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  • Groess, Johannes; Hamed, Amar; Sonntag, Andre; Spindler, Gerald; Manninen, Hanna Elina; Nieminen, Tuomo; Kulmala, Markku; Horrak, Urmas; Plass-Dülmer, Christian; Wiedensohler, Alfred; Birmili, Wolfram (2018)
    This paper revisits the atmospheric new particle formation (NPF) process in the polluted Central European troposphere, focusing on the connection with gas-phase precursors and meteorological parameters. Observations were made at the research station Melpitz (former East Germany) between 2008 and 2011 involving a neutral cluster and air ion spectrometer (NAIS). Particle formation events were classified by a new automated method based on the convolution integral of particle number concentration in the diameter interval 2-20 nm. To study the relevance of gaseous sulfuric acid as a precursor for nucleation, a proxy was derived on the basis of direct measurements during a 1-month campaign in May 2008. As a major result, the number concentration of freshly produced particles correlated significantly with the concentration of sulfur dioxide as the main precursor of sulfuric acid. The condensation sink, a factor potentially inhibiting NPF events, played a subordinate role only. The same held for experimentally determined ammonia concentrations. The analysis of meteorological parameters confirmed the absolute need for solar radiation to induce NPF events and demonstrated the presence of significant turbu-lence during those events. Due to its tight correlation with solar radiation, however, an independent effect of turbulence for NPF could not be established. Based on the diurnal evolution of aerosol, gas-phase, and meteorological parameters near the ground, we further conclude that the particle formation process is likely to start in elevated parts of the boundary layer rather than near ground level.
  • Chen, Xuemeng; Virkkula, Aki; Kerminen, Veli-Matti; Manninen, Hanna E.; Busetto, Maurizio; Lanconelli, Christian; Lupi, Angelo; Vitale, Vito; Del Guasta, Massimo; Grigioni, Paolo; Väänänen, Riikka; Duplissy, Ella-Maria; Petäjä, Tuukka; Kulmala, Markku (2017)
    An air ion spectrometer (AIS) was deployed for the first time at the Concordia station at Dome C (75 degrees 06'S, 123 degrees 23'E; 3220 ma.s.l.), Antarctica during the period 22 December 2010-16 November 2011 for measuring the number size distribution of air ions. In this work, we present results obtained from this air ion data set together with aerosol particle and meteorological data. The main processes that modify the number size distribution of air ions during the measurement period at this high-altitude site included new particle formation (NPF, observed on 85 days), wind-induced ion formation (observed on 36 days), and ion production and loss associated with cloud/fog formation (observed on 2 days). For the subset of days when none of these processes seemed to operate, the concentrations of cluster ions (0.9-1.9 nm) exhibited a clear seasonality, with high concentrations in the warm months and low concentrations in the cold. Compared to event-free days, days with NPF were observed with higher cluster ion concentrations. A number of NPF events were observed with restricted growth below 10 nm, which were termed as suppressed NPF. There was another distinct feature, namely a simultaneous presence of two or three separate NPF and subsequent growth events, which were named as multi-mode NPF events. Growth rates (GRs) were determined using two methods: the appearance time method and the mode fitting method. The former method seemed to have advantages in characterizing NPF events with a fast GR, whereas the latter method is more suitable when the GR was slow. The formation rate of 2 nm positive ions (J(2)(+)) was calculated for all the NPF events for which a GR in the 2-3 nm size range could be determined. On average, J(2)(+) was about 0.014 cm(-3) s(-1). The ion production in relation to cloud/fog formation in the size range of 8-42 nm seemed to be a unique feature at Dome C, which has not been reported elsewhere. These ions may, however, either be multiply charged particles but detected as singly charged in the AIS, or be produced inside the instrument, due to the breakage of cloud condensation nuclei (CCN), possibly related to the instrumental behaviour under the extremely cold condition. For the wind-induced ion formation, our observations suggest that the ions originated more likely from atmospheric nucleation of vapours released from the snow than from mechanical charging of shattered snow flakes and ice crystals.
