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  • Xausa, Filippo; Paasonen, Pauli; Makkonen, Risto; Arshinov, Mikhail; Ding, Aijun; Van Der Gon, Hugo Denier; Kerminen, Veli-Matti; Kulmala, Markku (2018)
    Climate models are important tools that are used for generating climate change projections, in which aerosol-climate interactions are one of the main sources of uncertainties. In order to quantify aerosol-radiation and aerosolcloud interactions, detailed input of anthropogenic aerosol number emissions is necessary. However, the anthropogenic aerosol number emissions are usually converted from the corresponding mass emissions in pre-compiled emission inventories through a very simplistic method depending uniquely on chemical composition, particle size and density, which are defined for a few, very wide main source sectors. In this work, the anthropogenic particle number emissions converted from the AeroCom mass in the ECHAM-HAM climate model were replaced with the recently formulated number emissions from the Greenhouse Gas and Air Pollution Interactions and Synergies (GAINS) model. In the GAINS model the emission number size distributions vary, for example, with respect to the fuel and technology. Special attention was paid to accumulation mode particles (particle diameter d(p) > 100 nm) because of (i) their capability of acting as cloud condensation nuclei (CCN), thus forming cloud droplets and affecting Earth's radiation budget, and (ii) their dominant role in forming the coagulation sink and thus limiting the concentration of sub-100 nm particles. In addition, the estimates of anthropogenic CCN formation, and thus the forcing from aerosol-climate interactions, are expected to be affected. Analysis of global particle number concentrations and size distributions reveals that GAINS implementation increases CCN concentration compared with AeroCom, with regional enhancement factors reaching values as high as 10. A comparison between modeled and observed concentrations shows that the increase in number concentration for accumulation mode particles agrees well with measurements, but it leads to a consistent underestimation of both nucleation mode and Aitken mode (d(p) <100 nm) particle number concentrations. This suggests that revisions are needed in the new particle formation and growth schemes currently applied in global modeling frameworks.
  • Qi, X. M.; Ding, A. J.; Nie, W.; Petäjä, T.; Kerminen, V. -M.; Herrmann, E.; Xie, Y. N.; Zheng, L. F.; Manninen, H.; Aalto, P.; Sun, J. N.; Xu, Z. N.; Chi, X. G.; Huang, X.; Boy, M.; Virkkula, A.; Yang, X. -Q.; Fu, C. B.; Kulmala, M. (2015)
    Aerosol particles play important roles in regional air quality and global climate change. In this study, we analyzed 2 years (2011-2013) of measurements of submicron particles (6-800 nm) at a suburban site in the western Yangtze River Delta (YRD) of eastern China. The number concentrations (NCs) of particles in the nucleation, Aitken and accumulation modes were 5300 +/- 5500, 8000 +/- 4400, 5800 +/- 3200 cm(-3), respectively. The NCs of total particles are comparable to those at urban/suburban sites in other Chinese megacities, such as Beijing, but about 10 times higher than in the remote western China. Long-range and regional transport largely influenced number concentrations and size distributions of submicron particles. The highest and lowest accumulation-mode particle number concentrations were observed in air masses from the YRD and coastal regions, respectively. Continental air masses from inland brought the highest concentrations of nucleation-mode particles. New particle formation (NPF) events, apparent in 44% of the effective measurement days, occurred frequently in all the seasons except winter. The frequency of NPF in spring, summer and autumn is much higher than other measurement sites in China. Sulfuric acid was found to be the main driver of NPF events. The particle formation rate was the highest in spring (3.6 +/- 2.4 cm(-3) s(-1)), whereas the particle growth rate had the highest values in summer (12.8 +/- 4.4 nm h(-1)). The formation rate was typically high in relatively clean air masses, whereas the growth rate tended to be high in the polluted YRD air masses. The frequency of NPF events and the particle growth rates showed a strong year-to-year difference. In the summer of 2013, associated with a multi-week heat wave and strong photochemical processes, NPF events occurred with larger frequency and higher growth rates compared with the same period in 2012. The difference in the location and strength of the subtropical high pressure system, which influences the air mass transport pathways and solar radiation, seems to be the cause for year-to-year differences. This study reports, up to now, the longest continuous measurement records of submicron particles in eastern China and helps to achieve a comprehensive understanding of the main factors controlling the seasonal and year-to-year variation of the aerosol size distribution and NPF in this region.
