复合污染旱田黄土中还田秸秆动态腐解的光谱学特性

秸秆是农业生产的重要副产物，其资源化再利用一直是国内外学者关注的热点。目前，秸秆还田已成为秸秆资源化利用的主要途径之一。还田秸秆能在合适的土壤环境和土壤微生物的作用下腐烂分解，将腐殖质和矿质元素等组分释放进入土壤体系。这不仅能改变土壤固有的肥力属性，对于土壤重金属污染物的环境化学行为也将产生一定影响。实验土壤采集于西部典型黄土区，采用SEM-EDS、元素分析、FTIR和13C NMR等光谱联用技术，研究复合污染黄土中还田秸秆腐解残体的表面特性及生成胡敏酸性质差异。实验结果表明：在秸秆还田全程，秸秆腐解残体呈现出“结构致密→表面崩解→骨架破坏”的表面形貌动态变化特性，EDS检测结果揭示了腐解残体元素组成的变化行为。新生成的胡敏酸脂族性较高、芳香性较低，属于较“新鲜”和“年轻”的胡敏酸，有利于提高黄土有机质活性。秸秆腐解各阶段FTIR图谱具有很高的相似性，波峰的变化揭示了胡敏酸生成过程的复杂性。13C NMR结果说明胡敏酸芳香性逐渐降低、脂族性不断增加，证实了胡敏酸分子结构的简单化趋势。光谱联用技术对于揭示黄土区秸秆还田过程胡敏酸的性质差异是可行的。

Spectral Characteristics of Decomposition of Incorporated Straw in Compound Polluted Arid Loess

The original loess from western China was used as soil sample, the spectral methods of scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), elemental analysis, Fourier transform infrared spectroscopy (FT-IR) and 13C nuclear magnetic resonance (13C NMR) were used to investigate the characteristics of decomposed straw and formed humic acids in compound polluted arid loess. The SEM micrographs show the variation from dense to decomposed surface, and finally to damaged structure, and the EDS data reveal the phenomenon of element transfer. The newly-formed humic acids are of low aromaticity, helpful for increasing the activity of organic matters in loess. The FTIR spectra in the whole process are similar, indicating the complexity of transformation dynamics of humic acids. The molecular structure of humic acids becomes simpler, shown from 13C NMR spectra. The spectral methods are useful for humic acids identification in loess region in straw incorporation process.