  • Leino, Katri; Nieminen, Tuomo; Manninen, Hanna E.; Petäjä, Tuukka; Kerminen, Veli-Matti; Kulmala, Markku (2016)
    Secondary aerosol formation from gas-phase precursors is a frequent phenomenon occurring in a boreal environment. Traditionally, this process is identified visually from observational data on total and ion number size distributions. Here, we introduce a new, objective classification method for the new particle formation events based on measured intermediate-ion concentrations. The intermediate-ion concentration is a suitable indicator of new particle formation, because it is linked to the atmospheric new particle formation. The concentration of intermediate ions is typically very low (below 5 cm(-3)) when there is no new particle formation or precipitation events occurring. In this study, we analysed concentrations of negative intermediate ions at the Station for Measuring Ecosystem Atmosphere Relations (SMEAR II) in Hyytiala, Finland, during the years 2003-2013. We found that the half-hour median concentration of negative intermediate ions in sizes 2-4 nm was > 20 cm(-3) during 77.5% of event days classified by traditional method. The corresponding value was 92.3% in the case of 2-7 nm negative ions. In addition, the intermediate-ion concentration varied seasonally in a similar manner as the number of event days, peaking in the spring. A typical diurnal variation of the intermediate-ion concentration resembled that of the particle concentration during the event days. We developed here a new method for classifying new particle formation events based on intermediate-ion concentrations. The new method is complementary to the traditional event analysis and it can also be used as an automatic way of determining new particle formation events from large data sets.
  • Cai, Runlong; Jiang, Jingkun; Mirme, Sander; Kangasluoma, Juha (2019)
    Measuring aerosol size distributions accurately down to similar to 1 nm is a key to nucleation studies, and it requires developments and improvements in instruments such as electrical mobility spectrometers in use today. The key factors characterizing the performance of an electrical mobility spectrometer for sub-3 nm particles are discussed in this study. A parameter named as Pi is proposed as a figure of merit for the performance of an electrical mobility spectrometer in the sub-3 nm size range instead of the overall detection efficiency. Pi includes the overall detection efficiency, the measurement time in each size bin, the aerosol flow rate passing through the detector, and the aerosol-to-sheath flow ratio of the differential mobility analyzer. The particle raw count number recorded by the detector can be estimated using Pi at a given aerosol size distribution function, dN/dlogd(p)( ). The limit of detection for the spectrometer and the statistical uncertainty of the measured aerosol size distribution can also be readily estimated using Pi. In addition to Pi, the size resolution of an electrical mobility analyzer is another factor characterizing the systematic errors originated from particle sizing. Four existing electrical mobility spectrometers designed for measuring sub-3 nm aerosol size distributions, including three scanning/differential mobility particle spectrometers and one differential mobility analyzer train, are examined. Their optimal performance is evaluated using Pi and the size resolution. For example, the Pi value and the size resolution of a diethylene-glycol differential mobility particle spectrometer for 1.5 nm particles are 8.0 x 10(-4) cm(3) and 5.7, respectively. The corresponding relative uncertainty of the measured size distribution is approximately 9.6% during an atmospheric new particle formation event with a dN/dlogd(p) of 5 x 10(5) cm(-3) . Assuming an adjustable sheath flow rate of the differential mobility analyzer, the optimal size resolution is approximately 5-9 when measuring atmospheric new particle formation events.