  • Yli-Juuti, Taina; Tikkanen, Olli-Pekka; Manninen, Hanna E.; Nieminen, Tuomo; Kulmala, Markku (2016)
    We analyzed nanoparticle growth during new-particle-formation events based on ten years of measurements carried out at a boreal forest site in Hyytiala, Finland, concentrating on the sub-3 nm particles and the role of sulfuric acid in their growth. Growth rates of 1.5-3 nm diameter particles were determined from ion spectrometer measurements and compared with parameterized sulfuric acid concentration and other atmospheric parameters. The calculated growth rates from sulfuric acid condensation were on average 7.4% of the observed growth rates and the two did not correlate. These suggest that neither sulfuric acid monomer condensation nor coagulation of small sulfuric acid clusters was the primary growth mechanism in these atmospheric conditions. Also no clear sign of organic condensation being the single main growth mechanism was seen. These observations are consistent with the hypothesis that several factors have comparative roles in the sub-3 nm growth.
  • Buenrostro Mazon, S.; Riipinen, I.; Schultz, D. M.; Valtanen, M.; Dal Maso, M.; Sogacheva, L.; Junninen, H.; Nieminen, T.; Kerminen, V. -M.; Kulmala, M. (2009)
  • Ylivinkka, Ilona; Kaupinmäki, Santeri; Virman, Meri; Peltola, Maija; Taipale, Ditte; Petäjä, Tuukka; Kerminen, Veli-Matti; Kulmala, Markku; Ezhova, Ekaterina (2020)
    We developed a simple algorithm to classify clouds based on global radiation and cloud base height measured by pyranometer and ceilometer, respectively. We separated clouds into seven different classes (stratus, stratocumulus, cumulus, nimbostratus, altocumulus + altostratus, cirrus + cirrocumulus + cirrostratus and clear sky + cirrus). We also included classes for cumulus and cirrus clouds causing global radiation enhancement, and we classified multilayered clouds, when captured by the ceilometer, based on their height and characteristics (transmittance, patchiness and uniformity). The overall performance of the algorithm was nearly 70% when compared with classification by an observer using total-sky images. The performance was best for clouds having well-distinguishable effects on solar radiation: nimbostratus clouds were classified correctly in 100% of the cases. The worst performance corresponds to cirriform clouds (50 %). Although the overall performance of the algorithm was good, it is likely to miss the occurrences of high and multilayered clouds. This is due to the technical limits of the instrumentation: the vertical detection range of the ceilometer and occultation of the laser pulse by the lowest cloud layer. We examined the use of clearness index, which is defined as a ratio between measured global radiation and modeled radiation at the top of the atmosphere, as an indicator of clear-sky conditions. Our results show that cumulus, altocumulus, altostratus and cirriform clouds can be present when the index indicates clear-sky conditions. Those conditions have previously been associated with enhanced aerosol formation under clear skies. This is an important finding especially in the case of low clouds coupled to the surface, which can influence aerosol population via aerosol-cloud interactions. Overall, caution is required when the clearness index is used in the analysis of processes affected by partitioning of radiation by clouds.
  • Paasonen, Pauli; Peltola, Maija; Kontkanen, Jenni; Junninen, Heikki; Kerminen, Veli-Matti; Kulmala, Markku (2018)
    Growth of aerosol particles to sizes at which they can act as cloud condensation nuclei (CCN) is a crucial factor in estimating the current and future impacts of aerosol-cloud-climate interactions. Growth rates (GRs) are typically determined for particles with diameters (d(P)) smaller than 40 nm immediately after a regional new particle formation (NPF) event. These growth rates are often taken as representatives for the particle growth to CCN sizes (d(P) > 50-100 nm). In modelling frameworks, the concentration of the condensable vapours causing the growth is typically calculated with steady state assumptions, where the condensation sink (CS) is the only loss term for the vapours. Additionally, the growth to CCN sizes is represented with the condensation of extremely low-volatility vapours and gas-particle partitioning of semi-volatile vapours. Here, we use a novel automatic method to determine growth rates from below 10 nm to hundreds of nanometres from a 20-year-long particle size distribution (PSD) data set in boreal forest. With this method, we are able to detect growth rates also at times other than immediately after a NPF event. We show that the GR increases with an increasing oxidation rate of monoterpenes, which is closely coupled with the ambient temperature. Based on our analysis, the oxidation reactions of monoterpenes with ozone, hydroxyl radical and nitrate radical all are capable of producing vapours that contribute to the particle growth in the studied size ranges. We find that GR increases with particle diameter, resulting in up to 3-fold increases in GRs for particles with d(P) similar to 100 nm in comparison to those with d(P) similar to 10 nm. We use a single particle model to show that this increase in GR can be explained with aerosol-phase reactions, in which semi-volatile vapours form non-volatile dimers. Finally, our analysis reveals that the GR of particles with d(P) <100 nm is not limited by the condensation sink, even though the GR of larger particles is. Our findings suggest that in the boreal continental environment, the formation of CCN from NPF or sub-100 nm emissions is more effective than previously thought and that the formation of CCN is not as strongly self-limiting a process as the previous estimates have suggested.
