九宫山垂直带土壤有机质矿化特征及其稳定性机制

发布时间：2018-07-05 02:29

本文选题：土壤有机质 + 矿化　；参考：《华中农业大学》2016年博士论文

【摘要】：土壤有机质作为最大的陆地碳库,与土壤肥力、全球碳循环等密切相关,其稳定性对于土壤生态系统抵抗外界环境变化具有重要意义。有机质可与土壤中其它组分相互作用,其稳定性受各种生物及非生物因素的制约。本研究采集九宫山不同海拔土壤,通过分子荧光光谱、碳库分级等技术,分析土壤培养前后有机组分性质和矿化特征。同时借助元素分析、傅里叶红外光谱(FTIR)、核磁共振波谱(NMR)等技术分析不同土壤中胡敏酸(HA)的结构特征;通过粒径分级、X射线衍射(XRD)及红外光谱等手段,研究了影响土壤有机质稳定性的物理、化学及生物学机制。基于上述结果,合成了复合铁铝氧化物,并纯化培养了革兰氏阴性和阳性细菌,通过不同反应条件下HA吸附实验、ζ电位测试、红外光谱等技术,研究了铁铝氧化物吸附HA的微观机制,初步探讨了铁氧化物、细菌及其复合体的HA吸附特性,得到如下主要结论:1)随海拔降低,生物活性碳库有机碳(SOC)含量降低,有机碳矿化总量及速率减小。同时,随土壤深度增加,WEOC平均分子量增加,腐殖化程度和芳香缩合度增加,分子结构趋于复杂,导致深层土壤中SOC矿化率明显低于表层。供试土壤矿化前后惰性氮在全氮中的比例(RN)均随土壤深度增加而增加,但惰性碳在有机碳中的比例(RC)随深度变化不明显。RN与SOC矿化呈显著负相关(P0.05),但RC与SOC矿化的相关性不显著,深层土壤中氮的有效性对有机质矿化比碳有效性更为重要。SOC矿化总量取决于有机质数量,但其矿化率主要取决于有机组分的生物有效性。土壤经短期矿化培养后,WEOC平均分子量和共轭结构减少,芳化度和腐殖化程度降低,分子结构趋于简单。2)九宫山不同海拔土壤中HA含量及结构特征差异显著。随海拔增加,HA总量及相对含量均增加,且酸性土壤中HA易于在土壤表层富集。供试HA主要来源于植物残体,也含有微生物代谢物质;其结构中以烷基碳(25-40%)和烷氧碳(21-44%)为主,1500 m处二者含量相当,1200 m处烷基碳较多,600 m处烷氧碳较多。随海拔上升,HA芳化度增加;随土壤深度增加,HA芳化度显著降低。HA腐殖化程度为1500 m处最高,600 m处最低,与有机碳矿化总量的变化一致。此外,HA分子的芳香缩合度、结构复杂度及其疏水性随海拔的变化均为1200 m1500 m600 m,与SOC矿化率变化相反。3)600和1500 m处矿物稳定有机碳(MOC)含量主要与有机碳形态和铁氧化物有关,1200 m处铝氧化物促进了MOC的积累。铁铝氧化物比层状矿物对有机质的保护能力更强,且非晶质矿物比晶质矿物的影响更大。铁氧化物比铝氧化物对有机质稳定性的影响弱。土壤有机碳主要存在于微团聚体;酚类、多糖及芳香类物质易在小颗粒中积累,而烷烃、醇类物质在大颗粒土壤中含量相对丰富。大团聚体对易氧化碳的保护能力强于微团聚体,但后者对芳香物质的保护更显著。芳香类物质通过与矿物结合增强其稳定性;烷烃、酚类及多糖的稳定受其结构的影响更大。矿物稳定有机碳是土壤稳定有机碳的重要组成,HA也是稳定有机组分的物质来源。土壤有机质稳定性可通过与矿物结合成有机-矿物复合体、团聚体的空间位阻效应及有机质自身结构的稳定三种方式实现。4)复合铁铝氢氧化物与HA的相互作用受矿物表面性质、溶液pH及离子强度的影响。pH 5.0时,HA最大吸附量为FeAl,在复合Fe-Al氧化物中其吸附量随Fe含量增加而增加;HA吸附亲和力随Al含量增加而增大;酸性条件下,铝氧化物的配位能力强于铁氧化物。铁铝氧化物优先吸附HA中芳香组分,且与Fe相比,Al吸附态HA的芳香度较高。HA分子中羧基、酚羟基及脂肪碳均参与吸附反应,且Fe比Al更易与氨基结合。随溶液离子强度增加,各矿物的HA吸附量均增加;纯矿物中HA吸附量为AlFe,复合Fe-Al氧化物的HA吸附量与Al含量成反比。随体系pH增加HA吸附量降低,除Al的吸附亲和力与pH变化趋势相反,其余各矿物的吸附亲和力在pH 7.0时最大,pH 5.0时最小。高pH条件下铁铝氧化物优先吸附HA中脂肪族物质。5)水铁矿的HA吸附量高于赤铁矿,枯草芽孢杆菌的HA吸附量高于恶臭假单胞菌。铁氧化物与细菌共存抑制对HA吸附,且水铁矿-细菌复合体的HA吸附抑制率高于赤铁矿-细菌复合体,恶臭假单胞菌-氧化物复合体的HA吸附抑制率高于枯草芽孢杆菌-氧化物复合体。低浓度磷酸盐抑制铁氧化物及铁氧化物-细菌复合体对HA的吸附,高浓度磷酸盐对复合体中HA吸附的抑制率降低,甚至促进HA吸附。本研究分析了团聚、吸附及有机质结构特征对有机质稳定性的相对贡献,可为自然环境中土壤有机质的转化与积累研究提供理论参考。
[Abstract]:As the largest terrestrial carbon pool, soil organic matter is closely related to soil fertility and global carbon cycle. Its stability is of great significance to soil ecosystem resistance to the change of the external environment. Organic matter can interact with other components in the soil, and its stability is restricted by various biological and abiotic factors. At different altitudes, the characteristics of the unit and mineralization of soil were analyzed by molecular fluorescence spectrum and carbon pool classification. At the same time, the structure characteristics of Hu Min acid (HA) in different soils were analyzed by elemental analysis, Fourier infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR), and X ray diffraction (XRD) by particle size classification. The physical, chemical and biological mechanisms affecting the stability of soil organic matter were studied by means of infrared spectroscopy. Based on the above results, the composite iron and aluminum oxides were synthesized and the Gram-negative and positive bacteria were purified and cultured. The iron and aluminum oxides were studied by HA adsorption experiments under different reaction conditions, Zeta potential test and infrared spectroscopy. The adsorption properties of HA were preliminarily discussed. The HA adsorption characteristics of iron oxides, bacteria and their complexes were preliminarily discussed. 