PM_(2.5)中水溶性有机物吸光特性的模拟研究

Simulation study of light absorption characteristics of water-soluble organic matter in PM_(2.5)

研究建立了超声雾化器与光声光谱仪,扫描电迁移率颗粒物粒径谱仪联用的分析系统,将深圳市2011年夏季采集的PM2.5膜样品提取液雾化发生气溶胶,使之进入光声光谱仪检测其吸光强度以研究气溶胶中水溶性有机物(WSOM)的吸光特征.结果表明:观测期间PM2.5中WSOM平均质量浓度为(4.3±2.3)μg/m3,分别占PM2.5和OM质量浓度的11.9%±4.8%和49.2%±18.5%.WSOM在405,532,781nm波长下的质量吸收效率值(MAE)分别为(0.55±0.31),(0.54±0.31),(0.21±0.13)m2/g.经计算所得:深圳市夏季大气PM2.5中WSOM在405,532,781nm波长下的平均吸收系数分别为(2.30±1.08),(2.25±1.26),(0.86±0.45)Mm-1,对应的WSOM对大气PM2.5整体吸光效应的贡献率分别为7.6%,10.6%和5.8%,说明WSOM对PM2.5整体吸光效应的贡献不容忽视,有机气溶胶在大气灰霾中的能见度损害作用值得进一步深入研究.

This study established an experimental system that combined an ultrasonic nebulizer with a photo-acoustic soot spectrometer and a scanning mobility particle sizer for measuring light absorption of water-soluble organic matter （WSOM） in PM2.5. PM2.5 samples were collected in the summer of 2011 in Shenzhen, and aerosols were re-generated from the water extracts using the ultrasonic nebulizer. The light absorption of the aerosols was then detected by the photo-acoustic soot spectrometer. The results show that the average mass concentration of WSOM during the campaign was （4.3±2.3） μg/m3, accounting for 11.9%±4.8% of PM2.5 and 49.2%±18.5% of OM, respectively. The Mass Absorption Efficiency （MAE） of WSOM at the wavelengths of 405, 532 and 781nm was （0.55±0.31）, （0.54±0.31） and （0.21±0.13） m^2/g, respectively. Further calculations show that the light absorption of WSOM at the wavelengths of 405, 532and 781nm was （2.30±1.08）, （2.25±1.26） and （0.86±0.45） Mm^-1, respectively, which contributed 7.6%, 10.6% and 5.8% to the entire PM2.5 light absorption at the corresponding wavelengths, respectively. The contribution of WSOM to aerosol light absorption is potentially important and more studies on the role of organic aerosol in visibility deterioration should be carried out.