  • Fanourgakis, George S.; Kanakidou, Maria; Nenes, Athanasios; Bauer, Susanne E.; Bergman, Tommi; Carslaw, Ken S.; Grini, Alf; Hamilton, Douglas S.; Johnson, Jill S.; Karydis, Vlassis A.; Kirkevag, Alf; Kodros, John K.; Lohmann, Ulrike; Luo, Gan; Makkonen, Risto; Matsui, Hitoshi; Neubauer, David; Pierce, Jeffrey R.; Schmale, Julia; Stier, Philip; Tsigaridis, Kostas; van Noije, Twan; Wang, Hailong; Watson-Parris, Duncan; Westervelt, Daniel M.; Yang, Yang; Yoshioka, Masaru; Daskalakis, Nikos; Decesari, Stefano; Gysel-Beer, Martin; Kalivitis, Nikos; Liu, Xiaohong; Mahowald, Natalie M.; Myriokefalitakis, Stelios; Schrodner, Roland; Sfakianaki, Maria; Tsimpidi, Alexandra P.; Wu, Mingxuan; Yu, Fangqun (2019)
    A total of 16 global chemistry transport models and general circulation models have participated in this study; 14 models have been evaluated with regard to their ability to reproduce the near-surface observed number concentration of aerosol particles and cloud condensation nuclei (CCN), as well as derived cloud droplet number concentration (CDNC). Model results for the period 2011-2015 are compared with aerosol measurements (aerosol particle number, CCN and aerosol particle composition in the submicron fraction) from nine surface stations located in Europe and Japan. The evaluation focuses on the ability of models to simulate the average across time state in diverse environments and on the seasonal and short-term variability in the aerosol properties. There is no single model that systematically performs best across all environments represented by the observations. Models tend to underestimate the observed aerosol particle and CCN number concentrations, with average normalized mean bias (NMB) of all models and for all stations, where data are available, of -24 % and -35 % for particles with dry diameters > 50 and > 120 nm, as well as -36 % and -34 % for CCN at supersaturations of 0.2 % and 1.0 %, respectively. However, they seem to behave differently for particles activating at very low supersaturations (<0.1 %) than at higher ones. A total of 15 models have been used to produce ensemble annual median distributions of relevant parameters. The model diversity (defined as the ratio of standard deviation to mean) is up to about 3 for simulated N-3 (number concentration of particles with dry diameters larger than 3 nm) and up to about 1 for simulated CCN in the extra-polar regions. A global mean reduction of a factor of about 2 is found in the model diversity for CCN at a supersaturation of 0.2 % (CCN0.2) compared to that for N-3, maximizing over regions where new particle formation is important. An additional model has been used to investigate potential causes of model diversity in CCN and bias compared to the observations by performing a perturbed parameter ensemble (PPE) accounting for uncertainties in 26 aerosol-related model input parameters. This PPE suggests that biogenic secondary organic aerosol formation and the hygroscopic properties of the organic material are likely to be the major sources of CCN uncertainty in summer, with dry deposition and cloud processing being dominant in winter. Models capture the relative amplitude of the seasonal variability of the aerosol particle number concentration for all studied particle sizes with available observations (dry diameters larger than 50, 80 and 120 nm). The short-term persistence time (on the order of a few days) of CCN concentrations, which is a measure of aerosol dynamic behavior in the models, is underestimated on average by the models by 40 % during winter and 20 % in summer. In contrast to the large spread in simulated aerosol particle and CCN number concentrations, the CDNC derived from simulated CCN spectra is less diverse and in better agreement with CDNC estimates consistently derived from the observations (average NMB -13 % and -22 % for updraft velocities 0.3 and 0.6 m s(-1), respectively). In addition, simulated CDNC is in slightly better agreement with observationally derived values at lower than at higher updraft velocities (index of agreement 0.64 vs. 0.65). The reduced spread of CDNC compared to that of CCN is attributed to the sublinear response of CDNC to aerosol particle number variations and the negative correlation between the sensitivities of CDNC to aerosol particle number concentration (partial derivative N-d/partial