Browsing by Subject "NEUTRAL CLUSTER"

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  • Stolzenburg, Dominik; Simon, Mario; Ranjithkumar, Ananth; Kuerten, Andreas; Lehtipalo, Katrianne; Gordon, Hamish; Ehrhart, Sebastian; Finkenzeller, Henning; Pichelstorfer, Lukas; Nieminen, Tuomo; Brilke, Sophia; Xiao, Mao; Amorim, Antonio; Baalbaki, Rima; Baccarini, Andrea; Beck, Lisa; Brakling, Steffen; Murillo, Lucia Caudillo; Chen, Dexian; Chu, Biwu; Dada, Lubna; Dias, Antonio; Dommen, Josef; Duplissy, Jonathan; El Haddad, Imad; Fischer, Lukas; Carracedo, Loic Gonzalez; Heinritzi, Martin; Kim, Changhyuk; Koenig, Theodore K.; Kong, Weimeng; Lamkaddam, Houssni; Lee, Chuan Ping; Leiminger, Markus; Li, Zijun; Makhmutov, Vladimir; Manninen, Hanna E.; Marie, Guillaume; Marten, Ruby; Mueller, Tatjana; Nie, Wei; Partoll, Eva; Petaja, Tuukka; Pfeifer, Joschka; Philippov, Maxim; Rissanen, Matti P.; Rorup, Birte; Schobesberger, Siegfried; Schuchmann, Simone; Shen, Jiali; Sipila, Mikko; Steiner, Gerhard; Stozhkov, Yuri; Tauber, Christian; Tham, Yee Jun; Tome, Antonio; Vazquez-Pufleau, Miguel; Wagner, Andrea C.; Wang, Mingyi; Wang, Yonghong; Weber, Stefan K.; Wimmer, Daniela; Wlasits, Peter J.; Wu, Yusheng; Ye, Qing; Zauner-Wieczorek, Marcel; Baltensperger, Urs; Carslaw, Kenneth S.; Curtius, Joachim; Donahue, Neil M.; Flagan, Richard C.; Hansel, Armin; Kulmala, Markku; Lelieveld, Jos; Volkamer, Rainer; Kirkby, Jasper; Winkler, Paul M.; He, Xucheng (2020)
    In the present-day atmosphere, sulfuric acid is the most important vapour for aerosol particle formation and initial growth. However, the growth rates of nanoparticles (<10 nm) from sulfuric acid remain poorly measured. Therefore, the effect of stabilizing bases, the contribution of ions and the impact of attractive forces on molecular collisions are under debate. Here, we present precise growth rate measurements of uncharged sulfuric acid particles from 1.8 to 10 nm, performed under atmospheric conditions in the CERN (European Organization for Nuclear Research) CLOUD chamber. Our results show that the evaporation of sulfuric acid particles above 2 nm is negligible, and growth proceeds kinetically even at low ammonia concentrations. The experimental growth rates exceed the hard-sphere kinetic limit for the condensation of sulfuric acid. We demonstrate that this results from van derWaals forces between the vapour molecules and particles and disentangle it from charge-dipole interactions. The magnitude of the enhancement depends on the assumed particle hydration and collision kinetics but is increasingly important at smaller sizes, resulting in a steep rise in the observed growth rates with decreasing size. Including the experimental results in a global model, we find that the enhanced growth rate of sulfuric acid particles increases the predicted particle number concentrations in the upper free troposphere by more than 50 %.
