秸秆还田是秸秆资源化和减量化的主要途径之一, 是国家“十二五”期间的重要政策导向。 还田秸秆能够发生天然腐殖化, 逐步完成溶解性有机质(DOM)的生成和转化过程。 现阶段, 针对黄土地区环境因子对秸秆腐殖化调控作用的研究较少, 从荧光光谱角度分析腐殖化组分与金属离子的结合特性也有待完善。 以荧光光谱法为切入点, 探讨温度和铅离子对秸秆腐殖化DOM三维荧光光谱峰位和峰强的影响, 借助修正型Stern-Volmer方程推算Pb(Ⅱ)-DOM的配位参数, 辅以Van’t Hoff方程揭示结合过程的热力学特性。 结果表明: 腐殖化温度没有引起DOM荧光峰位的明显偏移, 三维荧光光谱中没有发现新荧光峰的出现或已有荧光峰的消失, 荧光峰强随温度的升高而降低。 铅离子浓度的增加导致DOM主要荧光峰强下降, 这是铅离子对DOM组分的荧光猝灭作用。 经修正型Stern-Volmer方程计算可知: 铅离子对可见光区类富里酸组分的配位能力最强, 较大的配位荧光基团比例f值暗示DOM中较多的活性基团与铅离子发生配位作用, 猝灭机理以静态猝灭为主。 配位过程自发、 吸热, 反应体系分子组成的复杂性和无序度较低。 三维荧光光谱能够有效揭示温度和铅离子对秸秆腐殖化DOM性质的影响。

Straw incorporation is significant for straw reduction and reutilization, and is clearly required in the twelfth five-year-plan for national economic and social development of the People’s Republic of China. The incorporated straw will naturally decompose and release the component of dissolved organic matter (DOM). At present, it lacks the research on straw humification behavior controlled by environmental factors and complexation effect between humification component and metal ions with fluorescence spectrometry in the representative region of loess. The fluorescence spectrometry was used to reveal the 3D-EEMs characteristics of DOM affected by temperatures and lead ions in the straw humification process, and the modified Stern-Volmer equation and Van’t Hoff equation were applied to indicate the complexation parameters and thermodynamic constants between lead ions and DOM. The results showed: the humification temperatures affected little on fluorescence peaks of DOM and no peaks were obviously found to appear or disappear from the 3D-EEMs results. The fluorescence intensity decreased gradually at higher temperatures and in the presence of lead ions, the quenching effect might work in the process. The binding ability was more significant between lead ions and visible fulvic-like component shown from modified Stern-Volmer equation, and the values of f revealed the complexation effect of lead ions and functional groups in DOM. Static quenching was the primary mechanism during the reaction process. The constants in Van’t Hoff equation suggested the reaction was spontaneous and endothermic, and the disordered degree and the complexity were relatively low in the reaction system. The 3D-EEMs were acceptable to illustrate the variation of DOM characteristics under different temperatures and in the presence of lead ions in the straw humification process.