derivative N-a) and to updraft velocity (partial derivative N-d/partial derivative w). Overall, we find that while CCN is controlled by both aerosol particle number and composition, CDNC is sensitive to CCN at low and moderate CCN concentrations and to the updraft velocity when CCN levels are high. Discrepancies are found in sensitivities partial derivative N-d/partial derivative N-a and partial derivative N-d/partial derivative w; models may be predisposed to be too "aerosol sensitive" or "aerosol insensitive" in aerosol-cloud-climate interaction studies, even if they may capture average droplet numbers well. This is a subtle but profound finding that only the sensitivities can clearly reveal and may explain intermodel biases on the aerosol indirect effect.
  • Sahyoun, Maher; Freney, Evelyn; Brito, Joel; Duplissy, Jonathan; Gouhier, Mathieu; Colomb, Aurélie; Dupuy, Regis; Bourianne, Thierry; Nowak, John B.; Yan, Chao; Petäjä, Tuukka; Kulmala, Markku; Schwarzenboeck, Alfons; Planche, Céline; Sellegri, Karine (2019)
    Abstract Volcanic emissions can significantly affect the Earth's radiation budget by emitting aerosol particles and gas-phase species that can result in the new particle formation (NPF). These particles can scatter solar radiation or modify cloud properties, with consequences on health, weather, and climate. To our knowledge, this is the first dedicated study detailing how gas-phase precursors emitted from volcanic plumes can influence the NPF. A series of airborne measurements were performed around the Etna and Stromboli volcanoes within the framework of the CLerVolc and STRAP projects. The ATR-42 aircraft was equipped with a range of instrumentation allowing the measurement of particle number concentration in diameter range above 2.5 nm, and gaseous species to investigate the aerosol dynamics and the processes governing the NPF and their growth within the volcanic plumes. We demonstrate that NPF occurs within the volcanic plumes in the Free Troposphere (FT) and Boundary Layer (BL). Typically, the NPF events were more pronounced in the FT, where the condensational sink was up to two orders of magnitude smaller and the temperature was ~20°C lower than in the BL. Within the passive volcanic plume, the concentration of sulfur dioxide, sulfuric acid, and N2.5 were as high as 92 ppbV, 5.65?108 and 2.4?105 cm?3, respectively. Using these measurements, we propose a new parameterization for NPF rate (J2.5) within the passive volcanic plume in the FT. These results can be incorporated into mesoscale models to better assess the impact of the particle formed by natural processes, i.e. volcanic plumes, on climate.
  • Dada, Lubna; Lehtipalo, Katrianne; Kontkanen, Jenni; Nieminen, Tuomo; Baalbaki, Rima; Ahonen, Lauri; Duplissy, Jonathan; Yan, Chao; Chu, Biwu; Petäjä, Tuukka; Lehtinen, Kari; Kerminen, Veli-Matti; Kulmala, Markku; Kangasluoma, Juha (2020)
    Atmospheric new particle formation (NPF), which is observed in many environments globally, is an important source of boundary-layer aerosol particles and cloud condensation nuclei, which affect both the climate and human health. To better understand the mechanisms behind NPF, chamber experiments can be used to simulate this phenomenon under well-controlled conditions. Recent advancements in instrumentation have made it possible to directly detect the first steps of NPF of molecular clusters (similar to 1-2 nm in diameter) and to calculate quantities such as the formation and growth rates of these clusters. Whereas previous studies reported particle formation rates as the flux of particles across a specified particle diameter or calculated them from measurements of larger particle sizes, this protocol outlines methods to directly quantify particle dynamics for cluster sizes. Here, we describe the instrumentation and analysis methods needed to quantify particle dynamics during NPF of sub-3-nm aerosol particles in chamber experiments. The methods described in this protocol can be used to make results from different chamber experiments comparable. The experimental setup, collection and post-processing of the data, and thus completion of this protocol, take from months up to years, depending on the chamber facility, experimental plan and level of expertise. Use of this protocol requires engineering capabilities and expertise in data analysis.
