| 1. |
- Yan, C., et al.
(författare)
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Size-dependent influence of NOx on the growth rates of organic aerosol particles
- 2020
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 6:22
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric new-particle formation (NPF) affects climate by contributing to a large fraction of the cloud condensation nuclei (CCN). Highly oxygenated organic molecules (HOMs) drive the early particle growth and therefore substantially influence the survival of newly formed particles to CCN. Nitrogen oxide (NOx) is known to suppress the NPF driven by HOMs, but the underlying mechanism remains largely unclear. Here, we examine the response of particle growth to the changes of HOM formation caused by NOx. We show that NOx suppresses particle growth in general, but the suppression is rather nonuniform and size dependent, which can be quantitatively explained by the shifted HOM volatility after adding NOx. By illustrating how NOx affects the early growth of new particles, a critical step of CCN formation, our results help provide a refined assessment of the potential climatic effects caused by the diverse changes of NOx level in forest regions around the globe.
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| 2. |
- Kim, J., et al.
(författare)
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Hygroscopicity of nanoparticles produced from homogeneous nucleation in the CLOUD experiments
- 2016
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:1, s. 293-304
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Tidskriftsartikel (refereegranskat)abstract
- Sulfuric acid, amines and oxidized organics have been found to be important compounds in the nucleation and initial growth of atmospheric particles. Because of the challenges involved in determining the chemical composition of objects with very small mass, however, the properties of the freshly nucleated particles and the detailed pathways of their formation processes are still not clear. In this study,we focus on a challenging size range, i.e., particles that have grown to diameters of 10 and 15 nm following nucleation, and measure their water uptake. Water uptake is useful information for indirectly obtaining chemical composition of aerosol particles. We use a nanometer-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) at sub-saturated conditions (ca. 90% relative humidity at 293 K) to measure the hygroscopicity of particles during the seventh Cosmics Leaving OUtdoor Droplets (CLOUD7) campaign performed at CERN in 2012. In CLOUD7, the hygroscopicity of nucleated nanoparticles was measured in the presence of sulfuric acid, sulfuric acid-dimethylamine, and sulfuric acid-organics derived from alpha-pinene oxidation. The hygroscopicity parameter kappa decreased with increasing particle size, indicating decreasing acidity of particles. No clear effect of the sulfuric acid concentration on the hygroscopicity of 10 nm particles produced from sulfuric acid and dimethylamine was observed, whereas the hygroscopicity of 15 nm particles sharply decreased with decreasing sulfuric acid concentrations. In particular, when the concentration of sulfuric acid was 5.1 x 10(6) molecules cm(-3) in the gas phase, and the dimethylamine mixing ratio was 11.8 ppt, the measured kappa of 15 nm particles was 0.31 +/- 0.01: close to the value reported for dimethylaminium sulfate (DMAS) (kappa(DMAS) similar to 0.28). Furthermore, the difference in kappa between sulfuric acid and sulfuric acid-dimethylamine experiments increased with increasing particle size. The kappa values of particles in the presence of sulfuric acid and organics were much smaller than those of particles in the presence of sulfuric acid and dimethylamine. This suggests that the organics produced from alpha-pinene ozonolysis play a significant role in particle growth even at 10 nm sizes.
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| 3. |
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| 4. |
- Hakkinen, S. A. K., et al.
(författare)
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Long-term volatility measurements of submicron atmospheric aerosol in Hyytiala, Finland
- 2012
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 12:22, s. 10771-10786
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Tidskriftsartikel (refereegranskat)abstract
- The volatility of submicron atmospheric aerosol particles was investigated at a boreal forest site in Hyytiala, Finland from January 2008 to May 2010. These long-term observations allowed for studying the seasonal behavior of aerosol evaporation with a special focus on compounds that remained in the aerosol phase at 280 degrees C. The temperature-response of evaporation was also studied by heating the aerosol sample step-wise to six temperatures ranging from 80 degrees C to 280 degrees C. The mass fraction remaining after heating (MFR) was determined from the measured particle number size distributions before and after heating assuming a constant particle density (1.6 g cm(-3)). On average 19% of the total aerosol mass remained in the particulate phase at 280 degrees C. The particles evaporated less at low ambient temperatures during winter as compared with the warmer months. Black carbon (BC) fraction of aerosol mass correlated positively with the MFR at 280 degrees C, but could not explain it completely: most of the time a notable fraction of this nonvolatile residual was something other than BC. Using additional information on ambient meteorological conditions and results from an Aerodyne aerosol mass spectrometer (AMS), the chemical composition of MFR at 280 degrees C and its seasonal behavior was further examined. Correlation analysis with ambient temperature and mass fractions of polycyclic aromatic hydrocarbons (PAHs) indicated that MFR at 280 degrees C is probably affected by anthropogenic emissions. On the other hand, results from the AMS analysis suggested that there may be very low-volatile organics, possibly organonitrates, in the non-volatile (at 280 degrees C) fraction of aerosol mass.
