燃烧生成棕色碳的三维荧光光谱分析

Comparisons of three-dimensional fluorescence spectra of brown carbon from combustion

模拟燃烧11种常见物质(秸杆、木材、煤和生活垃圾等),并收集烟气中可溶于甲醇的有机产物,利用紫外-可见吸收光谱(UV-Vis)和三维荧光光谱(EEMs)对收集的甲醇可溶性有机物(MSOM)进行表征.进一步,结合非负矩阵分解法(NMF)提取三维荧光光谱主要组分的特征激发/发射光谱,根据荧光信号轮廓差异对不同种类物质进行区分,旨在建立棕色碳溯源依据.结果显示,秸杆和木材燃烧源棕色碳在紫外-可见吸收光谱上呈现相似的谱形,均在265nm处存在肩峰;瓦楞纸板和塑料燃烧源棕色碳的吸收则随波长增加单一下降.由于基本组分相同,各生物质及纸板对应的棕色碳的EEM有着相似的轮廓,NMF解析结果表明,生物质和纸板的MSOM存在3种主要荧光组分,分别为两种类腐殖质C1、C2和类蛋白质C3;煤的EEM在长波处有较强的分布,可归因于芳香类基团,由其EEM分解出M1、M2和M3荧光团,三者位置均较生物质红移.根据荧光团位置以及光谱信号轮廓特征,可对生物质和煤进行区分;泡沫、塑料袋和塑料瓶属于有机高分子材料,其EEM与生物质有较大的差别,且三者之间也存在差异,泡沫和塑料袋的MSOM含有4种荧光成分,而从塑料瓶的MSOM中只可得到两种荧光团,特征明显.

11 common substances,including straw,wood,coal,waste paper and waste plastics,were employed to simulate combustion in the laboratory and the methanol soluble organic matters(MSOM)in smoke were collected.The brown carbon in MSOM was characterized by UV-Vis and three-dimensional fluorescence spectroscopy(EEMs).Furthermore,non-negative matrix decomposition(NMF)was used to extract the characteristic excitation/emission spectra of main components of EEM,aiming to establish the basis of brown carbon traceability.The results show that the UV-vis spectra of straw and wood burning source brown carbon were similar with a shoulder peak at 265nm.The absorption of brown carbon from corrugated board and plastic combustion sources decreases singly with increasing wavelength.Due to the same basic components,the EEM of brown carbon corresponding to biomass and paperboard had similar profiles.NMF analysis showed three main fluorescent components in MSOM of biomass and paperboard,which were two humus C1,C2 and protein-like C3,respectively.The EEM of coal has a strong distribution in the long wave,which can be attributed to aromatic groups.From its EEM,the M1,M2 and M3 fluorophores can be decomposed and their positions are redshifted compared to those of biomass.According to fluorophore position and spectral signal profile,biomass and coal can be distinguished.Foam,plastic bag and plastic bottle are organic polymer materials and their EEM is quite different from that of biomass.The MSOM of foam and plastic bag contains four fluorescent components,while the MSOM of plastic bottle can only get two fluorophore groups with obvious characteristics.