| 1. |
- Almeida, Joao, et al.
(author)
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Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere
- 2013
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 502:7471, s. 359-
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Journal article (peer-reviewed)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. |
- Hrdina, Amy, et al.
(author)
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The role of coarse aerosol particles as a sink of HNO3 in wintertime pollution events in the Salt Lake Valley
- 2021
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:10, s. 8111-8126
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Journal article (peer-reviewed)abstract
- Wintertime ammonium nitrate (NH4NO3) pollution events burden urban mountain basins around the globe. In the Salt Lake Valley of Utah in the United States, such pollution events are often driven by the formation of persistent cold-air pools (PCAPs) that trap emissions near the surface for several consecutive days. As a result, secondary pollutants including fine particulate matter less than 2.5 um in diameter (PM2:5), largely in the form of NH4NO3, build up during these events and lead to severe haze. As part of an extensive measurement campaign to understand the chemical processes underlying PM2:5 formation, the 2017 Utah Winter Fine Particulate Study, water-soluble trace gases and PM2:5 constituents were continuously monitored using the ambient ion monitoring ion chromatograph (AIM-IC) system at the University of Utah campus. Gas-phase NH3, HNO3, HCl, and SO2 along with particulate NHC 4 , NaC, KC, Mg2C, Ca2C, NO3 , Cl, and SO2 4 were measured from 21 January to 21 February 2017. During the two PCAP events captured, the fine particulate matter was dominated by secondary NH4NO3. The comparison of total nitrate (HNO3 CPM2:5 NO3 ) and total NHx (NH3 CPM2:5 NHC 4 ) showed NHx was in excess during both pollution events. However, chemical composition analysis of the snowpack during the first PCAP event revealed that the total concentration of deposited NO3 was nearly 3 times greater than that of deposited NHC 4 . Daily snow composition measurements showed a strong correlation between NO3 and Ca2C in the snowpack. The presence of non-volatile salts (NaC, Ca2C, and Mg2C), which are frequently associated with coarse-mode dust, was also detected in PM2:5 by the AIM-IC during the two PCAP events, accounting for roughly 5% of total mass loading. The presence of a significant particle mass and surface area in the coarse mode during the first PCAP event was indicated by size-resolved particle measurements from an aerodynamic particle sizer. Taken together, these observations imply that atmospheric measurements of the gas-phase and fine-mode particle nitrate may not represent the total burden of nitrate in the atmosphere, implying a potentially significant role for uptake by coarse-mode dust. Using the NO3 :NHC 4 ratio observed in the snowpack to estimate the proportion of atmospheric nitrate present in the coarse mode, we estimate that the amount of secondary NH4NO3 could double in the absence of the coarse-mode sink. The underestimation of total nitrate indicates an incomplete account of the total oxidant production during PCAP events. The ability of coarse particles to permanently remove HNO3 and influence PM2:5 formation is discussed using information about particle composition and size distribution.
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| 3. |
- Kirkby, Jasper, et al.
(author)
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Ion-induced nucleation of pure biogenic particles
- 2016
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 521-526
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Journal article (peer-reviewed)abstract
- Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood(1). Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours(2). It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere(3,4), and that ions have a relatively minor role(5). Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded(6,7). Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of a-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.
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| 4. |
- Kulmala, Markku, et al.
(author)
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Direct Observations of Atmospheric Aerosol Nucleation
- 2013
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 339:6122, s. 943-946
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Journal article (peer-reviewed)abstract
- Atmospheric nucleation is the dominant source of aerosol particles in the global atmosphere and an important player in aerosol climatic effects. The key steps of this process occur in the sub-2-nanometer (nm) size range, in which direct size-segregated observations have not been possible until very recently. Here, we present detailed observations of atmospheric nanoparticles and clusters down to 1-nm mobility diameter. We identified three separate size regimes below 2-nm diameter that build up a physically, chemically, and dynamically consistent framework on atmospheric nucleation-more specifically, aerosol formation via neutral pathways. Our findings emphasize the important role of organic compounds in atmospheric aerosol formation, subsequent aerosol growth, radiative forcing and associated feedbacks between biogenic emissions, clouds, and climate.
