在污染场地植物修复过程中, 植物根系通过释放活性分泌物主动适应和抵御污染胁迫, 直 (间) 接影响根际圈土壤DOM的结构组成。 现阶段, 植物修复的关注点主要集中于污染物的吸收、 转运、 累积和解毒行为, 对于根际圈土壤DOM的探讨略显不足。 以Pb/Cd复合污染黄土区金盏菊幼苗为研究对象, 分析根际圈黄土Pb/Cd赋存形态、 金盏菊生长状况等宏观差异, 借助紫外可见光谱(UV)、 傅里叶变换红外光谱(FTIR)和三维荧光光谱(3D-EEMs)明确Pb/Cd胁迫前后根际圈黄土DOM的微观性质。 结果表明: 根际圈黄土Pb/Cd以残渣态和可交换态为主, 金盏菊生长周期结束后可交换态Pb/Cd含量有所升高。 Pb/Cd胁迫抑制了金盏菊株高和出苗率, 其生长周期有助于改善黄土理化性质。 胁迫后金盏菊根部呈现细长、 弯曲且萎缩的迹象; DOM紫外光谱最大吸收区间位于200～240 nm, 但胁迫后的图谱波峰更加尖锐, 峰强更大。 Pb/Cd胁迫导致DOM红外吸收峰分别从3 444和1 637 cm-1移动至3 440和1 645 cm-1, 其中存在重金属离子与OH和CO结合效应。 DOM荧光峰集中在λex/em=240/430附近(紫外区类富里酸荧光峰), Pb/Cd胁迫对荧光峰强干扰较大, 而对荧光峰位基本没有影响。 金盏菊根际圈黄土DOM能够提供重要的微生态环境信息, 光谱学手段能够一定程度上揭示其与Pb/Cd赋存形态的构效关系。

The various characteristics of DOM have great impact on the transformation process of contaminants in soil due to the generation of the feedback regulation in cycles of plant, Rhizosphere soil and environmental contaminants. Currently, more attention was paid on contaminants behaviors of adsorption, transformation, accumulation and detoxification than DOM derived from Rhizosphere soil. The chemical speciation of lead/cadmium and growth efficiency related variations were revealed in the growth process of Calendula officinalis seedlings, and the spectral characteristics of DOM in Rhizosphere loess were discussed with UV, FT-IR and 3D-EEMs spectra. The results showed: the dominant contents of lead/cadmium are in residual and exchangeable speciation, and the exchangeable contents increase greatly after the growth of Calendula officinalis seedlings. It causes negative effects on the height and emergency rate of Calendula officinalis seedlings with lead/cadmium, and the Calendula officinalis is able to positively improve loess characteristics. The root of Calendula officinalis appears to be longer, thinner and flexuous. The maximum absorption band of DOM in UV spectra locates in 200~240 nm, and the sharper and greater intensity of peaks can be detected under lead/cadmium stress. The absorption peaks in FT-IR spectra move from 3 444 and 1 637 to 3 440 and 1 645 cm-1, respectively, indicating the combination effects between metal ions and functional groups of—OH and CO. The dominant fluorescence peaks of DOM are found to be aroundλex/em=240/430, described as fulvic-acid like components, and metals in loess affect more on peaks intensity than locations. The characteristics of DOM in Rhizosphere loess of Calendula officinalis seedlings contain much micro-eco-environmental information, and the spectral approaches are efficient to reveal the relationship between DOM and chemical speciation of lead/cadmium.