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| 5. |
- 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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| 6. |
- Manninen, H. E., et al.
(författare)
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EUCAARI ion spectrometer measurements at 12 European sites - analysis of new particle formation events
- 2010
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 10:16, s. 7907-7927
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Tidskriftsartikel (refereegranskat)abstract
- We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range similar to 1-42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1-30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.
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| 7. |
- Ahlm, Lars, et al.
(författare)
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Modeling the thermodynamics and kinetics of sulfuric acid-dimethylamine-water nanoparticle growth in the CLOUD chamber
- 2016
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Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 50:10, s. 1017-1032
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Tidskriftsartikel (refereegranskat)abstract
- Dimethylamine (DMA) has a stabilizing effect on sulfuric acid (SA) clusters, and the SA and DMA molecules and clusters likely play important roles in both aerosol particle formation and growth in the atmosphere. We use the monodisperse particle growth model for acid-base chemistry in nanoparticle growth (MABNAG) together with direct and indirect observations from the CLOUD4 and CLOUD7 experiments in the cosmics leaving outdoor droplets (CLOUD) chamber at CERN to investigate the size and composition evolution of freshly formed particles consisting of SA, DMA, and water as they grow to 20nm in dry diameter. Hygroscopic growth factors are measured using a nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA), which combined with simulations of particle water uptake using the thermodynamic extended-aerosol inorganics model (E-AIM) constrain the chemical composition. MABNAG predicts a particle-phase ratio between DMA and SA molecules of 1.1-1.3 for a 2nm particle and DMA gas-phase mixing ratios between 3.5 and 80 pptv. These ratios agree well with observations by an atmospheric-pressure interface time-of-flight (APi-TOF) mass spectrometer. Simulations with MABNAG, direct observations of the composition of clusters <2nm, and indirect observations of the particle composition indicate that the acidity of the nucleated particles decreases as they grow from approximate to 1 to 20nm. However, MABNAG predicts less acidic particles than suggested by the indirect estimates at 10nm diameter using the nano-HTDMA measurements, and less acidic particles than observed by a thermal desorption chemical ionization mass spectrometer (TDCIMS) at 10-30nm. Possible explanations for these discrepancies are discussed.
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| 8. |
- 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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| 9. |
- Kirkby, Jasper, et al.
(författare)
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Ion-induced nucleation of pure biogenic particles
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 521-526
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Kulmala, Markku, et al.
(författare)
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CO2-induced terrestrial climate feedback mechanism : From carbon sink to aerosol source and back
- 2014
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Ingår i: Boreal environment research. - 1239-6095 .- 1797-2469. ; 19, s. 122-131
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Tidskriftsartikel (refereegranskat)abstract
- Feedbacks mechanisms are essential components of our climate system, as they either increase or decrease changes in climate-related quantities in the presence of external forcings. In this work, we provide the first quantitative estimate regarding the terrestrial climate feedback loop connecting the increasing atmospheric carbon dioxide concentration, changes in gross primary production (GPP) associated with the carbon uptake, organic aerosol formation in the atmosphere, and transfer of both diffuse and global radiation. Our approach was to combine process-level understanding with comprehensive, long-term field measurement data set collected from a boreal forest site in southern Finland. Our best estimate of the gain in GPP resulting from the feedback is 1.3 (range 1.02-1.5), which is larger than the gains of the few atmospheric chemistry-climate feedbacks estimated using large-scale models. Our analysis demonstrates the power of using comprehensive field measurements in investigating the complicated couplings between the biosphere and atmosphere on one hand, and the need for complementary approaches relying on the combination of field data, satellite observations model simulations on the other hand.
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| 11. |
- Kyro, E. -M, et al.
