中文摘要：

以西北旱田黄土为研究对象,分析玉米秸秆还田前后黄土可溶性有机质（DOM）的三维荧光光谱差异,探讨黄土腐殖化程度的变化情况及对Pb（Ⅱ）赋存形态的影响。实验结果表明：黄土DOM的荧光峰主要分布在λex/em=240～270/280～340区域和λex/em=325/450附近,分别归属为紫外区类富里酸以及可见光区类富里酸和腐殖酸类物质的荧光峰。秸秆还田60d后,紫外区类富里酸荧光峰值增加,在λex/em=250/440附近和λex/em=320～350/350～400区域出现新的腐殖酸荧光峰。黄土腐殖化程度随秸秆还田时间的延长而增加,Pb（Ⅱ）的生物有效性随腐殖化程度的增加而降低。三维荧光光谱可以有效表征秸秆还田前后黄土DOM的变化特性。

英文摘要：

The three-dimensional fluorescence spectrum was used to investigate the fluorescence characterization of dissolved or- ganic matter （DOM） before and after straw incorporation in arid loess, and the variation of humification degree and Pb（ II ） spe- ciation were illustrated. The results showed that the fluorescence peaks of loess appears at the regions of λex/em =240--270/280- 340 and λex/em = 325/450, referred as UV fulvic-like fluorescence, and visible fulvie-like and humic-like fluorescence, respective- ly. After straw incorporation for 60 days, the intensity of UV fulvic-like fluorescence peaks increases, and novel humic-like fluo- rescence peaks appears around the region of λex/e, =250/440 andλex/em----320-350/350-400. The longer time of straw incorpo- ration would accelerate the humification degree of loess and decrease the bioactivity of Pb（ II ）. The three-dimensional fluores- cence spectrum is appropriate for characterization identification of DOM in arid loess before and after straw incorporation.