An examination of oxidant amounts on secondary organic aerosol formation and aging |
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| Authors: | Zhong Chen Omar Torres |
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| Institution: | 1. Mass Spectrometry in Reactive Flows – Thermodynamics, IVG, University of Duisburg-Essen, D-47048 Duisburg, Germany;2. Molecular Dynamics Group, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland\n;3. Institute of Combustion Technology, German Aerospace Center (DLR), Pfaffenwaldring 38-40, D-70569 Stuttgart, Germany;1. Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi''an 710061, China;2. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi''an 710061, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;4. Department of Environmental Science, Xi''an Jiaotong University, Xi''an 710049, China |
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| Abstract: | The effect of HOx radicals (OH and HO2) and ozone (O3) on aerosol formation and aging has been studied. Experiments were performed in presence as well as in absence of oxygen in a flow-through chamber at 299 K for three organic precursor gases, isoprene, α-pinene and m-xylene. The HOx source was the UV photolysis of humidified air or nitrogen and was measured with a GTHOS (Ground-based Tropospheric Hydrogen Oxides Sensor). The precursor gases concentration was monitored with an online GC-FID. The aerosol mass was then quantified by a Tapered Element Oscillating Microbalance (TEOM). Typical oxidant mixing ratios were (0–4.5) ppm for O3, 200 pptv for OH and 3 ppbv for HO2. A simple kinetics model is used to infer the aerosol production mechanism. In the present of O3 (or O2), the SOA yields were 0.46, 0.036 and 0.12 for α-pinene with an initial concentration of 100 ppbv (RH = 37%), isoprene with an initial concentration of 177 ppbv (RH = 50%) and m-xylene with an initial concentration of 100 ppbv (RH = 37%), respectively. When the chosen precursor gases reacted with HOx in the absence of O3, the maximum SOA yields were significantly increased by factors of 1.6 for isoprene 1.1 for α-pinene, and 3 for m-xylene respectively. The comparison of the calculated and measured potential aerosol mass concentrations as function of time shows that presence of ozone or oxygen can influence the aerosol yield and the absence of ozone or oxygen in the system resulted in high concentrations of its organic aerosol products. |
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