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| 5. |
- Lehtipalo, Katrianne, et al.
(author)
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How Do Amines Affect the Growth of Recently Formed Aerosol Particles
- 2013
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In: NUCLEATION AND ATMOSPHERIC AEROSOLS. - : American Institute of Physics (AIP). - 9780735411524 ; , s. 295-297
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Conference paper (peer-reviewed)abstract
- Growth rates of recently born nanometer-scale particles were measured during the CLOUD experiments at CERN. Combining the data from several recently developed measurement techniques allowed us to follow the growth of the particles starting from molecules to molecular clusters and finally to climatically relevant particles. We studied the binary system with sulphuric acid and water, and the ternary systems with ammonia or dimethylamine added to the chamber, both in purely neutral situation, and with ionization from cosmic rays or the CERN particle beam.
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| 6. |
- Lehtipalo, Katrianne, et al.
(author)
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The effect of acid-base clustering and ions on the growth of atmospheric nano-particles
- 2016
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Journal article (peer-reviewed)abstract
- The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.
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| 7. |
- Schobesberger, Siegfried, et al.
(author)
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Airborne measurements over the boreal forest of southern Finland during new particle formation events in 2009 and 2010
- 2013
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In: Boreal environment research. - 1239-6095 .- 1797-2469. ; 18:2, s. 145-163
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Journal article (peer-reviewed)abstract
- Schobesberger, S., Vaananen, R., Leino, K., Virkkula, A., Backman, J., Pohja, T., Siivola, E., Franchin, A., Mikkila, J., Paramonov, M., Aalto, P.P., Krejci, R., Petaja, T. & Kulmala, M. 2013: Airborne measurements over the boreal forest of southern Finland during new particle formation events in 2009 and 2010. Boreal Env. Res. 18: 145-163. We conducted airborne observations of aerosol physical properties over the southern Finland boreal forest environment. The aim was to investigate the lower tropospheric aerosol (up to 4-km altitude) over an area of 250 by 200 km, in particular during new particle formation (NPF) events, and to address the spatial variability of aerosol number concentration and number size distribution. The regional NPF events, detected both airborne and at the ground, with air masses originating from the Arctic or northern Atlantic Ocean were studied throughout the boundary layer and throughout the area covered. Three suitable case studies are presented in more detail. In two of these studies, the concentrations of nucleation mode particles (3-10 nm in diameter) were found considerably higher (up to a factor of 30) in the upper parts of the planetary boundary layer compared to ground-based measurements during the nucleation events. The observed vertical variation can be connected to boundary layer dynamics and interactions between the boundary layer and the lower free troposphere, likely yielding high concentrations of newly formed aerosol particles. Our results suggest that nucleation does not necessarily occur close to the surface. In one presented case we found evidence of NPF occurring in a limited area above cloud, in the complete absence of a regional NPF event.
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| 8. |
- Tröstl, Jasmin, et al.
(author)
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The role of low-volatility organic compounds in initial particle growth in the atmosphere
- 2016
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 527-531
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Journal article (peer-reviewed)abstract
- About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday(1). Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres(2,3). In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles(4), thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth(5,6), leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer(7-10). Although recent studies(11-13) predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon(2), and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Kohler theory)(2,14), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown(15) that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10(-0.5) micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.
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| 9. |
- Tsagkogeorgas, Georgios, et al.
