示差红外光谱在土壤有机质组成研究中的应用

Studies on Composition of Soil Organic Matter by Fourier Transform Infrared Spectroscopy Differential Analysis

采用红外透射光谱法,对不同管理方式下黑土有机质组成进行了红外光谱分析,并运用差谱的方法,降低土壤矿物对有机吸收峰的干扰。选择2920、2850、1630和1420 cm^(-1)作为代表有机质官能团的吸收峰,通过积分计算各吸收峰的相对面积,并对吸收峰面积与土壤有机质(SOM)的组分含量进行了相关分析。土壤在2920 cm^(-1)处脂族结构的吸收峰面积与土壤活性有机碳(水溶性有机碳、热水溶性有机碳、游离态轻组碳和闭蓄态轻组碳)含量呈正相关,可反映土壤活性有机碳含量;在1630 cm^(-1)处芳香结构的吸收峰面积与以上活性有机碳含量呈负相关,可反映土壤稳定性有机碳含量。土壤在1630和2920 cm^(-1)处吸收峰面积的比值(1630∶2920)与稳定性(重组)有机碳和活性(轻组)有机碳含量的比值呈显著正相关,可指示SOM的稳定程度。本方法所需样品量少、成本低、便捷,适用于对矿物组成一致的土壤进行有机质组成的测定。

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-1 were 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-1 in 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-1 in the bulk soil suggested a relationship with more stable SOM compounds.The ratio of the peaks at 1630 and 2920 cm-1 was 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.