  • Franchin, A.; Ehrhart, S.; Leppä, J.; Nieminen, T.; Gagné, S.; Schobesberger, S.; Wimmer, D.; Duplissy, J.; Riccobono, F.; Dunne, E.M.; Rondo, L.; Downard, A.; Bianchi, F.; Kupc, A.; Tsagkogeorgas, G.; Lehtipalo, K.; Manninen, H.E.; Almeida, J.; Amorim, A.; Wagner, P.E.; Hansel, A.; Kirkby, J.; Kürten, A.; Donahue, N.M.; Makhmutov, V.; Mathot, S.; Metzger, A.; Petäjä, T.; Schnitzhofer, R.; Sipilä, M.; Stozhkov, Y.; Tomé, A.; Kerminen, V.-M.; Carslaw, K.; Curtius, J.; Baltensperger, U.; Kulmala, M. (2015)
    We present the results of laboratory measurements of the ion-ion recombination coefficient at different temperatures, relative humidities and concentrations of ozone and sulfur dioxide. The experiments were carried out using the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at CERN, the walls of which are made of conductive material, making it possible to measure small ions. We produced ions in the chamber using a 3.5 GeV c(-1) beam of positively charged pions (pi(+)) generated by the CERN Proton Synchrotron (PS). When the PS was switched off, galactic cosmic rays were the only ionization source in the chamber. The range of the ion production rate varied from 2 to 100 cm(-3) s(-1), covering the typical range of ionization throughout the troposphere. The temperature ranged from -55 to 20 degrees C, the relative humidity (RH) from 0 to 70 %, the SO2 concentration from 0 to 40 ppb, and the ozone concentration from 200 to 700 ppb. The best agreement of the retrieved ion-ion recombination coefficient with the commonly used literature value of 1.6 x 10(-6) cm(3) s(-1) was found at a temperature of 5 degrees C and a RH of 40% (1.5 +/- 0.6) x 10(-6) cm(3) s(-1). At 20 degrees C and 40% RH, the retrieved ion-ion recombination coefficient was instead (2.3 +/- 0.7) x 10(-6) cm(3) s(-1). We observed no dependency of the ion-ion recombination coefficient on ozone concentration and a weak variation with sulfur dioxide concentration. However, we observed a more than fourfold increase in the ion-ion recombination coefficient with decreasing temperature. We compared our results with three different models and found an overall agreement for temperatures above 0 degrees C, but a disagreement at lower temperatures. We observed a strong increase in the recombination coefficient for decreasing relative humidities, which has not been reported previously.
  • Wimmer, Daniela; Mazon, Stephany Buenrostro; Manninen, Hanna Elina; Kangasluoma, Juha; Franchin, Alessandro; Nieminen, Tuomo; Backman, John; Wang, Jian; Kuang, Chongai; Krejci, Radovan; Brito, Joel; Morais, Fernando Goncalves; Martin, Scot Turnbull; Artaxo, Paulo; Kulmala, Markku; Kerminen, Veli-Matti; Petäjä, Tuukka (2018)
    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.
  • Chen, Xuemeng; Kerminen, Veli-Matti; Paatero, Jussi; Paasonen, Pauli; Manninen, Hanna E.; Nieminen, Tuomo; Petäjä, Tuukka; Kulmala, Markku (2016)
    Most of the ion production in the atmosphere is attributed to ionising radiation. In the lower atmosphere, ionising radiation consists mainly of the decay emissions of radon and its progeny, gamma radiation of the terrestrial origin as well as photons and elementary particles of cosmic radiation. These types of radiation produce ion pairs via the ionisation of nitrogen and oxygen as well as trace species in the atmosphere, the rate of which is defined as the ionising capacity. Larger air ions are produced out of the initial charge carriers by processes such as clustering or attachment to preexisting aerosol particles. This study aimed (1) to identify the key factors responsible for the variability in ionising radiation and in the observed air ion concentrations, (2) to reveal the linkage between them and (3) to provide an in-depth analysis into the effects of ionising radiation on air ion formation, based on measurement data collected during 2003-2006 from a boreal forest site in southern Finland. In general, gamma radiation dominated the ion production in the lower atmosphere. Variations in the ionising capacity came from mixing layer dynamics, soil type and moisture content, meteorological conditions, long-distance transportation, snow cover attenuation and precipitation. Slightly similar diurnal patterns to variations in the ionising capacity were observed in air ion concentrations of the cluster size (0.8-1.7 nm in mobility diameters). However, features observed in the 0.81 nm ion concentration were in good connection to variations of the ionising capacity. Further, by carefully constraining perturbing variables, a strong dependency of the cluster ion concentration on the ionising capacity was identified, proving the functionality of ionising radiation in air ion production in the lower atmosphere. This relationship, however, was only clearly observed on new particle formation (NPF) days, possibly indicating that charges after being born underwent different processes on NPF days and non-event days and also that the transformation of newly formed charges to cluster ions occurred in a shorter timescale on NPF days than on non-event days.
