Browsing by Subject "GROWTH-RATES"

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  • Mazon, Stephany Buenrostro; Kontkanen, Jenni; Manninen, Hanna E.; Nieminen, Tuomo; Kerminen, Veli-Matti; Kulmala, Markku (2016)
    New particle formation (NPF) events are typically observed during daytime when photochemical oxidation takes place. However, nighttime nucleation mode particles have been observed across various locations only sporadically. We present 11 years (2003-2013) of air ion number size distribution data from the SMEAR II station in Hyytiala, Finland, where during a third of the nights a sub-3 nm negative (n = 1324 days) and positive (n = 1174 days) ion events took place. To investigate nocturnal clustering at sizes above the constant small ion pool, we defined cluster events (CE) as a nocturnal event with 2-3 nm ion concentrations reaching 70 cm-3 between 18:00 and 24:00 local time. CE (n = 221 days) were characterized by a rapid, 10-fold increase in the median 2-3 nm ion concentration from the start (similar to 10 cm(-3)) to the event peak (similar to 100 cm(-3)). Furthermore, small and intermediate ions during the CE, NPF events and nonevents were compared: while concentrations of 1.5-2 nm ions were the highest during CE (median 235 cm(-3)), as compared with the NPF events (96 cm(-3)) or the daytime and nighttime nonevents (similar to 20 cm(-3)), 3-7 nm ion concentrations increased notably only during NPF events (median 52 cm(-3)). Specifically, ion concentrations during CE decreased for sizes above-2.4 nm (<10 cm(-3)). In addition, 90% of CE proceeded either a NPF event (55%) or a undefined day (35%), and only 10% of them proceeded a daytime non-event. This study suggests a build-up of 0.9-2.4 nm ion clusters during CE nights (18:00-24:00) that equals or exceeds the ion concentration levels during daytime NPF, but unlike the latter, CE fail to activate and grow clusters > 3 nm in diameter in nighttime Hyytiald.
  • 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.
  • Chan, Tommy; Cai, Runlong; Ahonen, Lauri R.; Liu, Yiliang; Zhou, Ying; Vanhanen, Joonas; Dada, Lubna; Chao, Yan; Liu, Yongchun; Wang, Lin; Kulmala, Markku; Kangasluoma, Juha (2020)
    Accurate measurements of the size distribution of atmospheric aerosol nanoparticles are essential to build an understanding of new particle formation and growth. This is particularly crucial at the sub-3 nm range due to the growth of newly formed nanoparticles. The challenge in recovering the size distribution is due its complexity and the fact that not many instruments currently measure at this size range. In this study, we used the particle size magnifier (PSM) to measure atmospheric aerosols. Each day was classified into one of the following three event types: a new particle formation (NPF) event, a non-event or a haze event. We then compared four inversion methods (stepwise, kernel, Hagen-Alofs and expectation-maximization) to determine their feasibility to recover the particle size distribution. In addition, we proposed a method to pretreat the measured data, and we introduced a simple test to estimate the efficacy of the inversion itself. Results showed that all four methods inverted NPF events well; however, the stepwise and kernel methods fared poorly when inverting non-events or haze events. This was due to their algorithm and the fact that, when encountering noisy data (e.g. air mass fluctuations or low sub-3 nm particle concentrations) and under the influence of larger particles, these methods overestimated the size distribution and reported artificial particles during inversion. Therefore, using a statistical hypothesis test to discard noisy scans prior to inversion is an important first step toward achieving a good size distribution. After inversion, it is ideal to compare the integrated concentration to the raw estimate (i.e. the concentration difference at the lowest supersaturation and the highest supersaturation) to ascertain whether the inversion itself is sound. Finally, based on the analysis of the inversion methods, we provide procedures and codes related to the PSM data inversion.
