Characterization of Soil Humic Substances Using Mid-infrared Photoacousctic Spectroscopy

摘要

Fourier Transfrom Infrared photoacoustic spectra (FTIR-PAS) have been applied to characterize soil humic substances,i.e.,humic acid (HA),mobile humic acid (MHA) and recalcitrant calcium humate (CaHA) from Loenardite soil.Conventional transmittance infrared spectra and FTIR-PAS spectra of these humic substances were collected.The FTIR-PAS spectra were significantly different from the transmittance spectra.Totally,the absorption bands of transmittance spectra in the wavenumber range of 2,000-3,800 cm-1 were significantly broader than that of FTIR-PAS spectra,but the absorption bands in the in the wavenumber range of 1,000-1,800 cm-1 were obviously narrow that that of FTIR-PAS spectra.The band height of both aliphatic and carboxyl groups in the FTIR-PAS spectra were lower than that in transmittace spectra,however,the ratios of these two band were similar,and the ratio can be used to show the capability of water repellence of humic substances.All the results indicated that FTIR-PAS technique could provide a simple and fast method for quantifying of functional groups in soil humic substances.