Parameterization of Thermal Properties of Aging Secondary Organic Aerosol Produced by Photo-Oxidation of Selected Terpene Mixtures
详细信息 查看全文
- 作者：Eva U. Emanuelsson ; Thomas F. Mentel ; 脜got K. Watne ; Christian Spindler ; Birger Bohn ; Theo Brauers ; Hans-Peter Dorn ; 脜sa M. Hallquist ; Rolf H盲seler ; Astrid Kiendler-Scharr ; Klaus-Peter M眉ller ; H氓kan Pleijel ; Franz Rohrer ; Florian Rubach ; Eric Schlosser ; Ralf Tillmann ; Mattias Hallquist
- 刊名：Environmental Science & Technology
- 出版年：2014
- 出版时间：June 3, 2014
- 年：2014
- 卷：48
- 期：11
- 页码：6168-6176
- 全文大小：381K
- 年卷期：v.48,no.11(June 3, 2014)
- ISSN：1520-5851
文摘
Formation and evolution of secondary organic aerosols (SOA) from biogenic VOCs influences the Earth鈥檚 radiative balance. We have examined the photo-oxidation and aging of boreal terpene mixtures in the SAPHIR simulation chamber. Changes in thermal properties and chemical composition, deduced from mass spectrometric measurements, were providing information on the aging of biogenic SOA produced under ambient solar conditions. Effects of precursor mixture, concentration, and photochemical oxidation levels (OH exposure) were evaluated. OH exposure was found to be the major driver in the long term photochemical transformations, i.e., reaction times of several hours up to days, of SOA and its thermal properties, whereas the initial concentrations and terpenoid mixtures had only minor influence. The volatility distributions were parametrized using a sigmoidal function to determine TVFR0.5 (the temperature yielding a 50% particle volume fraction remaining) and the steepness of the volatility distribution. TVFR0.5 increased by 0.3 卤 0.1% (ca. 1 K), while the steepness increased by 0.9 卤 0.3% per hour of 1 脳 106 cm鈥? OH exposure. Thus, aging reduces volatility and increases homogeneity of the vapor pressure distribution, presumably because highly volatile fractions become increasingly susceptible to gas phase oxidation, while less volatile fractions are less reactive with gas phase OH.