。培养体系ph与h2分压和fe(ii)累积量存在极显著负相关关系,说明微生物利用有机碳源发酵产生有机酸、进而影响脱氢产氢特性并作用于微生物fe(iii)还原过程。(3)随着可利用营养基质和铁受体的消耗,淹水水稻土中的微生物群落和潜在fe(iii)还原菌呈现出了显著的演替。其中firmicutes是最为优势的类群,随着淹水时间延长相对丰度逐渐降低;acidobacteria、bacteroidetes、chloroflexi、proteobacteria和ignavibacteriae是第二大类优势群,相对丰度均随淹水时间延长而逐渐升高。外源添加不同浓度葡萄糖为微生物提供了充足的碳源,使微生物群落演替滞后,从而使firmicutes大量富集,尤其是具有发酵产氢功能的clostridium和bacillus,且该滞后效应因碳源浓度的增加而增强。不同浓度葡萄糖富集下水稻土中形成以bacillus和clostridium为主、desulfitobacterium、solibacillus、anaeromyxobacter和paenibacillus等为辅的潜在fe(iii)还原菌群。结合添加不同浓度葡萄糖时微生物脱氢产氢特性和fe(iii)还原特征,验证了不同浓度葡萄糖调控下潜在fe(iii)还原菌群落结构变化与脱氢产氢过程对bacillus和clostridium群落结构变化的响应共同作用而影响fe(iii)还原过程。(4)调控水稻土初始ph使脱氢产氢过程中微生物活性、相应酶活性及fe(iii)溶解性发生改变而进一步作用于fe(iii)还原过程。当调节酸性和碱性性水稻土初始ph至强酸性或酸性时,淹水培养过程中脱氢酶活性受到显著抑制,在碱性水稻土中产氢过程受到抑制而酸性水稻土中得以促进。虽然在此情况下酸溶性fe(iii)的浓度较未调节处理显著提高,但fe(iii)还原过程仍然受初始ph降低的抑制,因此在低ph条件下铁氧化物的溶解性并非是影响fe(iii)还原过程的主要因素。调节水稻土初始ph至中性、碱性及强碱性时,微生物的脱氢反应及fe(iii)溶解性不受ph调节影响,其中碱性水稻土调节至中性和酸性水稻土调节至中性、碱性及强碱性时氢气分压显著降低,使fe(iii)还原提前达到最大反应速率,体现出fe(iii)还原过程对氢气的利用和消耗。在不同初始ph水稻土fe(iii)还原的快速时期,可以表征代谢有机质微生物的活性的脱氢酶与fe(ii)累积密切相关。(5)水稻土中微生物对土壤有机质发酵的脱氢产氢过程和潜在fe(iii)还原菌群落结构对初始ph调节的响应直接或间接地影响着水稻土中的fe(iii)还原过程。当调节酸性水稻土至碱性后细菌群落结构受ph调节影响较小,淹水初期firmicutes受初始ph调节相对丰度有所提高。碱性水稻土中proteobacteria占细菌的比例随初始ph调节至酸性而升高,细菌群落结构因ph调节而存在较大差异。酸性水稻土中潜在fe(iii)还原菌相对丰度较未调节处理有所提高,对应于提高的fe(iii)还原对h2的消耗和提前达到的最大fe(iii)还原速率;碱性水稻土中潜在fe(iii)还原菌在淹水初期受ph调节抑制后,于淹水5d-20d相对丰度升高,对应于淹水初期受抑制的fe(iii)还原过程和淹水中后期显著的fe(ii)累积。(6)通过对不同水稻土水溶性有机碳三维荧光光谱扫描鉴定发现4个共有的类腐殖酸荧光组分,其来源以外源输入为主,内源输入为辅。水溶性有机碳的腐殖化系数与Fe(Ⅲ)还原特征参数存在显著的相关关系。其中以陆源的大分子量UVC类腐殖酸对Fe(Ⅲ)还原特征的贡献最高,陆源的UVC+UVA类腐殖酸和海源的UVA海洋腐殖酸与Fe(Ⅲ)还原特征参数的相关关系也达到显著或极显著水平,而水溶性有机碳含量的贡献最小。推测水稻土中水溶性有机碳的腐殖化程度及其中各类腐殖酸组分的含量与水稻土Fe(Ⅲ)还原能力正相关。(7)生物炭添加可以促进水稻土中微生物Fe(Ⅲ)还原能力,且促进作用随着生物炭粒度减小而逐渐增强。究其原因,一方面生物炭的水溶性有机碳作为电子穿梭体加速了Fe(Ⅲ)还原过程;另一方面生物炭的添加促进了游离氧化铁和硝态氮含量对Fe(Ⅲ)还原过程的贡献。采用葡萄糖修饰生物炭不仅可以促进水稻土中氧化铁的还原过程,也可以缓减生物炭的“碱性基团”引起的pH升高,且生物炭粒度越小作用越显著。通过本文的研究,对水稻土中微生物Fe(Ⅲ)还原过程相关的环境条件和Fe(Ⅲ)还原微生物的群落结构与功能有了更深入的认识,探讨了水稻土淹水过程中微生物发酵有机质对Fe(Ⅲ)还原具有重要贡献,使水稻土中Fe(Ⅲ)的兼性共代谢还原机理及其贡献被重视,为进一步揭示淹水稻田中Fe(Ⅲ)还原的机理及提高有机污染物的降解提供理论依据。
[Abstract]:The process of iron reduction in paddy field and paddy soil carbon, nitrogen, sulfur, phosphorus and other elements geochemical cycle is closely related to Fe (III) reduction process at the same time the oxidative coupling of the degradation of organic pollutants and heavy metals price reduction process, which significantly inhibited the production of methane in paddy field, so the study of paddy field in Fe (III) reduction process and its mechanism has important geochemical and environmental significance. Earlier on Fe (III) reduction process of cognition mainly concentrated in the sediment environment, a large number of studies have confirmed that the reduction process of iron oxide is the alienation of sediments such as anaerobic environment Fe (III) the main way to restore, and co metabolism the reduction process and often anaerobic organic matter decomposition phase coupling, known as Fe (III) secondary reduction pathway. However with sediment in long-term anaerobic environment, formed by the oxidation of paddy upland rotation tillage mode The microbial metabolic reduction environment alternately, organic hydrogen production process has become an important link in the chain of electron transfer. The paddy field in microbial fermentation of organic matter and co metabolism mechanism of the reduction of iron oxide remains to be further in-depth. This research adopts Heng Wenpei anaerobic cultivation methods, typical paddy soils of different planting in our collection, comparison the different soil physicochemical properties of Fe and (III) reduction of the different characteristics, reveal the effect of paddy field in Fe (III) the main factors of the reduction process; by adding different organic carbon source and adjusting soil pH conditions, microbial community structure of organic matter in the process of anaerobic fermentation, dehydrogenation and hydrogen production process Fe (III) the relationship between the reduction process, production of small molecular organic carbon, microbial fermentation process of hydrogen production, acid production of Fe (III) reduction process; by fluorescence excitation. Study on the spectral scanning shoot different paddy soil water fluorescence characteristic of dissolved organic carbon and the main components, reveal the dissolved organic matter and Fe (III) reduction process; biological carbon as the carrier, the use of the