  • Kontkanen, Jenni; Lehtipalo, Katrianne; Ahonen, Lauri; Kangasluoma, Juha; Manninen, Hanna E.; Hakala, Jani; Rose, Clemence; Sellegri, Karine; Xiao, Shan; Wang, Lin; Qi, Ximeng; Nie, Wei; Ding, Aijun; Yu, Huan; Lee, Shanhu; Kerminen, Veli-Matti; Petäjä, Tuukka; Kulmala, Markku (2017)
    The measurement of sub-3 nm aerosol particles is technically challenging. Therefore, there is a lack of knowledge about the concentrations of atmospheric sub-3 nm particles and their variation in different environments. In this study, the concentrations of similar to 1-3 nm particles measured with a particle size magnifier (PSM) were investigated at nine sites around the world. Sub-3 nm particle concentrations were highest at the sites with strong anthropogenic influence. In boreal forest, measured particle concentrations were clearly higher in summer than in winter, suggesting the importance of biogenic precursor vapors in this environment. At all sites, sub-3 nm particle concentrations had daytime maxima, which are likely linked to the photochemical production of precursor vapors and the emissions of precursor vapors or particles from different sources. When comparing ion concentrations to the total sub-3 nm particle concentrations, electrically neutral particles were observed to dominate in polluted environments and in boreal forest during spring and summer. Generally, the concentrations of sub-3 nm particles seem to be determined by the availability of precursor vapors rather than the level of the sink caused by preexisting aerosol particles. The results also indicate that the formation of the smallest particles and their subsequent growth to larger sizes are two separate processes, and therefore studying the concentration of sub-3 nm particles separately in different size ranges is essential.
  • Junninen, Heikki; Duplissy, Jonathan; Ehn, Mikael; Sipilä, Mikko; Kangasluoma, Juha; Franchin, Alessandro; Petäjä, Tuukka; Manninen, Hanna E.; Kerminen, Veli-Matti; Worsnop, Douglas; Kulmala, Markku (2016)
    Atmospheric ions are produced after a cascade of reactions starting from initial ionization by high energetic radiation. Such ionization bursts generate ions that rapidly react and generate a suite of ion products. Primary ions are in the atmosphere originate from radioactive decay, gamma radiation from the soil or cosmic ray events. In this work, we modified an existing instrumentation and developed a novel setup for detecting ion bursts. The setup consists of a continuous flow ionization chamber coupled to Atmospheric Pressure interface Time-Of-Flight (APi-TOF) mass spectrometer. The APi-TOF sampling rate was set to 100 Hz in order to detect individual ion bursts from ionization events. Besides counting the individual ionization events, the developed setup is able to follow the rapidly changing chemical composition of ions during ion burst cascade. The setup can give us insights into the primary ionization mechanisms and their importance in atmospheric ion and aerosol dynamics.
