Single particle mass spectrometry of oxalic acid in ambient aerosols in Shanghai: Mixing state and formation mechanism |
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| Authors: | Fan Yang Hong Chen Xinning Wang Xin Yang Jianfei Du Jianmin Chen |
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| Institution: | 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;1. Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433,;2. State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China;3. Key Laboratory of Marine Environment and Ecology, Ministry of Education, Ocean University of China, Qingdao 266100, China |
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| Abstract: | Oxalic acid in individual aerosol particles was measured using single particle aerosol time-of-flight mass spectrometry (ATOFMS) in the summer of 2007 in Shanghai, China. Oxalate was found in 3.4% of total particles with diameters in the range of 0.2 – 2.0 μm. Size, chemical composition and hourly temporal counts of single particles that contained oxalic acid were measured. The predominant types of oxalate-containing particles were characterized to distinguish the primary and secondary sources of oxalic acid. Biomass burning was revealed as a major primary source of oxalic acid which contributed more than 20% of the oxalate-containing particles. Evidences for two different formation pathways of oxalic acid were observed in our experiment. The number fraction of oxalate-containing particles correlated with that of sulfate particles and the changes of air parcel backward trajectories, suggesting that in-cloud processing played important roles in oxalic acid formation. The diurnal patterns of dust and sea salt particle counts fitted well with the ambient relative humidity variation, suggesting that heterogeneous reactions occurring in hydrated/deliquesced aerosols also contributed to the production of oxalic acid. |
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