characteristics of its high content of aromatic structure and strong adsorption ability, using low molecular weight organic carbon modified biochar, on the promotion of Fe in paddy soils (III) reduction process of the potential, and water soluble organic carbon electron transfer function and microbial fermentation of organic compounds on Fe (III) by reduction of the contribution of this theory to practice. The main results are as follows: (1) in paddy soil after Fe, (II) with the flooding time and the gradual accumulation of different rice soil between Fe (III) there were significant differences in the reduction characteristics. The physicochemical properties of soil, organic matter content and the content of amorphous iron oxides of Fe (III) is the main factor reducing characteristics, both of the two With Fe (III) reduction potential of a and Fe (III) reduction rate of Vmax had a significant positive correlation, and pH is the maximum Fe (III) the main factors of time required for the reduction rate. (2) in paddy soil Fe (III) response regulation of different carbon reduction process because of the different soil vary greatly. The soil microbial pH using glucose induced decrease in the acid paddy soil Fe (III) reduction process. The use of microorganisms in paddy soils of different carbon substrates for fermentation hydrogen production process of dehydrogenation occurred mainly in the initial stage of culture, the hydrogen producing ability from strong to weak glucose pyruvate and lactate dehydrogenase activity, corresponding to the maximum time of microbial iron (III) and Fe reaction time reached the maximum reaction rate (TVmax) is consistent with the training system of pH decreased. It showed that the production of H+ microbial fermentation is the main source of organic carbon To product, Fe (OH) 3 as electron acceptor was consumed by microbial reduction process using different types of carbon source fermentation culture system of h2. pH and H2 and the partial pressure of Fe (II) accumulation had significant negative correlation, indicating that microbial utilization of organic carbon source fermentation to produce organic acid, then influence dehydrogenation of hydrogen production characteristics and effects on the microbial Fe (III) reduction process. (3) can be used as nutrients and iron receptor consumption, flooding microbial communities in paddy soil and potential Fe (III) reduction bacteria showed significant succession. Firmicutes is the most dominant species, with prolonged flooding the relative abundance decreased; acidobacteria, Bacteroidetes, Chloroflexi, Proteobacteria and ignavibacteriae are second kinds of advantages, relative abundance were gradually increased with the flooding time prolonged. Exogenous addition of different concentration of glucose for microbial extract For the abundant carbon source, the microbial community succession lags behind, so that a large number of Firmicutes enrichment, especially with hydrogen fermentation function of Clostridium and bacillus, and the hysteresis effect by increasing the carbon source concentration increased. Different concentrations of glucose to Bacillus and Clostridium enrichment water, formation of paddy soil in Desulfitobacterium, solibacillus, potential Fe anaeromyxobacter and Paenibacillus (III) by reducing bacteria. With addition of different concentrations of glucose when microbial dehydrogenation characteristics of hydrogen production and Fe (III) reduction characteristics, verify the different concentrations of glucose regulated Fe (III) potential reducing bacteria community structure and the dehydrogenation process of hydrogen production of Bacillus and Clostridium in response to changes in community structure the interaction effect of Fe (III) reduction process. (4) the initial pH regulation of paddy soil microbial activity in the dehydrogenation of hydrogen production, the corresponding enzyme activity and Fe (III) Change of solubility and further influence on Fe (III) reduction process. When the regulation of acidic and alkaline paddy soil initial pH Xeon acid or acidic, dehydrogenase activity during incubation was significantly inhibited, which inhibited the acidic paddy soil in alkaline paddy soil can promote the hydrogen production process. Although in this case the acid soluble Fe (III) concentrations were not conditioning significantly increased, but Fe (III) reduction process is still inhibited by lowering the initial pH, so the solubility is not under the condition of low pH iron oxide is Fe (III) reduction process. The main factors regulating paddy soil initial pH to neutral and alkaline. Strong alkaline, dehydrogenation and Fe microorganisms (III) solubility is regulated by pH, the alkaline soil is adjusted to neutral and acidic paddy soil was adjusted to neutral, alkaline and alkaline hydrogen partial pressure decreased significantly, the Fe (III) reduction. Before reaching the maximum reaction rate of Fe (III), reflecting the use and consumption of the hydrogen reduction process. In different initial pH paddy soil Fe (III) during the period of rapid reduction, can with Fe dehydrogenase activity characterization of microbial metabolism of organic matter (II) accumulation is closely related. (5) microbial hydrogen production in paddy soil the dehydrogenation process of soil organic matter fermentation and potential Fe (III) reduction response regulating bacterial community structure on the initial pH directly or indirectly affect the Fe in paddy soil (III) reduction process. When the regulation of acid paddy soil to alkaline after bacterial community structure by adjusting the pH effect and waterlogging affected by initial Firmicutes pH regulates the relative abundance increased. The proportion of Proteobacteria accounted for the alkaline bacteria in paddy soil with initial pH adjusted to acid increased, the bacterial community structure by regulating pH and there is a big difference. The potential of Fe in acid paddy soil (III) reducing bacteria abundance Is not the adjustment increase, corresponding to the increase of Fe (III) Fe to H2 reduction in advance consumption and achieve reduction rate (III); potential Fe alkaline paddy soil (III) reducing bacteria is regulated by the pH inhibition of waterlogging, flooding in the relative abundance of 5d-20d increased, corresponding to waterlogging inhibition of Fe (III) Fe post process and significant reduction in cumulative flooding (II). (6) dissolved organic carbon by scanning and identification of three-dimensional fluorescence spectra of different paddy soil water found 4 common humic like fluorescence components, its main source with exogenous input, the input of endogenous water-soluble supplement. The humification coefficient of organic carbon and Fe (III) there is a significant correlation between the reduction parameters. With large molecular weight UVC terrestrial humic acid on Fe (III) reduction characteristics of the contribution of the highest class UVC+UVA terrestrial humic acid and marine UVA marine humic acid and Fe (III) reduction characteristic parameters Correlation between the number has reached a significant level, while the water soluble organic carbon content. The minimum contribution that paddy soil water soluble organic carbon humification degree and including all kinds of humic acid composition and the content of Fe in paddy soils (III) reduction ability is related. (7) biochar can add promotion of microbial Fe in paddy soil (III) reduction ability, and the effect increases with biochar particle size. The reason for a biological carbon water soluble organic carbon as an electron shuttle acceleration of Fe (III) reduction process; on the other hand, biochar promoted free iron oxide and nitrate the nitrogen content of Fe (III) reduction process. The modified biochar with glucose can not only promote the reduction process of iron oxides in paddy soil, can also reduce the biochar "alkaline group" caused by the increase of pH, and the smaller the particle size effect of biochar more . through this study, the microbial Fe in paddy soil (III) reduction process related to the environmental conditions and Fe (III) to restore the structure and function of microorganisms have more in-depth understanding, discusses the flooded paddy soils in microbial fermentation of organic matter to Fe (III) reduction has an important contribution to rice the soil Fe (III) and co metabolism reduction mechanism and its contribution is emphasized, in order to further reveal the paddy field in Fe (III) provides a theoretical basis for the reduction of the mechanism and improve the degradation of organic pollutants.

【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ920.1;S154.3
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本文编号：1407033