  • 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)
  • Fung, Pak Lun; Zaidan, Martha Arbayani; Surakhi, Ola; Tarkoma, Sasu; Petäjä, Tuukka; Hussein, Tareq (2021)
    In air quality research, often only size-integrated particle mass concentrations as indicators of aerosol particles are considered. However, the mass concentrations do not provide sufficient information to convey the full story of fractionated size distribution, in which the particles of different diameters (Dp) are able to deposit differently on respiratory system and cause various harm. Aerosol size distribution measurements rely on a variety of techniques to classify the aerosol size and measure the size distribution. From the raw data the ambient size distribution is determined utilising a suite of inversion algorithms. However, the inversion problem is quite often ill-posed and challenging to solve. Due to the instrumental insufficiency and inversion limitations, imputation methods for fractionated particle size distribution are of great significance to fill the missing gaps or negative values. The study at hand involves a merged particle size distribution, from a scanning mobility particle sizer (NanoSMPS) and an optical particle sizer (OPS) covering the aerosol size distributions from 0.01 to 0.42 µm (electrical mobility equivalent size) and 0.3 to 10 µm (optical equivalent size) and meteorological parameters collected at an urban background region in Amman, Jordan, in the period of 1 August 2016–31 July 2017. We develop and evaluate feed-forward neural network (FFNN) approaches to estimate number concentrations at particular size bin with (1) meteorological parameters, (2) number concentration at other size bins and (3) both of the above as input variables. Two layers with 10–15 neurons are found to be the optimal option. Worse performance is observed at the lower edge (0.01<Dp<0.02 µm), the mid-range region (0.15<Dp<0.5 µm) and the upper edge (6<Dp<10 µm). For the edges at both ends, the number of neighbouring size bins is limited, and the detection efficiency by the corresponding instruments is lower compared to the other size bins. A distinct performance drop over the overlapping mid-range region is due to the deficiency of a merging algorithm. Another plausible reason for the poorer performance for finer particles is that they are more effectively removed from the atmosphere compared to the coarser particles so that the relationships between the input variables and the small particles are more dynamic. An observable overestimation is also found in the early morning for ultrafine particles followed by a distinct underestimation before midday. In the winter, due to a possible sensor drift and interference artefacts, the estimation performance is not as good as the other seasons. The FFNN approach by meteorological parameters using 5 min data (R2= 0.22–0.58) shows poorer results than data with longer time resolution (R2= 0.66–0.77). The FFNN approach using the number concentration at the other size bins can serve as an alternative way to replace negative numbers in the size distribution raw dataset thanks to its high accuracy and reliability (R2= 0.97–1). This negative-number filling approach can maintain a symmetric distribution of errors and complement the existing ill-posed built-in algorithm in particle sizer instruments.
  • Baranizadeh, Elham; Nieminen, Tuomo; Yli-Juuti, Taina; Kulmala, Markku; Petäjä, Tuukka; Leskinen, Ari; Komppula, Mika; Laaksonen, Ari; Lehtinen, Kari E. J. (2017)
    The formation rates of 3 nm particles were estimated at SMEAR IV, Puijo (Finland), where the continuous measurements extend only down to 7 nm in diameter. We extrapolated the formation rates at 7 nm (J(7)) down to 3 nm (J(3)) based on an approximate solution to the aerosol general dynamic equation, assuming a constant condensational growth rate, a power-law size-dependent scavenging rate, and negligible self-coagulation rate for the nucleation mode particles. To evaluate our method, we first applied it to new particle formation (NPF) events in Hyytiala (Finland), which extend down to 3 nm, and, therefore, J(3) and J(7) can be determined directly from the measured size distribution evolution. The Hyytiala results show that the estimated daily mean J(3) values slightly overestimate the observed mean J(3), but a promising 91% of the estimated J(3) values are within a factor of 2 from the measured ones. However, when considering detailed daily time evolution, the agreement is not as good due to fluctuations in data as well as uncertainties in estimated growth rates, which are required in order to calculate the time lag between formation of 3 and 7 nm particles. At Puijo, the mean J(7) for clear NPF days during April 2007-December 2015 was 0.44 cm(-3) s(-1), while the extrapolated mean J(3) was 0.61 cm(-3) s(-1).
