Preprints
https://doi.org/10.5194/acp-2020-128
https://doi.org/10.5194/acp-2020-128

  22 Apr 2020

22 Apr 2020

Status: this preprint has been withdrawn by the authors.

The trend of the oxidants in boreal forest over 2007–2018: comprehensive modelling study with long-term measurements at SMEAR II, Finland

Dean Chen1, Putian Zhou1,2, Tuomo Nieminen1,3, Pontus Roldin4, Ximeng Qi5, Petri Clusius1, Carlton Xavier1, Lukas Pichelstorfer1, Markku Kulmala1,5, Pekka Rantala1, Juho Aalto1, Nina Sarnela1, Pasi Kolari1, Petri Keronen1, Matti P. Rissanen6, Metin Baykara1,2, and Michael Boy1,2 Dean Chen et al.
  • 1Institute for Atmospheric and Earth Systems Research/Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
  • 2Climate and Marine Sciences Department, Eurasia Institute of Earth Sciences, Istanbul Technical University, Maslak 34469, Istanbul, Turkey
  • 3Institute for Atmospheric and Earth Systems Research/Forest Sciences, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
  • 4Division of Nuclear Physics, Department of Physics, Lund University, P.O. Box 118, 221 00 Lund, Sweden
  • 5Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, 210023, China
  • 6Aerosol Physics Laboratory, Physics Unit, Faculty of Engineering and Natural Sciences, Tampere University, Tampere, Finland

Abstract. Major atmospheric oxidants (OH, O3 and NO3) dominate the atmospheric oxidation capacity, while H2SO4 is considered as a main driver for new particle formation events. Although numerous studies have investigated the long-term trend of ozone in Europe, the trend of OH, NO3 and H2SO4 at specific sites are to a large extent unknown. In this study, we investigated how the trends in major atmospheric oxidants (OH, O3 and NO3) and H2SO4 changed in southern Finland during the past 12 years and discuss how these trends relate to decreasing emissions of regulated air pollutants in Europe. The one-dimensional model SOSAA has been applied in several studies at the SMEAR II station, and has been validated by measurements in several projects. Here, we ran the SOSAA model for the years 2007–2018 to simulate the atmospheric chemical components, especially the atmospheric oxidants and H2SO4 at SMEAR II. The simulations were evaluated with observations at SMEAR II for several shorter and longer campaigns. Our results show that OH increased by +1.56 (−0.8; +3.17) % yr−1 during daytime and NO3 decreased by −3.92 (−6.49; −1.79) % yr−1 during nighttime, indicating different trends of the oxidants during day and night. Sulphuric acid decreased during daytime by −5.12 (−11.39; −0.52) % yr−1, which correlated with the observed decreasing concentration of newly formed particles in the size range 3–25 nm by 1.4 % yr−1 at SMEAR II during the years 1997–2012 (Nieminen et al., 2014). Additionally we compared our simulated OH, NO3 and H2SO4 concentrations with proxies, which are commonly applied in case limited amount of parameters are measured and no detailed model simulations are available.

This preprint has been withdrawn.

Dean Chen et al.

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Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Dean Chen et al.

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This preprint has been withdrawn.

Short summary
Atmospheric oxidants OH, O3 and NO3 dominate the atmospheric oxidation capacity, and sulfuric acid (H2SO4) is considered as a main driver for new particle formation events. We studied how the trends of these atmospheric oxidants and H2SO4 changed in southern Finland during the past 12 years and discussed how these trends related to decreasing emissions of air pollutants in Europe. Our results showed that OH increased by 1.56 % yr−1 at daytime and NO3 decreased by 3.92 % yr−1 at nighttime.
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