  • Kangasluoma, Juha; Attoui, Michael (2019)
    This review discusses the developments in aerosol instrumentation that have led to the current vapor condensation based instruments capable of detecting sub-3 nm particles. We begin from selected reports prior to the year 1991, which have advanced the technology or understanding in condensation particle counting toward sub-3 nm sizes, and continue to more in depth review of the past efforts after 1991. We discuss how the developments in the calibration methods have progressed the development of particle counting techniques, and review briefly the sub-3 nm calibration experiments and cluster production methods used in calibration experiments. Based on these reviews, we identify several technological and scientific advances for the future to improve the accuracy, understanding, and technology of sub-3 nm particle counting. Copyright (c) 2019 American Association for Aerosol Research
  • Yan, Chao; Yin, Rujing; Lu, Yiqun; Dada, Lubna; Yang, Dongsen; Fu, Yueyun; Kontkanen, Jenni; Deng, Chenjuan; Garmash, Olga; Ruan, Jiaxin; Baalbaki, Rima; Schervish, Meredith; Cai, Runlong; Bloss, Matthew; Chan, Tommy; Chen, Tianzeng; Chen, Qi; Chen, Xuemeng; Chen, Yan; Chu, Biwu; Dällenbach, Kaspar; Foreback, Benjamin; He, Xucheng; Heikkinen, Liine; Jokinen, Tuija; Junninen, Heikki; Kangasluoma, Juha; Kokkonen, Tom; Kurppa, Mona; Lehtipalo, Katrianne; Li, Haiyan; Li, Hui; Li, Xiaoxiao; Liu, Yiliang; Ma, Qingxin; Paasonen, Pauli; Rantala, Pekka; Pileci, Rosaria E.; Rusanen, Anton; Sarnela, Nina; Simonen, Pauli; Wang, Shixian; Wang, Weigang; Wang, Yonghong; Xue, Mo; Yang, Gan; Yao, Lei; Zhou, Ying; Kujansuu, Joni; Petäjä, Tuukka; Nie, Wei; Ma, Yan; Ge, Maofa; He, Hong; Donahue, Neil M.; Worsnop, Douglas R.; Kerminen, Veli-Matti; Wang, Lin; Liu, Yongchun; Zheng, Jun; Kulmala, Markku; Jiang, Jingkun; Bianchi, Federico (2021)
    Intense and frequent new particle formation (NPF) events have been observed in polluted urban environments, yet the dominant mechanisms are still under debate. To understand the key species and governing processes of NPF in polluted urban environments, we conducted comprehensive measurements in downtown Beijing during January-March, 2018. We performed detailed analyses on sulfuric acid cluster composition and budget, as well as the chemical and physical properties of oxidized organic molecules (OOMs). Our results demonstrate that the fast clustering of sulfuric acid (H2SO4) and base molecules triggered the NPF events, and OOMs further helped grow the newly formed particles toward climate- and health-relevant sizes. This synergistic role of H2SO4, base species, and OOMs in NPF is likely representative of polluted urban environments where abundant H2SO4 and base species usually co-exist, and OOMs are with moderately low volatility when produced under high NOx concentrations.
  • de Jesus, Alma Lorelei; Rahman, Md Mahmudur; Mazaheri, Mandana; Thompson, Helen; Knibbs, Luke D.; Jeong, Cheol; Evans, Greg; Nei, Wei; Ding, Aijun; Qiao, Liping; Li, Li; Portin, Harri; Niemi, Jarkko V.; Timonen, Hilkka; Luoma, Krista; Petäjä, Tuukka; Kulmala, Markku; Kowalski, Michal; Peters, Annette; Cyrys, Josef; Ferrero, Luca; Manigrasso, Maurizio; Avino, Pasquale; Buonano, Giorgio; Reche, Cristina; Querol, Xavier; Beddows, David; Harrison, Roy M.; Sowlat, Mohammad H.; Sioutas, Constantinos; Morawska, Lidia (2019)
    Can mitigating only particle mass, as the existing air quality measures do, ultimately lead to reduction in ultrafine particles (UFP)? The aim of this study was to provide a broader urban perspective on the relationship between UFP, measured in terms of particle number concentration (PNC) and PM2.5 (mass concentration of particles with aerodynamic diameter <2.5 mu m) and factors that influence their concentrations. Hourly average PNC and PM2.5 were acquired from 10 cities located in North America, Europe, Asia, and Australia over a 12-month period. A pairwise comparison of the mean difference and the Kolmogorov-Smirnov test with the application of bootstrapping were performed for each city. Diurnal and seasonal trends were obtained using a generalized additive model (GAM). The