  • Lehtipalo, Katrianne; Yan, Chao; Dada, Lubna; Bianchi, Federico; Xiao, Mao; Wagner, Robert; Stolzenburg, Dominik; Ahonen, Lauri R.; Amorim, Antonio; Baccarini, Andrea; Bauer, Paulus S.; Baumgartner, Bernhard; Bergen, Anton; Bernhammer, Anne-Kathrin; Breitenlechner, Martin; Brilke, Sophia; Buchholz, Angela; Mazon, Stephany Buenrostro; Chen, Dexian; Chen, Xuemeng; Dias, Antonio; Dommen, Josef; Draper, Danielle C.; Duplissy, Jonathan; Ehn, Mikael; Finkenzeller, Henning; Fischer, Lukas; Frege, Carla; Fuchs, Claudia; Garmash, Olga; Gordon, Hamish; Hakala, Jani; He, Xucheng; Heikkinen, Liine; Heinritzi, Martin; Helm, Johanna C.; Hofbauer, Victoria; Hoyle, Christopher R.; Jokinen, Tuija; Kangasluoma, Juha; Kerminen, Veli-Matti; Kim, Changhyuk; Kirkby, Jasper; Kontkanen, Jenni; Kuerten, Andreas; Lawler, Michael J.; Mai, Huajun; Mathot, Serge; Mauldin, Roy L.; Molteni, Ugo; Nichman, Leonid; Nie, Wei; Nieminen, Tuomo; Ojdanic, Andrea; Onnela, Antti; Passananti, Monica; Petäjä, Tuukka; Piel, Felix; Pospisilova, Veronika; Quelever, Lauriane L. J.; Rissanen, Matti P.; Rose, Clémence; Sarnela, Nina; Schallhart, Simon; Schuchmann, Simone; Sengupta, Kamalika; Simon, Mario; Sipilä, Mikko; Tauber, Christian; Tome, Antonio; Trostl, Jasmin; Väisänen, Olli; Vogel, Alexander L.; Volkamer, Rainer; Wagner, Andrea C.; Wang, Mingyi; Weitz, Lena; Wimmer, Daniela; Ye, Penglin; Ylisirniö, Arttu; Zha, Qiaozhi; Carslaw, Kenneth S.; Curtius, Joachim; Donahue, Neil M.; Flagan, Richard C.; Hansel, Armin; Riipinen, Ilona; Virtanen, Annele; Winkler, Paul M.; Baltensperger, Urs; Kulmala, Markku; Worsnop, Douglas R. (2018)
    A major fraction of atmospheric aerosol particles, which affect both air quality and climate, form from gaseous precursors in the atmosphere. Highly oxygenated organic molecules (HOMs), formed by oxidation of biogenic volatile organic compounds, are known to participate in particle formation and growth. However, it is not well understood how they interact with atmospheric pollutants, such as nitrogen oxides (NOx) and sulfur oxides (SOx) from fossil fuel combustion, as well as ammonia (NH3) from livestock and fertilizers. Here, we show how NOx suppresses particle formation, while HOMs, sulfuric acid, and NH3 have a synergistic enhancing effect on particle formation. We postulate a novel mechanism, involving HOMs, sulfuric acid, and ammonia, which is able to closely reproduce observations of particle formation and growth in daytime boreal forest and similar environments. The findings elucidate the complex interactions between biogenic and anthropogenic vapors in the atmospheric aerosol system.