  • Kuerten, Andreas; Bianchi, Federico; Almeida, Joao; Kupiainen-Määttä, Oona; Dunne, Eimear M.; Duplissy, Jonathan; Williamson, Christina; Barmet, Peter; Breitenlechner, Martin; Dommen, Josef; Donahue, Neil M.; Flagan, Richard C.; Franchin, Alessandro; Gordon, Hamish; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Ickes, Luisa; Jokinen, Tuija; Kangasluoma, Juha; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Lehtipalo, Katrianne; Leiminger, Markus; Makhmutov, Vladimir; Onnela, Antti; Ortega, Ismael K.; Petäjä, Tuukka; Praplan, Arnaud P.; Riccobono, Francesco; Rissanen, Matti P.; Rondo, Linda; Schnitzhofer, Ralf; Schobesberger, Siegfried; Smith, James N.; Steiner, Gerhard; Stozhkov, Yuri; Tome, Antonio; Trostl, Jasmin; Tsagkogeorgas, Georgios; Wagner, Paul E.; Wimmer, Daniela; Ye, Penglin; Baltensperger, Urs; Carslaw, Ken; Kulmala, Markku; Curtius, Joachim (2016)
    Binary nucleation of sulfuric acid and water as well as ternary nucleation involving ammonia are thought to be the dominant processes responsible for new particle formation (NPF) in the cold temperatures of the middle and upper troposphere. Ions are also thought to be important for particle nucleation in these regions. However, global models presently lack experimentally measured NPF rates under controlled laboratory conditions and so at present must rely on theoretical or empirical parameterizations. Here with data obtained in the European Organization for Nuclear Research CLOUD (Cosmics Leaving OUtdoor Droplets) chamber, we present the first experimental survey of NPF rates spanning free tropospheric conditions. The conditions during nucleation cover a temperature range from 208 to 298K, sulfuric acid concentrations between 5x10(5) and 1x10(9)cm(-3), and ammonia mixing ratios from zero added ammonia, i.e., nominally pure binary, to a maximum of -1400 parts per trillion by volume (pptv). We performed nucleation studies under pure neutral conditions with zero ions being present in the chamber and at ionization rates of up to 75ion pairs cm(-3)s(-1) to study neutral and ion-induced nucleation. We found that the contribution from ion-induced nucleation is small at temperatures between 208 and 248K when ammonia is present at several pptv or higher. However, the presence of charges significantly enhances the nucleation rates, especially at 248K with zero added ammonia, and for higher temperatures independent of NH3 levels. We compare these experimental data with calculated cluster formation rates from the Atmospheric Cluster Dynamics Code with cluster evaporation rates obtained from quantum chemistry.
  • 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.
  • Ahonen, L. R.; Kangasluoma, J.; Lammi, J.; Lehtipalo, K.; Hämeri, K.; Petäjä, T.; Kulmala, M. (2017)
    This study was conducted to observe a potential formation and/or release of aerosol particles related to manufacturing processes inside a cleanroom. We introduce a novel technique to monitor airborne sub 2nm particles in the cleanroom and present results from a measurement campaign during which the total particle number concentration (>1nm and >7 nm) and the size resolved concentration in the 1 to 2nm size range were measured. Measurements were carried out in locations where atomic layer deposition (ALD), sputtering, and lithography processes were conducted, with a wide variety of starting materials. During our campaign in the clean room, we observed several time periods when the particle number concentration was 10(5) cm(-3) in the sub 2nm size range and 10(4) cm(-3) in the size class larger than 7nm in one of the sampling locations. The highest concentrations were related to the maintenance processes of the manufacturing machines, which were conducted regularly in that specific location. Our measurements show that around 500cm(-3) sub 2nm particles or clusters were in practice always present in this specific cleanroom, while the concentration of particles larger than 2nm was less than 2cm(-3). During active processes, the concentrations of sub 2nm particles could rise to over 10(5) cm(-3) due to an active new particle formation. The new particle formation was most likely induced by a combination of the supersaturated vapors, released from the machines, and the very low existing condensation sink, leading to pretty high formation rates J(1.4 nm) = (9 4) cm(-3) s(-1) and growth rates of particles (GR(1.1-1.3 nm) = (6 +/- 3) nm/h and GR(1.3-1.8 nm) = (14 +/- 3) nm/h).Copyright (c) 2017 American Association for Aerosol Research
  • Mentel, T. F.; Springer, M.; Ehn, M.; Kleist, E.; Pullinen, I.; Kurten, T.; Rissanen, Matti; Wahner, A.; Wildt, J. (2015)
