近边X射线吸收精细结构光谱法研究土壤腐殖质组分含碳官能团组成及磷酸根影响

Study on C-Functional Groups of Soil Humus Fractions Affected by Phosphate Using C 1s Near-edge X-ray Absorption Fine Structure Spectroscopy

应用同步辐射近边X射线吸收精细结构(NEXAFS)光谱技术研究了土壤腐殖质各组分(富里酸、胡敏酸及胡敏素等)的含碳官能团组成信息,并通过分析PO43-存在条件下胡敏酸、胡敏素的官能团组成变化特征,探讨了PO43-与土壤腐殖质之间的微观作用机制。结果表明,土壤腐殖质不同组分的官能团分布具有类似的光谱特征,但组成比例存在明显差异。随着腐殖质组分的酸不溶性增加,胡敏酸、胡敏素疏水性脂肪基官能团比例显著高于富里酸,芳构化程度也明显增加,而亲水性羧基官能团比例趋于降低;PO43-通过静电作用、取代反应可以选择性释放胡敏酸中部分小分子羧基官能团,从而改变胡敏酸官能团的组成特征。此研究结果对于应用NEXAFS研究有机碳官能团形态、结构及理解PO43-在土壤微界面上的反应机制具有重要意义。

Synchrotron based near-edge X-ray absorption fine structure（NEXAFS） spectroscopy was applied to study the C-functional group chemistry of various soil humus fractions（including fulvic acid,humic acid and humin） and to explore the reaction mechanisms between phosphate and humus.The results indicated that the humus fractions contained similar functional groups but at different proportions.Humic acid and humin,with the increasing acid-insolubility,exhibited higher content of hydrophobic functional groups and higher aromaticity while lower carboxylic C when compared with fulvic acid.The presence of phosphate could favor the release of the hydrophilic carboxylic functional groups into soil solutions through substitution reactions as well as electrostatic effects,and thus exert significant effects on the functional group chemistry of soil humic substances.The results will be great helpful to study the speciation and composition of C-functional groups with NEXAFS spectroscopy and to understand the reaction mechanisms of phosphate in soil micro-interfaces.