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Modeling the role of highly oxidized multifunctional organic molecules for the growth of new particles over the boreal forest region

Öström, Emilie LU ; Putian, Zhou; Schurgers, Guy LU ; Mishurov, Mikhail LU ; Kivekäs, Niku LU ; Lihavainen, Heikki; Ehn, Mikael; Rissanen, Matti P.; Kurtén, Theo and Boy, Michael, et al. (2017) In Atmospheric Chemistry and Physics 17(14). p.8887-8901
Abstract

In this study, the processes behind observed new particle formation (NPF) events and subsequent organic-dominated particle growth at the Pallas Atmosphere-Ecosystem Supersite in Northern Finland are explored with the one-dimensional column trajectory model ADCHEM. The modeled sub-micron particle mass is up to ∼75 % composed of SOA formed from highly oxidized multifunctional organic molecules (HOMs) with low or extremely low volatility. In the model the newly formed particles with an initial diameter of 1.5 nm reach a diameter of 7 nm about 2 h earlier than what is typically observed at the station. This is an indication that the model tends to overestimate the initial particle growth. In contrast, the modeled particle growth to CCN size... (More)

In this study, the processes behind observed new particle formation (NPF) events and subsequent organic-dominated particle growth at the Pallas Atmosphere-Ecosystem Supersite in Northern Finland are explored with the one-dimensional column trajectory model ADCHEM. The modeled sub-micron particle mass is up to ∼75 % composed of SOA formed from highly oxidized multifunctional organic molecules (HOMs) with low or extremely low volatility. In the model the newly formed particles with an initial diameter of 1.5 nm reach a diameter of 7 nm about 2 h earlier than what is typically observed at the station. This is an indication that the model tends to overestimate the initial particle growth. In contrast, the modeled particle growth to CCN size ranges (> 50 nm in diameter) seems to be underestimated because the increase in the concentration of particles above 50 nm in diameter typically occurs several hours later compared to the observations. Due to the high fraction of HOMs in the modeled particles, the oxygen-to-carbon (O : C) atomic ratio of the SOA is nearly 1. This unusually high O : C and the discrepancy between the modeled and observed particle growth might be explained by the fact that the model does not consider any particle-phase reactions involving semi-volatile organic compounds with relatively low O : C. In the model simulations where condensation of low-volatility and extremely low-volatility HOMs explain most of the SOA formation, the phase state of the SOA (assumed either liquid or amorphous solid) has an insignificant impact on the evolution of the particle number size distributions. However, the modeled particle growth rates are sensitive to the method used to estimate the vapor pressures of the HOMs. Future studies should evaluate how heterogeneous reactions involving semi-volatility HOMs and other less-oxidized organic compounds can influence the SOA composition- and size-dependent particle growth.

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Atmospheric Chemistry and Physics
volume
17
issue
14
pages
15 pages
publisher
Copernicus Gesellschaft Mbh
external identifiers
  • scopus:85025810704
  • wos:000406152600001
ISSN
1680-7316
DOI
10.5194/acp-17-8887-2017
language
English
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yes
id
91f002b0-1d75-483d-8ba5-13ae4e0e9a83
date added to LUP
2017-08-02 09:19:28
date last changed
2017-09-18 11:40:45
@article{91f002b0-1d75-483d-8ba5-13ae4e0e9a83,
  abstract     = {<p>In this study, the processes behind observed new particle formation (NPF) events and subsequent organic-dominated particle growth at the Pallas Atmosphere-Ecosystem Supersite in Northern Finland are explored with the one-dimensional column trajectory model ADCHEM. The modeled sub-micron particle mass is up to ∼75 % composed of SOA formed from highly oxidized multifunctional organic molecules (HOMs) with low or extremely low volatility. In the model the newly formed particles with an initial diameter of 1.5 nm reach a diameter of 7 nm about 2 h earlier than what is typically observed at the station. This is an indication that the model tends to overestimate the initial particle growth. In contrast, the modeled particle growth to CCN size ranges (&gt; 50 nm in diameter) seems to be underestimated because the increase in the concentration of particles above 50 nm in diameter typically occurs several hours later compared to the observations. Due to the high fraction of HOMs in the modeled particles, the oxygen-to-carbon (O : C) atomic ratio of the SOA is nearly 1. This unusually high O : C and the discrepancy between the modeled and observed particle growth might be explained by the fact that the model does not consider any particle-phase reactions involving semi-volatile organic compounds with relatively low O : C. In the model simulations where condensation of low-volatility and extremely low-volatility HOMs explain most of the SOA formation, the phase state of the SOA (assumed either liquid or amorphous solid) has an insignificant impact on the evolution of the particle number size distributions. However, the modeled particle growth rates are sensitive to the method used to estimate the vapor pressures of the HOMs. Future studies should evaluate how heterogeneous reactions involving semi-volatility HOMs and other less-oxidized organic compounds can influence the SOA composition- and size-dependent particle growth.</p>},
  author       = {Öström, Emilie and Putian, Zhou and Schurgers, Guy and Mishurov, Mikhail and Kivekäs, Niku and Lihavainen, Heikki and Ehn, Mikael and Rissanen, Matti P. and Kurtén, Theo and Boy, Michael and Swietlicki, Erik and Roldin, Pontus},
  issn         = {1680-7316},
  language     = {eng},
  month        = {07},
  number       = {14},
  pages        = {8887--8901},
  publisher    = {Copernicus Gesellschaft Mbh},
  series       = {Atmospheric Chemistry and Physics},
  title        = {Modeling the role of highly oxidized multifunctional organic molecules for the growth of new particles over the boreal forest region},
  url          = {http://dx.doi.org/10.5194/acp-17-8887-2017},
  volume       = {17},
  year         = {2017},
}