    It has been postulated that secondary organic particulate matter plays a pivotal role in the early growth of newly formed particles in forest areas. The recently detected class of extremely low volatile organic compounds (ELVOC) provides the missing organic vapors and possibly contributes a significant fraction to atmospheric SOA (secondary organic aerosol). The sequential rearrangement of peroxy radicals and subsequent O-2 addition results in ELVOC which are highly oxidized multifunctional molecules (HOM). Key for efficiency of such HOM in early particle growth is that their formation is induced by one attack of the oxidant (here O-3), followed by an autoxidation process involving molecular oxygen. Similar mechanisms were recently observed and predicted by quantum mechanical calculations e.g., for isoprene. To assess the atmospheric importance and therewith the potential generality, it is crucial to understand the formation pathway of HOM. To elucidate the formation path of HOM as well as necessary and sufficient structural prerequisites of their formation we studied homologous series of cycloalkenes in comparison to two monoterpenes. We were able to directly observe highly oxidized multifunctional peroxy radicals with 8 or 10 O atoms by an Atmospheric Pressure interface High Resolution Time of Flight Mass Spectrometer (APi-TOF-MS) equipped with a NO3--chemical ionization (CI) source. In the case of O-3 acting as an oxidant, the starting peroxy radical is formed on the so-called vinylhydroperoxide path. HOM peroxy radicals and their termination reactions with other peroxy radicals, including dimerization, allowed for analyzing the observed mass spectra and narrowing down the likely formation path. As consequence, we propose that HOM are multifunctional percarboxylic acids, with carbonyl, hydroperoxy, or hydroxy groups arising from the termination steps. We figured that aldehyde groups facilitate the initial rearrangement steps. In simple molecules like cycloalkenes, autoxidation was limited to both terminal C atoms and two further C atoms in the respective alpha positions. In more complex molecules containing tertiary H atoms or small, constrained rings, even higher oxidation degrees were possible, either by simple H shift of the tertiary H atom or by initialization of complex ring-opening reactions.
  • 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.
  • Kontkanen, Jenni; Järvinen, Emma; Manninen, Hanna E.; Lehtipalo, Katrianne; Kangasluoma, Juha; Decesari, Stefano; Gobbi, Gian Paolo; Laaksonen, Ari; Petäjä, Tuukka; Kulmala, Markku (2016)
    The concentrations of neutral and charged sub3nm clusters and their connection to new particle formation (NPF) were investigated during the PEGASOS campaign (7 June-9 July 2012) at the San Pietro Capofiume measurement station in the Po Valley, Italy. Continuous high concentrations of sub-3nm clusters were detected during the measurement period, although the condensation sink was relatively high (median value 1.1 x 10(-2) s(-1)). The median cluster concentrations were 2140 and 7980 cm 3 in the size bins of 1.5-1.8 and 1.8-3 nm, and the majority of them were electrically neutral. NPF events were observed during the measurement period frequently, on 86% of the days. The median growth rates of clusters during the events were 4.3, 6.0 and 7.2 nm h(-1) in the size ranges of 1.5-3, 3-7 and 720 nm. The median formation rate of 1.6 nm clusters was high, 45 cm 3 s(-1), and it exceeded the median formation rate of 2 nm clusters by 1 order of magnitude. The ion-induced nucleation fraction was low; the median values were 0.7% at 1.6 nm and 3.0% at 2 nm. On NPF event days the neutral cluster concentration had a maximum around 09: 00 (local winter time), which was absent on a non-event day. The increase in the cluster concentrations in the morning coincided with the increase in the boundary layer height. At the same time radiation, temperature and SO2 concentration increased, and RH and condensation sink decreased. The concentrations of neutral and charged clusters were observed to have a positive correlation with sulfuric acid proxy, indicating the significance of sulfuric acid for the cluster formation in San Pietro Capofiume. The condensation sink had a negative correlation with the concentration of charged clusters but no clear relation to the neutral cluster concentration. This finding, together with back-trajectory analysis, suggests that the precursor vapors of the clusters and background aerosol particles, acting as their sink, have possibly originated from the same sources, including e.g., power plants and industrial areas in the Po Valley.