particle number to mass concentration ratios and the Pearson's correlation coefficient were calculated to elucidate the nature of the relationship between these two metrics. Results show that the annual mean concentrations ranged from 8.0 x 10 3 to 19.5 x 10(3) and from 7.0 to 65.8 mu g.m(-3) for PNC and PM2.5, respectively, with the data distributions generally skewed to the right, and with a wider spread for PNC. PNC showed a more distinct diurnal trend compared with PM2.5, attributed to the high contributions of UFP from vehicular emissions to PNC. The variation in both PNC and PM2.5 due to seasonality is linked to the cities' geographical location and features. Clustering the cities based on annual median concentrations of both PNC and PM2.5 demonstrated that a high PNC level does not lead to a high PM2.5, and vice versa. The particle number-to-mass ratio (in units of 10(9) g(-1)) ranged from 0.14 to 2.2, > 1 for roadside sites and <1 for urban background sites with lower values for more polluted cities. The Pearson's r ranged from 0.09 to 0.64 for the log-transformed data, indicating generally poor linear correlation between PNC and PM2.5. Therefore, PNC and PM2.5 measurements are not representative of each other; and regulating PM2.5 does little to reduce PNC. This highlights the need to establish regulatory approaches and control measures to address the impacts of elevated UFP concentrations, especially in urban areas, considering their potential health risks.
  • Carnerero, Cristina; Perez, Noemi; Reche, Cristina; Ealo, Marina; Titos, Gloria; Lee, Hong-Ku; Eun, Hee-Ram; Park, Yong-Hee; Dada, Lubna; Paasonen, Pauli; Kerminen, Veli-Matti; Mantilla, Enrique; Escudero, Miguel; Gomez-Moreno, Francisco J.; Alonso-Blanco, Elisabeth; Coz, Esther; Saiz-Lopez, Alfonso; Temime-Roussel, Brice; Marchand, Nicolas; Beddows, David C. S.; Harrison, Roy M.; Petäjä, Tuukka; Kulmala, Markku; Ahn, Kang-Ho; Alastuey, Andres; Querol, Xavier (2018)
    The vertical profile of new particle formation (NPF) events was studied by comparing the aerosol size number distributions measured aloft and at surface level in a suburban environment in Madrid, Spain, using airborne instruments. The horizontal distribution and regional impact of the NPF events was investigated with data from three urban, urban background, and suburban stations in the Madrid metropolitan area. Intensive regional NPF episodes followed by particle growth were simultaneously recorded at three stations in and around Madrid during a field campaign in July 2016. The urban stations presented larger formation rates compared to the suburban station. Condensation and coagulation sinks followed a similar evolution at all stations, with higher values at urban stations. However, the total number concentration of particles larger than 2.5 nm was lower at the urban station and peaked around noon, when black carbon (BC) levels are at a minimum. The vertical soundings demonstrated that ultrafine particles (UFPs) are formed exclusively inside the mixed layer. As convection becomes more effective and the mixed layer grows, UFPs are detected at higher levels. The morning soundings revealed the presence of a residual layer in the upper levels in which aged particles (nucleated and grown on previous days) prevail. The particles in this layer also grow in size, with growth rates significantly smaller than those inside the mixed layer. Under conditions with strong enough convection, the soundings revealed homogeneous number size distributions and growth rates at all altitudes, which follow the same evolution at the other stations considered in this study. This indicates that UFPs are detected quasi-homogenously in an area spanning at least 17 km horizontally. The NPF events extend over the full vertical extension of the mixed layer, which can reach as high as 3000 m in the area, according to previous studies. On some days a marked decline in particle size (shrinkage) was observed in the afternoon, associated with a change in air masses. Additionally, a few nocturnal nucleation-mode bursts were observed at the urban stations, for which further research is needed to elucidate their origin.