Sources, sinks and transformation of BVOCs and aerosols in boreal forest boundary layer

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dc.contributor Helsingin yliopisto, matemaattis-luonnontieteellinen tiedekunta, fysiikan laitos fi
dc.contributor Helsingfors universitet, matematisk-naturvetenskapliga fakulteten, institutionen för fysik sv
dc.contributor University of Helsinki, Faculty of Science, Department of Physics en
dc.contributor.author Zhou, Putian fi
dc.date.accessioned 2018-04-13T07:16:47Z
dc.date.available 2018-04-10 fi
dc.date.available 2018-04-13T07:16:47Z
dc.date.issued 2018-04-20 fi
dc.identifier.uri URN:ISBN:978-952-7276-02-0 fi
dc.identifier.uri http://hdl.handle.net/10138/234205
dc.description.abstract A large amount of biogenic volatile organic compounds (BVOCs) are emitted from boreal forests. Once emitted, BVOCs can be oxidized in the air, participate in particle formation and growth and thus indirectly affect local, regional and global climate. BVOCs act as a bridge between the biosphere and the atmosphere including atmospheric chemistry in both gas and particle phases. In this thesis we studied the in-canopy sources and sinks of BVOCs, the roles of BVOCs in gas and particle phases, as well as the impact of aerosol dynamics on the vertical aerosol fluxes in the planetary boundary layer. Several findings in this thesis are shown below: (1) By using a newly implemented gas dry deposition model in a one-dimensional chemical transport model SOSAA (model to Simulate the concentrations of Organic vapours, Sulphuric Acid and Aerosols) we simulated the in-canopy source and sink terms of 12 featured BVOCs. According to the strength of individual terms, BVOCs were classified into five categories: Cemis in which most of the emitted gases are transported out of the canopy, Cemis-chem in which most of the emitted gases are quickly oxidized inside the canopy, Cemis-depo in which emissions are comparable to deposition, Cdepo in which the dominant deposition sink leads to downward fluxes and Cchem-depo in which the chemical production compensates a part of deposition. (2) High upward fluxes of formic acid over a boreal forest were observed. The required unknown precursors and emission sources were quantified to explain the missing sources inside the canopy. (3) The simulated O3 concentration change due to chemical reactions related to BVOCs was in average less than 10% of the deposition sink. (4) The highly oxidized multifunctional organic molecules (HOMs) play a dominant role in the growth of new particles over the sub-Arctic forest region at the Pallas Atmosphere-Ecosystem Supersite and account for ∼ 75% of total SOA mass during new particle formation events. (5) The modelled vertical aerosol fluxes above the canopy caused by aerosol dynamics were comparable or sometimes exceeded that caused by particle dry deposition. This introduced large biases between measured flux and the particle dry deposition flux. The findings (1), (2), (3), (5) were obtained over the boreal forest at SMEAR (Station for Measuring ecosystem-Atmosphere Relations) II. This thesis provides a new numerical tool to analyse detailed sources and sinks of BVOCs, which can be applied in other ecosystems and further implemented in large-scale models. en
dc.description.abstract A large amount of biogenic volatile organic compounds (BVOCs) are emitted from boreal forests. Once emitted, BVOCs can be oxidized in the air, participate in particle formation and growth and thus indirectly affect local, regional and global climate. BVOCs act as a bridge between the biosphere and the atmosphere including atmospheric chemistry in both gas and particle phases. In this thesis we studied the in-canopy sources and sinks of BVOCs, the roles of BVOCs in gas and particle phases, as well as the impact of aerosol dynamics on the vertical aerosol fluxes in the planetary boundary layer. Several findings in this thesis are shown below: (1) By using a newly implemented gas dry deposition model in a one-dimensional chemical transport model SOSAA (model to Simulate the concentrations of Organic vapours, Sulphuric Acid and Aerosols) we simulated the in-canopy source and sink terms of 12 featured BVOCs. According to the strength of individual terms, BVOCs were classified into five categories: Cemis in which most of the emitted gases are transported out of the canopy, Cemis-chem in which most of the emitted gases are quickly oxidized inside the canopy, Cemis-depo in which emissions are comparable to deposition, Cdepo in which the dominant deposition sink leads to downward fluxes and Cchem-depo in which the chemical production compensates a part of deposition. (2) High upward fluxes of formic acid over a boreal forest were observed. The required unknown precursors and emission sources were quantified to explain the missing sources inside the canopy. (3) The simulated O3 concentration change due to chemical reactions related to BVOCs was in average less than 10% of the deposition sink. (4) The highly oxidized multifunctional organic molecules (HOMs) play a dominant role in the growth of new particles over the sub-Arctic forest region at the Pallas Atmosphere-Ecosystem Supersite and account for ∼ 75% of total SOA mass during new particle formation events. (5) The modelled vertical aerosol fluxes above the canopy caused by aerosol dynamics were comparable or sometimes exceeded that caused by particle dry deposition. This introduced large biases between measured flux and the particle dry deposition flux. The findings (1), (2), (3), (5) were obtained over the boreal forest at SMEAR (Station for Measuring ecosystem-Atmosphere Relations) II. This thesis provides a new numerical tool to analyse detailed sources and sinks of BVOCs, which can be applied in other ecosystems and further implemented in large-scale models. fi
dc.format.mimetype application/pdf fi
dc.language.iso en fi
dc.publisher Helsingin yliopisto fi
dc.publisher Helsingfors universitet sv
dc.publisher University of Helsinki en
dc.relation.isformatof URN:ISBN:978-952-7276-01-3 fi
dc.relation.isformatof Helsinki: Unigrafia Oy, 2018, 0784-3496 fi
dc.rights Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty. fi
dc.rights This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited. en
dc.rights Publikationen är skyddad av upphovsrätten. Den får läsas och skrivas ut för personligt bruk. Användning i kommersiellt syfte är förbjuden. sv
dc.subject fi
dc.title Sources, sinks and transformation of BVOCs and aerosols in boreal forest boundary layer en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en
dc.type.ontasot Doktorsavhandling (sammanläggning) sv
dc.ths Boy, Michael fi
dc.ths Rannik, Üllar fi
dc.opn Stohl, Andreas fi
dc.type.dcmitype Text fi

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