Studies on Composition of Soil Organic Matter by Fourier Transform Infrared Spectroscopy Differential Analysis / 分析化学

ABSTRACT

Fourier transform mid-infrared spectroscopy (FTIR) method was used to analyze the soil organic matter (SOM) composition of a black soil under different management types. Spectral subtraction method was used for eliminating the interference of soil mineral to the absorption peak. Peaks at 2920,2850,1630 and 1420 cm-1were selected as a range of organic functional groups, and relative areas of these peaks were calculated by integral method. The correlation between peak areas and the content of SOM fractions were analyzed. Positive correlations between carbon (C) in fractions representing labile SOM (water-soluble organic carbon,hot water-soluble organic carbon, free light fraction carbon, occluded light fraction carbon) and the peak area at 2920 cm-1in the bulk soil indicated that this aliphatic peak corresponded to the more labile C compounds. Negative correlations between the same fractions and the area of the predominantly aromatic peak at 1630 cm-1in the bulk soil suggested a relationship with more stable SOM compounds. The ratio of the peaks at 1630 and 2920 cm-1was positively correlated with the ratio of stable C(heavy fraction) to labile C (light fraction) and thus taken as an indicator of SOM stability. This method was convenient, low cost and less sample usage,and could be used to analyze the organic carbon composition of soils which has the same mineral composition.