北京森林土壤富里酸亚组分的表征及荧光指标分析

为探究土壤FA（富里酸）的结构组成及其腐殖化和芳香性特征，采用SFS（同步荧光光谱）技术结合FRI（荧光区域积分）、DSFS（导数荧光光谱）及PCA（主成分分析）对土壤FA亚组分的荧光光谱特征及荧光指标间的相关性进行了分析.利用XAD-8吸附树脂结合初始pH为3、5、7、9和13的Na₄P₂O₇（焦磷酸钠）缓冲溶液逐步洗脱技术将土壤FA分别分级得5种亚组分（FA₃、FA₅、FA₇、FA₉和FA₁₃）.结果表明:①FA₃-FA₁₃的SFS体现3类荧光峰，分别代表类蛋白、类富里酸和类腐殖酸物质.FA₃和FA₅含有含量相近的类蛋白、类富里酸和类腐殖酸物质，而FA₇-FA₁₃含有的主要成分是类蛋白物质；同时，FA₇-FA₁₃的类富里酸和类腐殖酸较FA₃和FA₅更为复杂，且FA₇-FA₁₃含有更多易降解的单环芳香族化合物.②FA₃和FA₅的类酪氨酸和类色氨酸物质被识别，且FA₇-FA₁₃的类色氨酸含量明显大于类富里酸和类腐殖酸含量.③FA₃-FA₁₃光谱荧光强度指标（I₂₄₀/I₃₄₀、I₂₄₀/I₄₅₀、I₃₄₀/I₂₇₀、I₄₅₀/I₂₇₀和I₄₅₀/I₃₄₀）的对比分析表明，FA₃和FA₅的腐殖化程度和芳香性均大于FA₇-FA₁₃.④荧光指标A_FLR/A、A_HLR/A、S_270-340、S_270-450、A₂/A₁和A₃/A₁可作为指示亚组分芳香性的优化指标，且A_HLR/A、A₂/A₁和A₃/A₁可作为最佳指标反映亚组分的腐殖化程度.研究显示，土壤FA亚组分的结构表征及荧光指标分析为后续FA亚组分与环境污染物相互机理研究提供依据，为探究有机质的结构特性和环境行为提供理论支撑. 

Characterization and Fluorescence Index Analysis for Forest Soil Fulvic Acid Sub-Fractions in Beijing

In order to explore the structures and compositions, and the characteristics of humification and aromaticity of soil fulvic acid (FA), the synchronous fluorescence spectra (SFS) technique combined with fluorescence region integral (FRI) method, derivative synchronous fluorescence spectra (DSFS) method and principal component analysis (PCA) were utilized to study the spectral characteristics and the correlations among fluorescence indexes for FA sub-fractions. The XAD-8 adsorption technique coupled with the stepwise elution using Na₄P₂O₇ buffers with initial pH values 3, 5, 7, 9 and 13 were used to separate the FA into five sub-fractions:FA₃, FA₅, FA₇, FA₉ and FA₁₃, respectively. The results indicated that three fluorescence peaks were shown in the SFS of FA₃-FA₁₃, which represented the protein-like, fulvic-like and humic-like materials, respectively. FA₃ and FA₅ contained similar content of protein-like, fulvic-like and humic-like materials, while protein-like materials were the primary components in FA₇-FA₁₃. Meanwhile, FA₇-FA₁₃ contained more complex structures in fulvic-like and humic-like materials than those in FA₃ and FA₅, and FA₇-FA₁₃ had more biodegradable monocyclic aromatic compounds. Tyrosine-like and tryptophan-like materials in FA₃-FA₅ were identified by DSFS method. Additionally, the content of tryptophan-like materials in FA₇-FA₁₃ was significantly higher than that of both fulvic-like and humic-like materials. The comparative analysis of fluorescence intensity indexes (I₂₄₀/I₃₄₀, I₂₄₀/I₄₅₀, I₃₄₀/I₂₇₀, I₄₅₀/I₂₇₀ and I₄₅₀/I₃₄₀) for FA₃-FA₁₃ indicated that FA₃ and FA₅ had higher humidification degree and aromaticity than FA₇-FA₁₃. Further, the A_FLR/A, A_HLR/A, S_270-340, S_270-450, A₂/A₁ and A₃/A₁ could be optimized indexes for indicating the aromaticity of FA sub-fractions, and A_HLR/A, A₂/A₁ and A₃/A₁ were the best indexes for reflecting their humidification degree. The study shows that the characterization and fluorescence index analysis of soil FA sub-fractions could provide the basis for the future interaction studies between FA sub-fractions and environmental pollutants and the theoretical supports for exploring the structural properties and environmental behaviors of dissolved organic matter.