生物质燃烧排放颗粒物中水溶性有机物的光学特性

Optical properties of water-soluble organic matters in particulate matter from biomass burning

采用紫外-可见光吸收光谱法(UV-vis)和激发-发射矩阵荧光光谱法(EEM)分析了典型生物质燃烧排放颗粒物(PM_(2.5))中水溶性有机物(WSOM)的光学特性.结果表明,WSOM的SUVA_(254)、E_(250)/E_(365)和MAE_(365)值分别为1.79—2.60 m^(2)·g^(−1)、4.56—7.65和0.66—1.17 m^(2)·g^(−1),说明生物质燃烧排放PM_(2.5)中WSOM具有较低的芳香度和分子量以及较弱的吸光能力.荧光光谱结果显示,WSOM产生荧光峰的主要范围为λ_(Ex)/λ_(Em)≈(230—250)/(335—380)nm和λ_(Ex)/λ_(Em)≈(260—290)/(330—360)nm,说明生物质燃烧排放PM_(2.5)中WSOM主要以类蛋白荧光物质为主;腐殖化指数(HIX)、荧光指数(FI)和自生源指数(BIX)分别为0.49—1.09、2.03—2.68和1.32—1.81,说明生物质燃烧排放PM_(2.5)中WSOM的腐殖化程度、芳香性和分子量均较低.相关性分析结果显示,生物质燃烧排放PM_(2.5)中WSOM的MAE_(365)值与SUVA_(254)和HIX值呈显著正相关关系,与E_(250)/E_(365)和BIX呈显著负相关性,说明生物质燃烧排放PM_(2.5)中WSOM的光吸收特性与芳香性、腐殖化程度和自生源贡献有着紧密的联系.

The optical properties of water-soluble organic matters(WSOM)in particulate matter(PM_(2.5))from biomass burning were analyzed by ultraviolet-visible absorption spectroscopy(UV-Vis)and excitation-emission matrix fluorescence spectroscopy(EEM).The results showed that the SUVA_(254),E_(250)/E_(365) and MAE_(365 )values of WSOM were 1.79—2.60 m^(2)·g^(−1),4.56—7.65 and 0.66—1.17 m^(2)·g^(−1),respectively,indicating that the WSOM in PM_(2.5) emitted from biomass burning exhibited low aromaticity and molecular weight as well as weak light absorption capacity.EEM results showed that the main wavelength ranges of fluorescence peaks generated by WSOM wereλ_(Ex)/λ_(Em)≈(230—250)/(335—380)nm andλ_(Ex)/λ_(Em)≈(260—290)/(330—360)nm,implying that the protein-like substances were dominant fluorophores for WSOM in PM_(2.5) emitted from biomass burning.Humification index(HIX),fluorescence index(FI)and freshness index(BIX)were 0.49—1.09,2.03—2.68 and 1.32—1.81,respectively,suggesting that WSOM in PM_(2.5) emitted from biomass burning had low humification degree,aromaticity and molecular weight.Correlation analysis showed that MAE_(365) value of WSOM in PM_(2.5) emitted from biomass burning was significantly positively correlated with SUVA_(254) and HIX,but negatively with E_(250)/E_(365) and BIX,indicating that the light absorption characteristics of WSOM emitted from biomass burning were closely related to their aromaticity,humification degree and autochthonous.