Detection of dissolved organic matter in saline–alkali soils using synchronous fluorescence spectroscopy and principal component analysis

Abstract Dissolved organic matter (DOM) is attributed a key role in soil major biogeochemical processes. Its molecular characteristics can reflect both its source and its biogeochemical history. Saline–alkali soil samples were collected from a field in desert and semi-desert region. DOM was analyzed by synchronous fluorescence spectroscopy. Principal Components Analysis (PCA) of synchronous fluorescence spectra was used to detect and describe changes in the DOM in different soil profiles. The analysis of PCA yielded 2 PCs that account for 97% of the variance. DOM is characterized by a dominant tyrosine-like fluorophore in the Region I (PC1 > 0.9, PC2  0.9) and lower PC1 ( I 345/318 and I 362/318 .) can be used to indicate the humification of DOM. The humification degree of the remaining soils has no systematic trend because of land use, agricultural irrigation, soil erosion and salinization. Soils obtained a relatively high humification degree in the region II and a relatively low humification degree in the region I.