  • Kecorius, Simonas; Vogl, Teresa; Paasonen, Pauli; Lampilahti, Janne; Rothenberg, Daniel; Wex, Heike; Zeppenfeld, Sebastian; van Pinxteren, Manuela; Hartmann, Markus; Henning, Silvia; Gong, Xianda; Welti, Andre; Kulmala, Markku; Stratmann, Frank; Herrmann, Hartmut; Wiedensohler, Alfred (2019)
    In a warming Arctic the increased occurrence of new particle formation (NPF) is believed to originate from the declining ice coverage during summertime. Understanding the physico-chemical properties of newly formed particles, as well as mechanisms that control both particle formation and growth in this pristine environment, is important for interpreting aerosol-cloud interactions, to which the Arctic climate can be highly sensitive. In this investigation, we present the analysis of NPF and growth in the high summer Arctic. The measurements were made on-board research vessel Polarstern during the PS106 Arctic expedition. Four distinctive NPF and subsequent particle growth events were observed, during which particle (diameter in a range 10-50 nm) number concentrations increased from background values of approx. 40 up to 4000 cm(-3). Based on particle formation and growth rates, as well as hygroscopicity of nucleation and the Aitken mode particles, we distinguished two different types of NPF events. First, some NPF events were favored by negative ions, resulting in more-hygroscopic nucleation mode particles and suggesting sulfuric acid as a precursor gas. Second, other NPF events resulted in less-hygroscopic particles, indicating the influence of organic vapors on particle formation and growth. To test the climatic relevance of NPF and its influence on the cloud condensation nuclei (CCN) budget in the Arctic, we applied a zero-dimensional, adiabatic cloud parcel model. At an updraft velocity of 0.1 m s(-1), the particle number size distribution (PNSD) generated during nucleation processes resulted in an increase in the CCN number concentration by a factor of 2 to 5 compared to the background CCN concentrations. This result was confirmed by the directly measured CCN number concentrations. Although particles did not grow beyond 50 nm in diameter and the activated fraction of 15-50 nm particles was on average below 10 %, it could be shown that the sheer number of particles produced by the nucleation process is enough to significantly influence the background CCN number concentration. This implies that NPF can be an important source of CCN in the Arctic. However, more studies should be conducted in the future to understand mechanisms of NPF, sources of precursor gases and condensable vapors, as well as the role of the aged nucleation mode particles in Arctic cloud formation.
  • Kangasluoma, Juha; Cai, Runlong; Jiang, Jingkun; Deng, Chenjuan; Stolzenburg, Dominik; Ahonen, Lauri R.; Chan, Tommy; Fu, Yueyun; Kim, Changhyuk; Laurila, Tiia M.; Zhou, Ying; Dada, Lubna; Sulo, Juha; Flagan, Richard C.; Kulmala, Markku; Petaja, Tuukka; Lehtipalo, Katrianne (2020)
    Interest in understanding gas-to-particle phase transformation in several disciplines such as at-mospheric sciences, material synthesis, and combustion has led to the development of several distinct instruments that can measure the particle size distributions down to the sizes of large molecules and molecular clusters, at which the initial particle formation and growth takes place. These instruments, which include the condensation particle counter battery, a variety of electrical mobility spectrometers and the particle size magnifier, have been usually characterized in lab-oratory experiments using carefully prepared calibration aerosols. They are then applied, alone or in combination, to study the gas-to-particle transition in experiments that produce particles with a wide range of compositions and other properties. Only a few instrument intercomparisons in either laboratory or field conditions have been reported, raising the question: how accurately can the sub-10 nm particle number size distributions be measured with the currently available instrumentation? Here, we review previous studies in which sub-10 nm particle size distributions have been measured with at least two independent instruments. We present recent data from three sites that deploy the current state-of-the-art instrumentation: Hyytiala, Beijing, and the CLOUD chamber. After discussing the status of the sub-10 nm size distribution measurements, we present a comprehensive uncertainty analysis for these methods that suggests that our present understanding on the sources of uncertainties quite well captures the observed deviations be-tween different instruments in the size distribution measurements. Finally, based on present understanding of the characteristics of a number of systems in which gas-to-particle conversion takes place, and of the instrumental limitations, we suggest guidelines for selecting suitable in-struments for various applications.