  • Nieminen, Tuomo; Kerminen, Veli-Matti; Petäjä, Tuukka; Aalto, Pasi P.; Arshinov, Mikhail; Asmi, Eija; Baltensperger, Urs; Beddows, David C. S.; Beukes, Johan Paul; Collins, Don; Ding, Aijun; Harrison, Roy M.; Henzing, Bas; Hooda, Rakesh; Hu, Min; Horrak, Urmas; Kivekäs, Niku; Komsaare, Kaupo; Krejci, Radovan; Kristensson, Adam; Laakso, Lauri; Laaksonen, Ari; Leaitch, W. Richard; Lihavainen, Heikki; Mihalopoulos, Nikolaos; Nemeth, Zoltan; Nie, Wei; O'Dowd, Colin; Salma, Imre; Sellegri, Karine; Svenningsson, Birgitta; Swietlicki, Erik; Tunved, Peter; Ulevicius, Vidmantas; Vakkari, Ville; Vana, Marko; Wiedensohler, Alfred; Wu, Zhijun; Virtanen, Annele; Kulmala, Markku (2018)
    Atmospheric new particle formation (NPF) is an important phenomenon in terms of global particle number concentrations. Here we investigated the frequency of NPF, formation rates of 10 nm particles, and growth rates in the size range of 10-25 nm using at least 1 year of aerosol number size-distribution observations at 36 different locations around the world. The majority of these measurement sites are in the Northern Hemisphere. We found that the NPF frequency has a strong seasonal variability. At the measurement sites analyzed in this study, NPF occurs most frequently in March-May (on about 30 % of the days) and least frequently in December-February (about 10 % of the days). The median formation rate of 10 nm particles varies by about 3 orders of magnitude (0.01-10 cm(-3) s(-1)) and the growth rate by about an order of magnitude (1-10 nm h(-1)). The smallest values of both formation and growth rates were observed at polar sites and the largest ones in urban environments or anthropogenically influenced rural sites. The correlation between the NPF event frequency and the particle formation and growth rate was at best moderate among the different measurement sites, as well as among the sites belonging to a certain environmental regime. For a better understanding of atmospheric NPF and its regional importance, we would need more observational data from different urban areas in practically all parts of the world, from additional remote and rural locations in North America, Asia, and most of the Southern Hemisphere (especially Australia), from polar areas, and from at least a few locations over the oceans.
  • 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.
  • Manninen, Hanna E.; Mirme, Sander; Mirme, Aadu; Petäjä, Tuukka; Kulmala, Markku (2016)
    To understand the very first steps of atmospheric particle formation and growth processes, information on the size where the atmospheric nucleation and cluster activation occurs, is crucially needed. The current understanding of the concentrations and dynamics of charged and neutral clusters and particles is based on theoretical predictions and experimental observations. This paper gives a standard operation procedure (SOP) for Neutral cluster and Air Ion Spectrometer (NAIS) measurements and data processing. With the NAIS data, we have improved the scientific understanding by (1) direct detection of freshly formed atmospheric clusters and particles, (2) linking experimental observations and theoretical framework to understand the formation and growth mechanisms of aerosol particles, and (3) parameterizing formation and growth mechanisms for atmospheric models. The SOP provides tools to harmonize the world-wide measurements of small clusters and nucleation mode particles and to verify consistent results measured by the NAIS users. The work is based on discussions and interactions between the NAIS users and the NAIS manufacturer.
