| 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. |
- 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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| 3. |
- Zabori, Julia, et al.
(författare)
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Comparison between summertime and wintertime Arctic Ocean primary marine aerosol properties
- 2013
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 13:9, s. 4783-4799
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Tidskriftsartikel (refereegranskat)abstract
- Primary marine aerosols (PMAs) are an important source of cloud condensation nuclei, and one of the key elements of the remote marine radiative budget. Changes occurring in the rapidly warming Arctic, most importantly the decreasing sea ice extent, will alter PMA production and hence the Arctic climate through a set of feedback processes. In light of this, laboratory experiments with Arctic Ocean water during both Arctic winter and summer were conducted and focused on PMA emissions as a function of season and water properties. Total particle number concentrations and particle number size distributions were used to characterize the PMA population. A comprehensive data set from the Arctic summer and winter showed a decrease in PMA concentrations for the covered water temperature (T-w) range between - 1 degrees C and 15 degrees C. A sharp decrease in PMA emissions for a T-w increase from -1 degrees C to 4 degrees C was followed by a lower rate of change in PMA emissions for T-w up to about 6 degrees C. Near constant number concentrations for water temperatures between 6 degrees C to 10 degrees C and higher were recorded. Even though the total particle number concentration changes for overlapping T-w ranges were consistent between the summer and winter measurements, the distribution of particle number concentrations among the different sizes varied between the seasons. Median particle number concentrations for a dry diameter (D-p) < 0.125 mu m measured during winter conditions were similar (deviation of up to 3 %), or lower (up to 70 %) than the ones measured during summer conditions (for the same water temperature range). For D-p > 0.125 mu m, the particle number concentrations during winter were mostly higher than in summer (up to 50 %). The normalized particle number size distribution as a function of water temperature was examined for both winter and summer measurements. An increase in T-w from -1 degrees C to 10 degrees C during winter measurements showed a decrease in the peak of relative particle number concentration at about a D-p of 0.180 mu m, while an increase was observed for particles with D-p > 1 mu m. Summer measurements exhibited a relative shift to smaller particle sizes for an increase of T-w in the range 7-11 degrees C. The differences in the shape of the number size distributions between winter and summer may be caused by different production of organic material in water, different local processes modifying the water masses within the fjord (for example sea ice production in winter and increased glacial meltwater inflow during summer) and different origin of the dominant sea water mass. Further research is needed regarding the contribution of these factors to the PMA production.
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