(author)
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Evaporation of sulfate aerosols at low relative humidity
- 2017
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:14, s. 8923-8938
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Journal article (peer-reviewed)abstract
- Evaporation of sulfuric acid from particles can be important in the atmospheres of Earth and Venus. However, the equilibrium constant for the dissociation of H2SO4 to bisulfate ions, which is the one of the fundamental parameters controlling the evaporation of sulfur particles, is not well constrained. In this study we explore the volatility of sulfate particles at very low relative humidity. We measured the evaporation of sulfur particles versus temperature and relative humidity in the CLOUD chamber at CERN. We modelled the observed sulfur particle shrinkage with the ADCHAM model. Based on our model results, we conclude that the sulfur particle shrinkage is mainly governed by H2SO4 and potentially to some extent by SO3 evaporation. We found that the equilibrium constants for the dissociation of H2SO4 to HSO4-(KH2SO4) and the dehydration of H2SO4 to SO3 (KSO3) are KH2SO4 Combining double low line 2-4 × 109 kg-1 and KSO3 ≥ 1.4 × g 1010 at 288.8± 5K.
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| 10. |
- Wimmer, Daniela, et al.
(author)
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Ground-based observation of clusters and nucleation-mode particles in the Amazon
- 2018
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:17, s. 13245-13264
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Journal article (peer-reviewed)abstract
- We investigated atmospheric new particle formation (NPF) in the Amazon rainforest using direct measurement methods. To our knowledge this is the first direct observation of NPF events in the Amazon region. However, previous observations elsewhere in Brazil showed the occurrence of nucleation-mode particles. Our measurements covered two field sites and both the wet and dry season. We measured the variability of air ion concentrations (0.8-12 nm) with an ion spectrometer between September 2011 and January 2014 at a rainforest site (T0t). Between February and October 2014, the same measurements were performed at a grassland pasture site (T3) as part of the GoAmazon 2014/5 experiment, with two intensive operating periods (IOP1 and IOP2 during the wet and the dry season, respectively). The GoAmazon 2014/5 experiment was designed to study the influence of anthropogenic emissions on the changing climate in the Amazon region. The experiment included basic aerosol and trace gas measurements at the ground, remote sensing instrumentation, and two aircraft-based measurements. The results presented in this work are from measurements performed at ground level at both sites. The site inside the rainforest (T0t) is located 60 km NNW of Manaus and influenced by pollution about once per week. The pasture (T3) site is located 70 km downwind from Manaus and influenced by the Manaus pollution plume typically once per day or every second day, especially in the afternoon. No NPF events were observed inside the rainforest (site T0t) at ground level during the measurement period. However, rain-induced ion and particle bursts (hereafter, rain events) occurred frequently (643 of 1031 days) at both sites during the wet and dry season, being most frequent during the wet season. During the rain events, the ion concentrations in three size ranges (0.8-2, 2-4, and 4-12 nm) increased up to about 10(4)-10(5) cm(-3). This effect was most pronounced in the intermediate and large size ranges, for which the background ion concentrations were about 10-15 cm(-3) compared with 700 cm(-3) for the cluster ion background. We observed eight NPF events at the pasture site during the wet season. We calculated the growth rates and formation rates of neutral particles and ions for the size ranges 2-3 and 3-7 nm using the ion spectrometer data. The observed median growth rates were 0.8 and 1.6 nm h(-1) for 2-3 nm sized ions and particles, respectively, with larger growth rates (13.3 and 7.9 nm h(-1)) in the 3-7 nm size range. The measured nucleation rates were of the order of 0.2 cm(-3) s(-1) for particles and 4-9 x 10(-3) cm(-3) s(-1) for ions. There was no clear difference in the sulfuric acid concentrations between the NPF event days and nonevent days (similar to 9 x 10(5) cm(-3)). The two major differences between the NPF days and nonevent days were a factor of 1.8 lower condensation sink on NPF event days (1.8 x 10(-3) s(-1)) compared to nonevents (3.2 x 10(-3) s(-1)) and different air mass origins. To our knowledge, this is the first time that results from ground-based sub-3 nm aerosol particle measurements have been obtained from the Amazon rainforest.
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