不同种植年限苏打盐碱型水稻土水溶性有机物三维荧光光谱特征分析

【目的】揭示不同种植年限苏打盐碱型水稻土水溶性有机物(WEOM)的变化规律,为苏打盐碱型水稻土固定有机碳提供理论基础。【方法】利用三维荧光光谱技术研究种植水稻0、1、3、5、15和20年对苏打盐碱地土壤中WEOM含量(w)及其三维荧光特性的影响。【结果】随种植年限的延长,土壤WEOM的含量先增加后逐渐降低,在种植3年时达最大(259.29 mg·kg-1),而在20年时最小(19.29 mg·kg-1);土壤中WEOM D254 nm随种植年限增加而增加;WEOM的三维荧光图谱形状和荧光线密度不同,荧光线密度随种植年限的增加而增强;随种植年限增加,水稻土中区域Ⅰ和区域Ⅱ的荧光峰的发射光波长发生了蓝移,而区域Ⅲ和区域Ⅴ发射光波长发生了红移;土壤积分值为区域Ⅴ区域Ⅲ区域Ⅳ区域Ⅱ区域Ⅰ;种植20年后,类腐殖物质占WEOM的百分比降低。【结论】苏打盐碱型水稻土中类富里酸、类腐殖物质以及含有不饱和双键的芳香族化合物含量随种植年限而增加。三维荧光技术适用于研究土壤中WEOM的结构和组分。

Three-dimensional fluorescence spectral characteristics of water extractable organic matter in soda saline-alkaline paddy soil with different planting years of rice

Objective] To investigate the changing patterns of water extractable organic matter ( WEOM) in soda saline-alkaline paddy soil in the fields with different planting years of rice, and provide a theoretical basis for increasing organic carbon fixation in such soil. [Method] Three-dimensional fluorescent spectroscopy was performed to study the contents and fluorescence characteristics of WEOM in soda saline-alkaline paddy soil with 0, 1, 3, 5, 15 and 20 planting years of rice. [Result] With the increase of planting age, the content of WEOM in soil first increased and then decreased, reached the maximum ( 259. 29 mg · kg-1 ) after planting rice for three years, and was the lowest ( 19. 29 mg·kg-1 ) after planting rice for 20 years. The absorbance of WEOM at UV 254 nm increased with planting age. The shape of the three-dimensional fluorescence spectra of WEOM was different from fluorescence linear density which increased with planting age. There was a blue shift in the emission wavelength of the fluorescence peak in region I and region II of paddy soil, and a red shift in region Ⅲand region Ⅴ. The fluorescence regional integration values were region Ⅴ> region Ⅲ> region Ⅳ>region Ⅱ> regionⅠ. The proportion of humic acid-like substance in WEOM was reduced after planting rice for 20 years. [Conclusion] The humic substances, fulvic acid-like substance and unsaturated aromatic compounds in soda saline-alkaline paddy soil increase with planting age. Three-dimensional fluorescence technique can be applied to study the structure and composition of WEOM in soil.