| 1. |
- 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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| 2. |
- Höpner, Friederike, 1986-
(författare)
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Multiple perspectives on absorbing aerosols over the northern Indian Ocean and Asia
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aerosol particles in the atmosphere scatter and absorb solar radiation, and thereby affect the Earth's energy budget, but the magnitude of the overall radiative effect due to aerosol-radiation interactions is uncertain. In particular, the impact of absorbing aerosol particles, mainly black carbon (BC), organic carbon and dust, is not completely understood. A large variety of absorbing aerosols can be found in Asia and over adjacent oceans due to huge urban, biomass burning and desert areas. This thesis focuses on the investigation of atmospheric aerosols over the northern Indian Ocean and Asia from multiple perspectives. This includes surface and vertical observations of physical and chemical particle properties by in-situ and remote sensing instruments as well as an investigation of the representation of absorbing aerosols in general circulation models. One main focus is on the identification of BC-containing particles at the marine remote Maldives Climate Observatory in Hanimaadhoo (MCOH) which is frequently influenced by continental air masses containing anthropogenic aerosols. During an intensive field campaign, vertical measurements of aerosol particles were performed with a Lidar and unmanned aerial vehicles. Elevated layers of absorbing aerosol above the marine boundary layer were found frequently when air masses had their source over the northern Indian Peninsula. However, determining a complete profile of particle absorption only from Lidar measurements is linked to high uncertainties. Long-term surface measurements of particle absorption and scattering together with observations of aerosol chemical composition at MCOH are used to evaluate purely optical methods for aerosol characterization. These optical methods are found to give reasonable estimates of particle types but they can not replace detailed chemical measurements. An additional comparison study of various instruments for determination of BC mass give potentially very diverse results, highlighting the complexity of the quantification of BC-containing particles. The investigation of the representation of absorbing aerosols over Asia in general circulation models reveals firstly that the particle absorption is generally underestimated in global climate models, and secondly that the range in aerosol absorption determined from major changes of emissions, meteorology and particle optical properties can not reach the large inter-model diversity.
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| 3. |
- Rahlff, Janina, et al.
(författare)
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Heads in the clouds : marine viruses disperse bidirectionally along the natural water cycle
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Marine viruses have thoroughly been studied in seawater, yet their dispersal from neuston ecosystems at the air-sea interface towards the atmosphere remains a knowledge gap. Here, we show that 6.2 % of the studied virus population were shared between air-sea interface ecosystems and rainwater. Virus enrichment in the 1-mm thin surface microlayer and sea foams happened selectively, and variant analysis proved virus transfer to aerosols and rain. Viruses detected in rain and aerosols showed a significantly higher percent G/C base content compared to marine viruses, and a genetically distinct rain virome supports that those viruses could inhabit higher air masses. CRISPR spacer matches of marine prokaryotes to foreign viruses from rainwater prove regular virus-host encounters at the air-sea interface. Our findings on aerosolization and long-range atmospheric dispersal implicate virus-mediated carbon turnover in remote areas, viral dispersal mechanisms relevant to human health, and involvement of viruses in atmospheric processes like ice-nucleation.
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| 4. |
- Rahlff, Janina, et al.
(författare)
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Marine viruses disperse bidirectionally along the natural water cycle
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Marine viruses in seawater have frequently been studied, yet their dispersal from neuston ecosystems at the air-sea interface towards the atmosphere remains a knowledge gap. Here, we show that 6.2% of the studied virus population were shared between air-sea interface ecosystems and rainwater. Virus enrichment in the 1-mm thin surface microlayer and sea foams happened selectively, and variant analysis proved virus transfer to aerosols collected at ~2 m height above sea level and rain. Viruses detected in rain and these aerosols showed a significantly higher percent G/C base content compared to marine viruses. CRISPR spacer matches of marine prokaryotes to foreign viruses from rainwater prove regular virus-host encounters at the air-sea interface. Our findings on aerosolization, adaptations, and dispersal support transmission of viruses along the natural water cycle.
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