| 1. |
- Keskinen, H., et al.
(författare)
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Evolution of Nanoparticle Composition in CLOUD in Presence of Sulphuric Acid, Ammonia and Organics
- 2013
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Ingår i: NUCLEATION AND ATMOSPHERIC AEROSOLS. - : American Institute of Physics (AIP). - 9780735411524 ; , s. 291-294
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Konferensbidrag (refereegranskat)abstract
- In this study, we investigate the composition of nucleated nanoparticles formed from sulphuric acid, ammonia, amines, and oxidised organics in the CLOUD chamber experiments at CERN. The investigation is carried out via analysis of the particle hygroscopicity (size range of 15-63 nm), ethanol affinity (15-50nm), oxidation state (<50 nm), and ion composition (few nanometers). The organic volume fraction of particles increased with an increase in particle diameter in presence of the sulphuric acid, ammonia and organics. Vice versa, the sulphuric acid volume fraction decreased when the particle diameter increased. The results provide information on the size-dependent composition of nucleated aerosol particles.
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| 2. |
- Hakkinen, S. A. K., et al.
(författare)
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Semi-empirical parameterization of size-dependent atmospheric nanoparticle growth in continental environments
- 2013
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 13:15, s. 7665-7682
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Tidskriftsartikel (refereegranskat)abstract
- The capability to accurately yet efficiently represent atmospheric nanoparticle growth by biogenic and anthropogenic secondary organics is a challenge for current atmospheric large-scale models. It is, however, crucial to predict nanoparticle growth accurately in order to reliably estimate the atmospheric cloud condensation nuclei (CCN) concentrations. In this work we introduce a simple semi-empirical parameterization for sub-20 nm particle growth that distributes secondary organics to the nanoparticles according to their size and is therefore able to reproduce particle growth observed in the atmosphere. The parameterization includes particle growth by sulfuric acid, secondary organics from monoterpene oxidation (SORG(MT)) and an additional condensable vapor of non-monoterpene organics (background). The performance of the proposed parameterization was investigated using ambient data on particle growth rates in three diameter ranges (1.5-3 nm, 3-7 nm and 7-20 nm). The growth rate data were acquired from particle / air ion number size distribution measurements at six continental sites over Europe. The longest time series of 7 yr (2003-2009) was obtained from a boreal forest site in Hyytiala, Finland, while about one year of data (2008-2009) was used for the other stations. The extensive ambient measurements made it possible to test how well the parameterization captures the seasonal cycle observed in sub-20 nm particle growth and to determine the weighing factors for distributing the SORG(MT) for different sized particles as well as the background mass flux (concentration). Besides the monoterpene oxidation products, background organics with a concentration comparable to SORGMT, around 6x10(7) cm(-3) (consistent with an additional global SOA yield of 100 Tg yr(-1)) was needed to reproduce the observed nanoparticle growth. Simulations with global models suggest that the background could be linked to secondary biogenic organics that are formed in the presence of anthropogenic pollution.
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| 3. |
- Nordin, E. Z., et al.
(författare)
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Secondary organic aerosol formation from idling gasoline passenger vehicle emissions investigated in a smog chamber
- 2013
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 13:12, s. 6101-6116
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Tidskriftsartikel (refereegranskat)abstract
- Gasoline vehicles have recently been pointed out as potentially the main source of anthropogenic secondary organic aerosol (SOA) in megacities. However, there is a lack of laboratory studies to systematically investigate SOA formation in real-world exhaust. In this study, SOA formation from pure aromatic precursors, idling and cold start gasoline exhaust from three passenger vehicles (EURO2-EURO4) were investigated with photo-oxidation experiments in a 6 m(3) smog chamber. The experiments were carried out down to atmospherically relevant organic aerosol mass concentrations. The characterization instruments included a high-resolution aerosol mass spectrometer and a proton transfer mass spectrometer. It was found that gasoline exhaust readily forms SOA with a signature aerosol mass spectrum similar to the oxidized organic aerosol that commonly dominates the organic aerosol mass spectra downwind of urban areas. After a cumulative OH exposure of similar to 5 x 10(6) cm(-3) h, the formed SOA was 1-2 orders of magnitude higher than the primary OA emissions. The SOA mass spectrum from a relevant mixture of traditional light aromatic precursors gave f(43) (mass fraction at m/z = 43), approximately two times higher than to the gasoline SOA. However O:C and H:C ratios were similar for the two cases. Classical C-6-C-9 light aromatic precursors were responsible for up to 60% of the formed SOA, which is significantly higher than for diesel exhaust. Important candidates for additional precursors are higher-order aromatic compounds such as C-10 and C-11 light aromatics, naphthalene and methyl-naphthalenes. We conclude that approaches using only light aromatic precursors give an incomplete picture of the magnitude of SOA formation and the SOA composition from gasoline exhaust.