1) the contents of organic carbon (SOC) decreased with the decrease of altitude, and the total amount and rate of organic carbon mineralization decreased. At the same time, the average molecular weight of WEOC increased with the increase of soil depth, the degree of humification and aromatic contraction. The percentage of SOC mineralization in deep soil was obviously lower than that in surface layer. The proportion of inert nitrogen in total nitrogen (RN) increased with soil depth before and after mineralization, but the proportion of inert carbon in organic carbon (RC) had no significant negative correlation with SOC mineralization with the depth of.RN (P0.05), but RC and SOC The correlation of mineralization is not significant. The availability of nitrogen in deep soil is more important for the mineralization of organic matter than carbon. The total amount of.SOC mineralization depends on the quantity of organic matter, but the mineralization rate depends mainly on the bioavailability of the organic matter. After the short-term mineralization of the soil, the average fraction of WEOC and the conjugated structure of the soil are reduced, the degree of aromatization and humification of the soil are reduced. The content and structural characteristics of HA in the soils of different altitudes of the nine palace mountains were significantly different. The total and relative content of HA increased with the elevation of the altitude, and the HA in the acid soil was easy to be enriched in the soil surface. The experimental HA was mainly derived from the plant residues and also contained microbial metabolites; in its structure, the structure of alkyl carbon (25-4) 0%) and alkoxy carbon (21-44%), the content of two people at 1500 m is equal, 1200 m is more alkyl carbon and more alkoxy carbon at 600 m. With the increase of altitude, the degree of HA aromatization is increased; the degree of HA aromatization is the highest with the depth of soil increasing, the degree of.HA humification is highest, 600 m is the lowest, and the change of organic carbon mineralization is the same. In addition, HA molecule aromatic The variation of aroma and shrinkage, structure complexity and its hydrophobicity are 1200 m1500 M600 m with the elevation of altitude, which is opposite to SOC mineralization rate.3. The content of mineral stable organic carbon (MOC) at 600 and 1500 m is mainly related to organic carbon morphology and iron oxide, and aluminum oxide at 1200 m promotes the accumulation of MOC. The soil organic carbon is mainly in the micro aggregates; the phenols, polysaccharides and aromatic substances are easily accumulated in the small particles, and the alkanes and alcohols are relatively rich in the large granular soil. Large aggregate aggregates. The protection of oxidizable carbon is stronger than that of the micro aggregate, but the latter is more