  • 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.
  • Jokinen, T.; Sipilä, M.; Kontkanen, J.; Vakkari, V.; Tisler, P.; Duplissy, E.-M.; Junninen, H.; Kangasluoma, J.; Manninen, H. E.; Petäjä, T.; Kulmala, M.; Worsnop, D. R.; Kirkby, J.; Virkkula, A.; Kerminen, V.-M. (2018)
    Formation of new aerosol particles from trace gases is a major source of cloud condensation nuclei (CCN) in the global atmosphere, with potentially large effects on cloud optical properties and Earth's radiative balance. Controlled laboratory experiments have resolved, in detail, the different nucleation pathways likely responsible for atmospheric new particle formation, yet very little is known from field studies about the molecular steps and compounds involved in different regions of the atmosphere. The scarcity of primary particle sources makes secondary aerosol formation particularly important in the Antarctic atmosphere. Here, we report on the observation of ion-induced nucleation of sulfuric acid and ammonia-a process experimentally investigated by the CERN CLOUD experiment-as a major source of secondary aerosol particles over coastal Antarctica. We further show that measured high sulfuric acid concentrations, exceeding 10(7) molecules cm(-3), are sufficient to explain the observed new particle growth rates. Our findings show that ion-induced nucleation is the dominant particle formation mechanism, implying that galactic cosmic radiation plays a key role in new particle formation in the pristine Antarctic atmosphere.
  • Rose, C.; Sellegri, K.; Asmi, E.; Hervo, M.; Freney, E.; Colomb, A.; Junninen, H.; Duplissy, J.; Sipilä, Mikko; Kontkanen, J.; Lehtipalo, K.; Kulmala, Markku (2015)
    The formation of new aerosol particles in the atmosphere is a key process influencing the aerosol number concentration as well as the climate, in particular at high altitude, where the newly formed particles directly influence cloud formation. However, free tropospheric new particle formation (NPF) is poorly documented due to logistic limitations and complex atmospheric dynamics around high-altitude stations that make the observation of this day-time process challenging. Recent improvements in measurement techniques make now possible the detection of neutral clusters down to similar to 1 nm sizes, which opens new horizons in our understanding of the nucleation process. Indeed, only the charged fraction of clusters has been reported in the upper troposphere up to now. Here we report day-time concentrations of charged and neutral clusters (1 to 2.5 nm mobility diameter) recorded at the interface between the boundary layer (BL) and the FT as well as in the FT at the altitude site of Puy de Dome (1465 m a.s.l.), central France, between 10 and 29 February 2012. Our findings demonstrate that in the FT, and especially at the interface between the BL and the FT, the formation of 1.5 nm neutral clusters significantly exceeds the one of ionic clusters during NPF events, clearly indicating that they dominate in the nucleation process. We also observe that the total cluster concentration significantly increases during NPF events compared to the other days, which was not clearly observed for the charged cluster population in the past. During the studied period, the nucleation process does not seem to be sulfuric acid-limited and could be promoted by the transport of pollutants to the upper troposphere, coupled with low temperatures.
  • 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.
