Missing ozone-induced potential aerosol formation in a suburban deciduous forest

Publication date: Available online 10 October 2017
Source:Atmospheric Environment
Author(s): T. Nakayama, Y. Kuruma, Y. Matsumi, Y. Morino, K. Sato, H. Tsurumaru, S. Ramasamy, Y. Sakamoto, S. Kato, Y. Miyazaki, T. Mochizuki, K. Kawamura, Y. Sadanaga, Y. Nakashima, K. Matsuda, Y. Kajii
As a new approach to investigating formation processes of secondary organic aerosol (SOA) in the atmosphere, ozone-induced potential aerosol formation was measured in summer at a suburban forest site surrounded by deciduous trees, near Tokyo, Japan. After passage through a reactor containing high concentrations of ozone, increases in total particle volume (average of 1.4 × 10⁹ nm³/cm³, which corresponds to 17% that of pre-existing particles) were observed, especially during daytime. The observed aerosol formations were compared with the results of box model simulations using simultaneously measured concentrations of gaseous and particulate species. According to the model, the relative contributions of isoprene, monoterpene, and aromatic hydrocarbon oxidation to SOA formation in the reactor were 24, 21, and 55%, respectively. However, the model could explain, on average, only ∼40% of the observed particle formation, and large discrepancies between the observations and model were found, especially around noon and in the afternoon when the concentrations of isoprene and oxygenated volatile organic compounds were high. The results suggest a significant contribution of missing (unaccounted-for) SOA formation processes from identified and/or unidentified volatile organic compounds, especially those emitted during daytime. Further efforts should be made to explore and parameterize this missing SOA formation to assist in the improvement of atmospheric chemistry and climate models.

Graphical abstract

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