(författare)
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Trends in new particle formation in eastern Lapland, Finland : effect of decreasing sulfur emissions from Kola Peninsula
- 2014
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:9, s. 4383-4396
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Tidskriftsartikel (refereegranskat)abstract
- The smelter industry in Kola Peninsula is the largest source of anthropogenic SO2 in the Arctic part of Europe and one of the largest within the Arctic domain. Due to socio-economic changes in Russia, the emissions have been decreasing especially since the late 1990s resulting in decreased SO2 concentrations close to Kola in eastern Lapland, Finland. At the same time, the frequency of new particle formation days has been decreasing distinctively at SMEAR I station in eastern Lapland, especially during spring and autumn. We show that sulfur species, namely sulfur dioxide and sulfuric acid, have an important role in both new particle formation and subsequent growth and that the decrease in new particle formation days is a result of the reduction of sulfur emissions originating from Kola Peninsula. In addition to sulfur species, there are many other quantities, such as formation rate of aerosol particles, condensation sink and nucleation mode particle number concentration, which are related to the number of observed new particle formation (NPF) days and need to be addressed when linking sulfur emissions and NPF. We show that while most of these quantities exhibit statistically significant trends, the reduction in Kola sulfur emissions is the most obvious reason for the rapid decline in NPF days. Sulfuric acid explains approximately 20-50% of the aerosol condensational growth observed at SMEAR I, and there is a large seasonal variation with highest values obtained during spring and autumn. We found that (i) particles form earlier after sunrise during late winter and early spring due to high concentrations of SO2 and H2SO4; (ii) several events occurred during the absence of light, and they were connected to higher than average concentrations of SO2; and (iii) high SO2 concentrations could advance the onset of nucleation by several hours. Moreover, air masses coming over Kola Peninsula seemed to favour new particle formation.
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| 12. |
- Lehtipalo, Katrianne, et al.
(författare)
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The effect of acid-base clustering and ions on the growth of atmospheric nano-particles
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)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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| 13. |
- Tröstl, Jasmin, et al.
(författare)
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The role of low-volatility organic compounds in initial particle growth in the atmosphere
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 527-531
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Tidskriftsartikel (refereegranskat)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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| 14. |
- Wang, Mingyi, et al.
(författare)
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Rapid growth of new atmospheric particles by nitric acid and ammonia condensation
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 581:7807, s. 184-
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Tidskriftsartikel (refereegranskat)abstract
- A list of authors and their affiliations appears at the end of the paper New-particle formation is a major contributor to urban smog(1,2), but how it occurs in cities is often puzzling(3). If the growth rates of urban particles are similar to those found in cleaner environments (1-10 nanometres per hour), then existing understanding suggests that new urban particles should be rapidly scavenged by the high concentration of pre-existing particles. Here we show, through experiments performed under atmospheric conditions in the CLOUD chamber at CERN, that below about +5 degrees Celsius, nitric acid and ammonia vapours can condense onto freshly nucleated particles as small as a few nanometres in diameter. Moreover, when it is cold enough (below -15 degrees Celsius), nitric acid and ammonia can nucleate directly through an acid-base stabilization mechanism to form ammonium nitrate particles. Given that these vapours are often one thousand times more abundant than sulfuric acid, the resulting particle growth rates can be extremely high, reaching well above 100 nanometres per hour. However, these high growth rates require the gas-particle ammonium nitrate system to be out of equilibrium in order to sustain gas-phase supersaturations. In view of the strong temperature dependence that we measure for the gas-phase supersaturations, we expect such transient conditions to occur in inhomogeneous urban settings, especially in wintertime, driven by vertical mixing and by strong local sources such as traffic. Even though rapid growth from nitric acid and ammonia condensation may last for only a few minutes, it is nonetheless fast enough to shepherd freshly nucleated particles through the smallest size range where they are most vulnerable to scavenging loss, thus greatly increasing their survival probability. We also expect nitric acid and ammonia nucleation and rapid growth to be important in the relatively clean and cold upper free troposphere, where ammonia can be convected from the continental boundary layer and nitric acid is abundant from electrical storms(4,5).
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| 15. |
- Wang, Mingyi, et al.
(författare)
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Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 605:7910, s. 483-489
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Tidskriftsartikel (refereegranskat)abstract
- New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN). However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region. Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO3–H2SO4–NH3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.
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| 16. |
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