  • Ylivinkka, Ilona; Itämies, Juhani; Klemola, Tero; Ruohomäki, Kai; Kulmala, Markku; Taipale, Ditte (2020)
    Laboratory studies have shown that heibivory-induced biogenic volatile organic compound (BVOC) emissions might enhance aerosol formation and growth. To increase understanding of the atmospheric relevance of this enhancement, we analyzed 25 years of data from SMEAR I (Station for Measuring Ecosystem-Atmosphere Relations) in northern Finland, where autumnal moth (Epirrita autumnata) larvae are prominent defoliators of mountain birch. We did not find a direct correlation between the autumnal moth density and aerosol processes, nor between the total number concentration and temperature, and hence the basal BVOC emissions. Instead, there is some evidence that the total particle concentration is elevated even for a few years after the infestation due to delayed defense response of mountain birch. The low total biomass of the trees concomitantly with low autumnal moth densities during most of the years of our study, may have impacted our results, hindering the enhancement of aerosol processes.
  • Tuovinen, Saana; Kontkanen, Jenni; Jiang, Jingkun; Kulmala, Markku (2020)
    New Particle Formation (NPF) is regularly observed to occur in heavily polluted Chinese megacities. However, in these NPF events, the survival probability of small clusters into larger aerosol particles is higher than theoretically predicted. One explanation for this could be that the loss rate of clusters due to scavenging by pre-existing particles, which is described by condensation sink, is lower than expected. In this study, we describe the loss of clusters due to condensation sink by using heterogeneous nucleation theory, and investigate if ineffectiveness of heterogeneous nucleation can result in a significantly lowered effective condensation sink. We find that in principle it is possible that due to properties of the system there is no heterogeneous nucleation, and this can significantly influence the magnitude of effective condensation sink and thus increase the survival probability of clusters.
  • Pirjola, L.; Karl, M.; Rönkkö, T.; Arnold, F. (2015)
    A high concentration of volatile nucleation mode particles (NUP) formed in the atmosphere when the exhaust cools and dilutes has hazardous health effects and it impairs the visibility in urban areas. Nucleation mechanisms in diesel exhaust are only poorly understood. We performed model studies using two sectional aerosol dynamics process models AEROFOR and MAFOR on the formation of particles in the exhaust of a diesel engine, equipped with an oxidative after-treatment system and running with low fuel sulfur content (FSC) fuel, under laboratory sampling conditions where the dilution system mimics real-world conditions. Different nucleation mechanisms were tested. Based on the measured gaseous sulfuric acid (GSA) and non-volatile core and soot particle number concentrations of the raw exhaust, the model simulations showed that the best agreement between model predictions and measurements in terms of particle number size distribution was obtained by barrier-free heteromolecular homogeneous nucleation between the GSA and a semi-volatile organic vapour combined with the homogeneous nucleation of GSA alone. Major growth of the particles was predicted to occur due to the similar organic vapour at concentrations of (1-2) x 10(12) cm(-3). The pre-existing core and soot mode concentrations had an opposite trend on the NUP formation, and the maximum NUP formation was predicted if a diesel particle filter (DPF) was used. On the other hand, the model predicted that the NUP formation ceased if the GSA concentration in the raw exhaust was less than 10(10) cm(-3), which was the case when biofuel was used.
  • Peräkylä, Otso; Vogt, Matthias; Tikkanen, Olli-Pekka; Laurila, Terhi; Kajos, Maija K.; Rantala, Pekka A.; Patokoski, Johanna; Aalto, Juho; Yli-Juuti, Taina; Ehn, Mikael; Sipila, Mikko; Paasonen, Pauli; Rissanen, Matti; Nieminen, Tuomo; Taipale, Risto; Keronen, Petri; Lappalainen, Hanna K.; Ruuskanen, Taina M.; Rinne, Janne; Kerminen, Veli-Matti; Kulmala, Markku; Back, Jaana; Petaja, Tuukka (2014)
  • Määttänen, Anni; Merikanto, Joonas; Henschel, Henning; Duplissy, Jonathan; Makkonen, Risto; Ortega, Ismael K.; Vehkamäki, Hanna (2018)
    We have developed new parameterizations of electrically neutral homogeneous and ion-induced sulfuric acid-water particle formation for large ranges of environmental conditions, based on an improved model that has been validated against a particle formation rate data set produced by Cosmics Leaving OUtdoor Droplets (CLOUD) experiments at European Organization for Nuclear Research (CERN). The model uses a thermodynamically consistent version of the Classical Nucleation Theory normalized using quantum chemical data. Unlike the earlier parameterizations for H2SO4-H2O nucleation, the model is applicable to extreme dry conditions where the one-component sulfuric acid limit is approached. Parameterizations are presented for the critical cluster sulfuric acid mole fraction, the critical cluster radius, the total number of molecules in the critical cluster, and the particle formation rate. If the critical cluster contains only one sulfuric acid molecule, a simple formula for kinetic particle formation can be used: this threshold has also been parameterized. The parameterization for electrically neutral particle formation is valid for the following ranges: temperatures 165-400K, sulfuric acid concentrations 10(4)-10(13)cm(-3), and relative humidities 0.001-100%. The ion-induced particle formation parameterization is valid for temperatures 195-400K, sulfuric acid concentrations 10(4)-10(16)cm(-3), and relative humidities 10(-5)-100%. The new parameterizations are thus applicable for the full range of conditions in the Earth's atmosphere relevant for binary sulfuric acid-water particle formation, including both tropospheric and stratospheric conditions. They are also suitable for describing particle formation in the atmosphere of Venus.
