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Contributions of biogenic volatile organic compounds to the formation of secondary organic aerosols over Mt. Tai,Central East China
Authors:Pingqing Fu  Kimitaka Kawamura  Yugo Kanaya  Zifa Wang
Institution:1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi''an 710061, China;2. Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 200041, China;3. Center of Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China;4. University of Chinese Academy of Sciences, Beijing 100049, China;5. State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
Abstract:To better understand the contribution of biogenic volatile organic compounds to the formation of secondary organic aerosol (SOA) in high mountain regions, ambient aerosols were collected at the summit of Mt. Tai (1534 m, a.s.l.), Central East China (CEC) during the Mount Tai Experiment 2006 campaign (MTX2006) in early summer. Biogenic SOA tracers for the oxidation of isoprene, α/β-pinene, and β-caryophyllene were measured using gas chromatography/mass spectrometry. Most of the biogenic SOA tracers did not show clear diurnal variations, suggesting that they are formed during long-range atmospheric transport or over relatively long time scales. Although isoprene- and α/β-pinene-derived SOA tracers did not correlate with levoglucosan (a biomass burning tracer), β-caryophyllinic acid showed a good correlation with levoglucosan, indicating that crop residue burning may be a source for this acid. Total concentrations of isoprene oxidation products are much higher than those of α/β-pinene and β-caryophyllene oxidation products. The averaged ratio of isoprene to α/β-pinene oxidation products (Riso/pine) was 4.9 and 6.7 for the daytime and nighttime samples, respectively. These values are among the highest in the aerosols reported in different geographical regions, which may be due to the large isoprene fluxes and relatively high levels of oxidants such as OH in CEC. Using a tracer-based method, we estimated the concentrations of secondary organic carbon (SOC) derived from isoprene, α/β-pinene, and β-caryophyllene to be 0.42–3.1 μgC m?3 (average 1.6 μgC m?3) during the daytime and 0.11–4.2 μgC m?3 (1.7 μgC m?3) during the nighttime. These values correspond to 2.9–23% (10%) and 3.2–28% (9.8%) of the total OC concentrations, in which isoprene-derived SOC accounts for 58% and 63% of total SOC during the daytime and nighttime, respectively. This study suggests that isoprene is a more significant precursor for biogenic SOA than α/β-pinene and β-caryophyllene at high altitudes in CEC.
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