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| 4. |
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| 5. |
- Nordin, E. Z., et al.
(författare)
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Secondary organic aerosol formation from gasoline passenger vehicle emissions investigated in a smog chamber
- 2012
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Ingår i: Atmospheric Chemistry and Physics Discussions. - : Copernicus Publications. - 1680-7367 .- 1680-7375. ; 12:12, s. 31725-31765
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Tidskriftsartikel (refereegranskat)abstract
- Gasoline vehicles have elevated emissions of volatile organic compounds during cold starts and idling and have recently been pointed out as potentially the main source of anthropogenic secondary organic aerosol (SOA) in megacities. However, there is a lack of laboratory studies to systematically investigate SOA formation in real-world exhaust. In this study, SOA formation from pure aromatic precursors, idling and cold start gasoline exhaust from one Euro II, one Euro III and one Euro IV passenger vehicles were investigated using photo-oxidation experiments in a 6 m3 smog chamber. The experiments were carried out at atmospherically relevant organic aerosol mass concentrations. The characterization methods included a high resolution aerosol mass spectrometer and a proton transfer mass spectrometer. It was found that gasoline exhaust readily forms SOA with a signature aerosol mass spectrum similar to the oxidized organic aerosol that commonly dominates the organic aerosol mass spectra downwind urban areas. After 4 h aging the formed SOA was 1–2 orders of magnitude higher than the Primary OA emissions. The SOA mass spectrum from a relevant mixture of traditional light aromatic precursors gave f43 (mass fraction at m/z = 4 3) approximately two times higher than to the gasoline SOA. However O : C and H : C ratios were similar for the two cases. Classical C6–C9 light aromatic precursors were responsible for up to 60% of the formed SOA, which is significantly higher than for diesel exhaust. Important candidates for additional precursors are higher order aromatic compounds such as C10, C11 light aromatics, naphthalene and methyl-naphthalenes.
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| 6. |
- Almeida, Joao, et al.
(författare)
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Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere
- 2013
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 502:7471, s. 359-
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Tidskriftsartikel (refereegranskat)abstract
- Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei(1). Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes(2). Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases(2). However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere(3). It is thought that amines may enhance nucleation(4-16), but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.
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| 7. |
- Kajos, M. K., et al.
(författare)
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Terpenoid emissions from fully grown east Siberian Larix cajanderi trees
- 2013
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 10:7, s. 4705-4719
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Tidskriftsartikel (refereegranskat)abstract
- While emissions of many biogenic volatile organic compounds (BVOCs), such as terpenoids, have been studied quite intensively in North American and Scandinavian boreal forests, the vast Siberian boreal forests have remained largely unexplored by experimental emission studies. In this study the shoot-scale terpenoid emission rates from two mature Larix cajanderi trees growing in their natural habitat in eastern Siberia were measured at the Spasskaya Pad flux measurement site (62 degrees 15'18.4 '' N, 129 degrees 37'07.9 '' E) located on the western bank of the Lena river. The measurements were conducted during three campaigns: 3-24 June, 8-26 July, and 14-30 August, in the summer of 2009. A dynamic flow-through enclosure technique was applied for adsorbent sampling, and the samples were analysed offline with a gas chromatograph. Between 29 and 45 samples were taken from each shoot during all three campaigns. Seven different monoterpenes, six different sesquiterpenes, linalool isoprene, and 2-methyl-3-buten-2-ol (MBO) were identified. The monthly median value of the total terpenoid emissions varied between 0.006 and 10.6 mu g g(dw)(-1)h(-1). The emissions were dominated by monoterpenes, which constituted between 61 and 92% of the total emissions. About half of the monoterpene emissions were comprised of Delta(3)-carene; alpha- and beta-pinene had significant emissions as well. Linalool emissions were also substantial, comprising 3-37% of the total emissions, especially in June. Sesquiterpenes accounted for less than 3% and isoprene less than 1% of the total emissions. Based on the measured emission rates, the relative atmospheric concentration of each compound was estimated. Monoterpenes were the species with the highest relative concentration, while linalool and sesquiterpenes had a notably smaller contribution to the estimated atmospheric concentration than to the emission rates. A temperature-dependent pool algorithm with a constant beta (0.09 degrees C-1 for monoterpenes and 0.143 degrees C-1 for sesquiterpenes) was used to normalize the measured emission data. For monoterpenes the emission potential varied between 0.5 and 18.5 mu g g(dw)(-1)h(-1) and for sesquiterpenes between 0.02 and 0.4 mu g g(dw)(-1)h(-1).
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