  • Dada, Lubna; Chellapermal, Robert; Mazon, Stephany Buenrostro; Paasonen, Pauli; Lampilahti, Janne; Manninen, Hanna E.; Junninen, Heikki; Petäjä, Tuukka; Kerminen, Veli-Matti; Kulmala, Markku (2018)
    Atmospheric new-particle formation (NPF) is a worldwide-observed phenomenon that affects the human health and the global climate. With a growing network of global atmospheric measurement stations, efforts towards investigating NPF have increased. In this study, we present an automated method to classify days into four categories including NPF events, non-events and two classes in between, which then ensures reproducibility and minimizes the hours spent on manual classification. We applied our automated method to 10 years of data collected at the SMEAR II measurement station in Hyytiala, southern Finland using a Neutral cluster and Air Ion Spectrometer (NAIS). In contrast to the traditionally applied classification methods, which categorize days into events and non-events and ambiguous days as undefined days, our method is able to classify the undefined days as it accesses the initial steps of NPF at sub-3 nm sizes. Our results show that, on similar to 24% of the days in Hyytiala, a regional NPF event occurred and was characterized by nice weather and favourable conditions such as a clear sky and low condensation sink. Another class found in Hyytiala is the transported event class, which seems to be NPF carried horizontally or vertically to our measurement location and it occurred on 17% of the total studied days. Additionally, we found that an ion burst, wherein the ions apparently fail to grow to larger sizes, occurred on 18% of the days in Hyytiala. The transported events and ion bursts were characterized by less favourable ambient conditions than regional NPF events and thus experienced interrupted particle formation or growth. Non-events occurred on 41% of the days and were characterized by complete cloud cover and high relative humidity. Moreover, for regional NPF events occurring at the measurement site, the method identifies the start time, peak time and end time, which helps us focus on variables within an exact time window to better understand NPF at a process level. Our automated method can be modified to work in other measurement locations where NPF is observed.
  • Jokinen, Tuija; Kontkanen, Jenni; Lehtipalo, Katrianne; Manninen, Hanna E.; Aalto, Juho; Porcar-Castell, Albert; Garmash, Olga; Nieminen, Tuomo; Ehn, Mikael; Kangasluoma, Juha; Junninen, Heikki; Levula, Janne; Duplissy, Jonathan; Ahonen, Lauri R.; Rantala, Pekka; Heikkinen, Liine; Yan, Chao; Sipila, Mikko; Worsnop, Douglas R.; Back, Jaana; Petäjä, Tuukka; Kerminen, Veli-Matti; Kulmala, Markku (2017)
    Solar eclipses provide unique possibilities to investigate atmospheric processes, such as new particle formation (NPF), important to the global aerosol load and radiative balance. The temporary absence of solar radiation gives particular insight into different oxidation and clustering processes leading to NPF. This is crucial because our mechanistic understanding on how NPF is related to photochemistry is still rather limited. During a partial solar eclipse over Finland in 2015, we found that this phenomenon had prominent effects on atmospheric on-going NPF. During the eclipse, the sources of aerosol precursor gases, such as sulphuric acid and nitrogen-containing highly oxidised organic compounds, decreased considerably, which was followed by a reduced formation of small clusters and nanoparticles and thus termination of NPF. After the eclipse, aerosol precursor molecule concentrations recovered and reinitiated NPF. Our results provide direct evidence on the key role of the photochemical production of sulphuric acid and highly oxidized organic compounds in maintaining atmospheric NPF. Our results also explain the rare occurrence of this phenomenon under dark conditions, as well as its seemingly weak connection with atmospheric ions.
  • Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kuerten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Sipilä, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, Joao; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J.; Dunne, Eimear M.; Flagan, Richard C.; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J.; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K.; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P.; Ruuskanen, Taina; Santos, Filipe D.; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N.; Trostl, Jasmin; Tsagkogeorgas, Georgios; Tome, Antonio; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E.; Wagner, Paul E.; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M.; Virtanen, Annele; Donahue, Neil M.; Carslaw, Kenneth S.; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R.; Kulmala, Markku (2016)
    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.
  • Kulmala, Markku; Horrak, Urmas; Manninen, Hanna E.; Mirme, Sander; Noppel, Madis; Lehtipalo, Katrianne; Junninen, Heikki; Vehkamäki, Hanna; Kerminen, Veli-Matti; Noe, Steffen M.; Tammet, Hannes (2016)
    Atmospheric air ions, clusters and aerosol particles participate in a variety of atmospheric processes and considerably affect e.g. global climate and human health. When measured, air ions as well as atmospheric clusters and particles have been observed to be present practically always and everywhere. In this overview, we present a brief summary of the main achievements and legacy of the series of workshops organized mainly by the University of Helsinki and the University of Tartu. The legacy covers the development and standardization of new instruments, such as ion spectrometers, mass spectrometers and aerosol particle counters, as well as work toward theoretical understanding of new-particle formation and evolution of atmospheric clusters. One important legacy is the establishment of the SMEAR-Estonia station at Jarvselja.