  • Sarnela, Nina; Jokinen, Tuija; Duplissy, Jonathan; Yan, Chao; Nieminen, Tuomo; Ehn, Mikael; Schobesberger, Siegfried; Heinritzi, Martin; Ehrhart, Sebastian; Lehtipalo, Katrianne; Tröstl, Jasmin; Simon, Mario; Kürten, Andreas; Leiminger, Markus; Lawler, Michael J.; Rissanen, Matti P.; Bianchi, Federico; Praplan, Arnaud P.; Hakala, Jani; Amorim, Antonio; Gonin, Marc; Hansel, Armin; Kirkby, Jasper; Dommen, Josef; Curtius, Joachim; Smith, James N.; Petäjä, Tuukka; Worsnop, Douglas R.; Kulmala, Markku; Donahue, Neil M.; Sipilä, Mikko (2018)
    Atmospheric oxidation is an important phenomenon which produces large quantities of low-volatility compounds such as sulfuric acid and oxidized organic compounds. Such species may be involved in the nucleation of particles and enhance their subsequent growth to reach the size of cloud condensation nuclei (CCN). In this study, we investigate alpha-pinene, the most abundant monoterpene globally, and its oxidation products formed through ozonolysis in the Cosmic Leaving OUtdoor Droplets (CLOUD) chamber at CERN (the European Organization for Nuclear Research). By scavenging hydroxyl radicals (OH) with hydrogen (H-2), we were able to investigate the formation of highly oxygenated molecules (HOMs) purely driven by ozonolysis and study the oxidation of sulfur dioxide (SO2) driven by stabilized Criegee intermediates (sCIs). We measured the concentrations of HOM and sulfuric acid with a chemical ionization atmospheric-pressure interface time-of-flight (CI-APi-TOF) mass spectrometer and compared the measured concentrations with simulated concentrations calculated with a kinetic model. We found molar yields in the range of 3.5-6.5% for HOM formation and 22-32% for the formation of stabilized Criegee intermediates by fitting our model to the measured sulfuric acid concentrations. The simulated time evolution of the ozonolysis products was in good agreement with measured concentrations except that in some of the experiments sulfuric acid formation was faster than simulated. In those experiments the simulated and measured concentrations met when the concentration reached a plateau but the plateau was reached 20-50 min later in the simulations. The results shown here are consistent with the recently published yields for HOM formation from different laboratory experiments. Together with the sCI yields, these results help us to understand atmospheric oxidation processes better and make the reaction parameters more comprehensive for broader use.
  • 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.
  • Kristensson, Adam; Johansson, Martin; Swietlicki, Erik; Kivekas, Niku; Hussein, Tareq; Nieminen, Tuomo; Kulmala, Markku; Dal Maso, Miikka (2014)
    Particle number size distributions at various field sites are used to identify atmospheric new-particle formation (NPF) event days. However, the spatial distribution of regionally extensive events is unknown. To remedy this situation, the NanoMap method has been developed to enable the estimation of where NPF occurs within 500 km from any field station using as input size distribution and meteorological trajectories only. Also, the horizontal extension of NPF can be determined. An open-source program to run NanoMap is available on the internet. NanoMap has been developed using as an example the Finnish field site at Hyytiala. It shows that there are frequent NPF events over the Baltic Sea, but not as frequent as over Finland for certain wind directions; hence NanoMap is able to pinpoint areas with a low or high occurrence of NPF events. The method should be applicable to almost any field site.
  • Rose, Clémence; Zha, Qiaozhi; Dada, Lubna; Yan, Chao; Lehtipalo, Katrianne; Junninen, Heikki; Mazon, Stephany Buenrostro; Jokinen, Tuija; Sarnela, Nina; Sipilä, Mikko; Petäjä, Tuukka; Kerminen, Veli-Matti; Bianchi, Federico; Kulmala, Markku (2018)
    A substantial fraction of aerosols, which affect air quality and climate, is formed from gaseous precursors. Highly oxygenated organic molecules (HOMs) are essential to grow the newly formed particles and have been evidenced to initiate ion-induced nucleation in chamber experiments in the absence of sulfuric acid. We investigate this phenomenon in the real atmosphere using an extensive set of state-of-the-art ion and mass spectrometers deployed in a boreal forest environment. We show that within a few hours around sunset, HOMs resulting from the oxidation of monoterpenes are capable of forming and growing ion clusters even under low sulfuric acid levels. In these conditions, we hypothesize that the lack of photochemistry and essential vapors prevents the organic clusters from growing past 6 nm. However, this phenomenon might have been a major source of particles in the preindustrial atmosphere and might also contribute to particle formation in the future and consequently affect the climate.