significant for the protection of aromatic substances. The stability of aromatics is enhanced by combining with minerals; the stability of alkanes, phenols and polysaccharides is more affected by its structure. Mineral stable organic carbon is an important component of soil stable organic carbon, and HA is also a stable unit. The stability of soil organic matter can be stabilized by combining with minerals into organic mineral complex, the spatial hindrance effect of the aggregate and the stability of the organic matter's self structure in the three ways of.4) the interaction of the compound iron aluminum hydroxide with HA is affected by the mineral surface properties. The maximum adsorption capacity of HA is Fe when the solution pH and the intensity of the ionization of the HA are.PH 5. The adsorption capacity of Al increased with the increase of Fe content in the compound Fe-Al oxide, and the adsorption affinity of HA increased with the increase of Al content. Under the acid condition, the coordination ability of aluminum oxide was stronger than that of the iron oxide. The iron and aluminum oxides first adsorbed the aromatic component of HA, and the aromatic degree of Al adsorbed HA was higher than that of the Fe, and the carboxyl group, phenol hydroxyl group and lipid in.HA molecules were higher than that of Fe. The fatty carbon all participates in the adsorption reaction, and Fe is more easily bound to the amino group than the Al. With the increase of the ionic strength of the solution, the HA adsorption amount of each mineral increases; the adsorption amount of HA in the pure mineral is AlFe, the HA adsorption amount of the compound Fe-Al oxide is inversely proportional to the Al content. With the pH increase of the HA, the adsorption capacity of HA decreases, except the Al adsorption affinity is the opposite to pH variation trend. The adsorption affinity of minerals is maximum at pH 7 and minimum at pH 5. Under high pH conditions, iron and aluminum oxides first adsorb aliphatic.5 in HA). The adsorption amount of HA in pyrite is higher than that of hematite, and the HA adsorption capacity of Bacillus subtilis is higher than that of Pseudomonas stinsii. The coexistence of iron oxides and bacteria to HA adsorption, and HA of the pyrite bacterial complex The inhibition rate of adsorption was higher than that of hematite bacterial complex, and the inhibition rate of HA adsorption in Pseudomonas aeruginosa complex complex was higher than that of Bacillus subtilis oxide complex. Low concentration phosphate inhibited the adsorption of iron oxide and iron oxide bacterial complex on HA, and the inhibition rate of HA adsorption in the complex of high concentration phosphate decreased and even promoted. This study analyzed the relative contribution of aggregation, adsorption and organic matter structure characteristics to the stability of organic matter, which could provide a theoretical reference for the study of the transformation and accumulation of soil organic matter in natural environment.
【学位授予单位】：华中农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S153.6

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