  • Wagner, Robert; Yan, Chao; Lehtipalo, Katrianne; Duplissy, Jonathan; Nieminen, Tuomo; Kangasluoma, Juha; Ahonen, Lauri R.; Dada, Lubna; Kontkanen, Jenni; Manninen, Hanna E.; Dias, Antonio; Amorim, Antonio; Bauer, Paulus S.; Bergen, Anton; Bernhammer, Anne-Kathrin; Bianchi, Federico; Brilke, Sophia; Mazon, Stephany Buenrostro; Chen, Xuemeng; Draper, Danielle C.; Fischer, Lukas; Frege, Carla; Fuchs, Claudia; Garmash, Olga; Gordon, Hamish; Hakala, Jani; Heikkinen, Liine; Heinritzi, Martin; Hofbauer, Victoria; Hoyle, Christopher R.; Kirkby, Jasper; Kurten, Andreas; Kvashnin, Alexander N.; Laurila, Tiia; Lawler, Michael J.; Mai, Huajun; Makhmutov, Vladimir; Mauldin III, Roy L.; Molteni, Ugo; Nichman, Leonid; Nie, Wei; Ojdanic, Andrea; Onnela, Antti; Piel, Felix; Quelever, Lauriane L. J.; Rissanen, Matti P.; Sarnela, Nina; Schallhart, Simon; Sengupta, Kamalika; Simon, Mario; Stolzenburg, Dominik; Stozhkov, Yuri; Trostl, Jasmin; Viisanen, Yrjö; Vogel, Alexander L.; Wagner, Andrea C.; Xiao, Mao; Ye, Penglin; Baltensperger, Urs; Curtius, Joachim; Donahue, Neil M.; Flagan, Richard C.; Gallagher, Martin; Hansel, Armin; Smith, James N.; Tome, Antonio; Winkler, Paul M.; Worsnop, Douglas; Ehn, Mikael; Sipilä, Mikko; Kerminen, Veli-Matti; Petäjä, Tuukka; Kulmala, Markku (2017)
    The formation of secondary particles in the atmosphere accounts for more than half of global cloud condensation nuclei. Experiments at the CERN CLOUD (Cosmics Leaving OUtdoor Droplets) chamber have underlined the importance of ions for new particle formation, but quantifying their effect in the atmosphere remains challenging. By using a novel instrument setup consisting of two nanoparticle counters, one of them equipped with an ion filter, we were able to further investigate the ion-related mechanisms of new particle formation. In autumn 2015, we carried out experiments at CLOUD on four systems of different chemical compositions involving monoterpenes, sulfuric acid, nitrogen oxides, and ammonia. We measured the influence of ions on the nucleation rates under precisely controlled and atmospherically relevant conditions. Our results indicate that ions enhance the nucleation process when the charge is necessary to stabilize newly formed clusters, i.e., in conditions in which neutral clusters are unstable. For charged clusters that were formed by ion-induced nucleation, we were able to measure, for the first time, their progressive neutralization due to recombination with oppositely charged ions. A large fraction of the clusters carried a charge at 1.5 nm diameter. However, depending on particle growth rates and ion concentrations, charged clusters were largely neutralized by ion-ion recombination before they grew to 2.5 nm. At this size, more than 90% of particles were neutral. In other words, particles may originate from ion-induced nucleation, although they are neutral upon detection at diameters larger than 2.5 nm. Observations at Hyytiala, Finland, showed lower ion concentrations and a lower contribution of ion-induced nucleation than measured at CLOUD under similar conditions. Although this can be partly explained by the observation that ion-induced fractions decrease towards lower ion concentrations, further investigations are needed to resolve the origin of the discrepancy.