  • Dall'Osto, M.; Beddows, D. C. S.; Asmi, A.; Poulain, L.; Hao, L.; Freney, E.; Allan, J. D.; Canagaratna, M.; Crippa, M.; Bianchi, F.; de Leeuw, G.; Eriksson, A.; Swietlicki, E.; Hansson, H. C.; Henzing, J. S.; Granier, C.; Zemankova, K.; Laj, P.; Onasch, T.; Prevot, A.; Putaud, J. P.; Sellegri, K.; Vidal, M.; Virtanen, A.; Simo, R.; Worsnop, D.; O'Dowd, C.; Kulmala, M.; Harrison, Roy M. (2018)
    The formation of new atmospheric particles involves an initial step forming stable clusters less than a nanometre in size (similar to 10 nm). Although at times, the same species can be responsible for both processes, it is thought that more generally each step comprises differing chemical contributors. Here, we present a novel analysis of measurements from a unique multi-station ground-based observing system which reveals new insights into continental-scale patterns associated with new particle formation. Statistical cluster analysis of this unique 2-year multi-station dataset comprising size distribution and chemical composition reveals that across Europe, there are different major seasonal trends depending on geographical location, concomitant with diversity in nucleating species while it seems that the growth phase is dominated by organic aerosol formation. The diversity and seasonality of these events requires an advanced observing system to elucidate the key processes and species driving particle formation, along with detecting continental scale changes in aerosol formation into the future.
  • Schobesberger, S.; Franchin, A.; Bianchi, F.; Rondo, L.; Duplissy, J.; Kuerten, A.; Ortega Colomer, Ismael Kenneth; Metzger, A.; Schnitzhofer, R.; Almeida, J.; Amorim, A.; Dommen, J.; Dunne, E. M.; Ehn, M.; Gagne, S.; Ickes, L.; Junninen, H.; Hansel, A.; Kerminen, V-M; Kirkby, J.; Kupc, A.; Laaksonen, A.; Lehtipalo, K.; Mathot, S.; Onnela, A.; Petaja, T.; Riccobono, F.; Santos, F. D.; Sipila, M.; Tome, A.; Tsagkogeorgas, G.; Viisanen, Y.; Wagner, P. E.; Wimmer, D.; Curtius, J.; Donahue, N. M.; Baltensperger, U.; Kulmala, M.; Worsnop, D. R. (2015)
  • Kulmala, Markku; Luoma, Krista; Virkkula, Aki; Petäjä, Tuukka; Paasonen, Pauli; Kerminen, Veli-Matti; Nie, Wei; Qi, Ximeng; Shen, Yicheng; Chi, Xuguang; Ding, Aijun (2016)
    Aerosol particle concentrations in the atmosphere are governed by their sources and sinks. Sources include directly-emitted (primary) and secondary aerosol particles formed from gas-phase precursor compounds. The relative importance of primary and secondary aerosol particles varies regionally and with time. In this work, we investigated primary and secondary contributions to mode-segregated particle number concentrations by using black carbon as a tracer for the primary aerosol number concentration. We studied separately nucleation, Aitken and accumulation mode concentrations at a rural boreal forest site (Hyytiala, Finland) and in a rather polluted megacity environment (Nanjing, China) using observational data from 2011 to 2014. In both places and in all the modes, the majority of particles were estimated to be of secondary origin. Even in Nanjing, only about half of the accumulation mode particles were estimated to be of primary origin. Secondary particles dominated particularly in the nucleation and Aitken modes.