科研之友
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摘要
Biomass combustion (BC) is an important source of humic-like substances (HULIS) in atmospheric aerosol, and the oxidation process has a significant impact on the optical properties and chemical structures of BC-HULIS. This study focused on the changes in primary BB-HULIS due to ozone (O3) oxidation and the optical properties and chemical structure of HULIS before and after oxidation were characterized with the total organic carbon (TOC) analyzer, UV-Vis spectroscopy, Excitation-Emission Matrix coupled with parallel factor analysis (EEM-PARAFAC) and Fourier transform infrared spectroscopy (FTIR). The results showed that the relative contents of HULIS in the corresponding water-soluble organic carbon (WSOC) decreased with O3 oxidation, suggesting the transformation of HULIS into water-soluble low molecular weight compounds. Furthermore, mass absorption efficiency (MAE365) and aromatic index (SUVA254) of HULIS decreased from 1.8~2.7m2/gC and 4.2~5.0m2/gC to 1.1~1.3m2/gC and 3.7~4.1m2/gC, respectively, indicating that both the absorption capacity and aromaticity of HULIS declined with O3 oxidation. The fluorescent components in BC-HULIS were mainly composed of protein-like compounds (C2) and humic-like substances (C1, C3, C4). After O3 oxidation, the total fluorescence intensities of BC-HULIS weakened greatly, and the relative contribution of two types of fluorophores and fluorescence index were all significantly changed. For instances, the relative contents of humic-like components and the humidification index (HIX) of BC-HULIS after O3 oxidation were obviously higher than those before O3 oxidation, suggesting the degradation of protein-like compounds and the aggregation of humic-like substances during the O3 oxidation process. In addition, FTIR results showed that the oxygen-containing functional groups were markedly enhanced after O3 oxidation, indicating effects of O3 oxidation on the chemical functional groups of BC-HULIS.
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单位中国科学院; 有机地球化学国家重点实验室
