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.
Atmospheric oxidants OH, O3 and NO3 dominate the atmospheric oxidation capacity, and sulfuric...
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
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
Received: 13 Feb 2020 – Accepted for review: 07 Apr 2020 – Discussion started: 22 Apr 2020
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.
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.
Atmospheric oxidants OH, O3 and NO3 dominate the atmospheric oxidation capacity, and sulfuric...