Hydrocarbons are emitted into the Earth's atmosphere in very large quantities by human and biogenic activities. Their atmospheric oxidation processes almost exclusively yield ROradicals as reactive intermediates whose atmospheric fate is not yet fully unraveled. Herein, we show that gas-phase reactions of two ROradicals produce accretion products composed of the carbon backbone of both reactants. The rates for accretion product formation are very high for ROradicals bearing functional groups, competing with those of the corresponding reactions with NO and HO. This pathway, which has not yet been considered in the modelling of atmospheric processes, can be important, or even dominant, for the fate of ROradicals in all areas of the atmosphere. Moreover, the vapor pressure of the formed accretion products can be remarkably low, characterizing them as an effective source for the secondary organic aerosol.

Berndt Torsten    Scholz Wiebke    Mentler Bernhard    Fischer    Hartmut Herrmann    Markku Kulmala     Armin Hänsel   

Angewandte Chemie - International Edition

2018

The Pan-Eurasian Experiment (PEEX) program was initiated as a bottom-up approach by the researchers coming from Finland and Russia in October 2012. The PEEX China kick off meeting was held in November 2013. During its five years in operation, the program has established a governance structure and delivered a science plan for the Northern Eurasian region. PEEX has also introduced a concept design for a modelling platform and ground-based in situ observation systems for detecting land-atmosphere and ocean-atmosphere interactions. Today, PEEX has an extensive researcher’s network representing research communities coming from the Nordic countries, Russia and China. PEEX is currently carrying out its research activities on a project basis, but is looking for more coordinated funding bases, especially in Russia and in China. The near-future challenge in implementing the PEEX research agenda is to achieve a successful integration and identification of the methodological approaches of the socio-economic research to environmental sciences. Here we give insight into these issues and provide an overview on the main tasks for the upcoming years.

Lappalainen    Altimir Nuria    Veli matti Kerminen    Tuukka Petäj̈ä T.    Makkonen    Alekseychik Pavel    Zaitseva Nina    Bashmakova Irina    Kujansuu    Lauri Antti    Haapanala    Mazon Stephany    Borisova Alla    Konstantinov Pavel    Chalov Sergey    Laurila    Asmi    Lihavainen Heikki    Bäck    Arshinov    Mahura Alexander    Arnold    Vihma Timo    Uotila Petteri    De Leeuw    Kukkonen Ilmo    Malkhazova Svetlana M.    Tynkkynen    Fedorova Irina    Hansson Hans-Christian    Dobrolyubov Sergey    Melnikov Vladimir    Matvienko Gennady G.    Baklanov    Viisanen Yrjö    Kasimov    Guo Huadong    Bondur    Sergej Zilitinkevich    Markku Kulmala    

Geography, Environment, Sustainability

2018

The measurement of sub-3nm aerosol particles is technically challenging. Therefore, there is a lack of knowledge about the concentrations of atmospheric sub-3nm particles and their variation in different environments. In this study, the concentrations of ∼1-3nm particles measured with a particle size magnifier (PSM) were investigated at nine sites around the world. Sub-3nm 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-3nm 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-3nm 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-3nm 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-3nm particles separately in different size ranges is essential.

Kontkanen Jenni    Lehtipalo    Ahonen    Juha Kangasluoma    Manninen Hanna E.    Hakala    Rose    Sellegri    Shan Xiao    Wang Lin    Qi    Wei Nie    丁爱军    Yu Huan    Lee Shanhu    Veli matti Kerminen    Tuukka Petäj̈ä T.    Markku Kulmala    

Atmospheric Chemistry and Physics

2017

We present ambient observations of dimeric monoterpene oxidation products (CHO) in gas and particle phases in the boreal forest in Finland in spring 2013 and 2014, detected with a chemical ionization mass spectrometer with a filter inlet for gases and aerosols employing acetate and iodide as reagent ions. These are among the first online dual-phase observations of such dimers in the atmosphere. Estimated saturation concentrations of 10 to 10 µg m (based on observed thermal desorptions and group-contribution methods) and measured gas-phase concentrations of 10 to 10 µg m (~10–10 molecules cm) corroborate a gas-phase formation mechanism. Regular new particle formation (NPF) events allowed insights into the potential role dimers may play for atmospheric NPF and growth. The observationally constrained Model for Acid-Base chemistry in NAnoparticle Growth indicates a contribution of ~5% to early stage particle growth from the ~60 gaseous dimer compounds.

Mohr Claudia    Lopez-Hilfiker Felipe    Yli-Juuti    Heitto Arto    Lutz Anna    Hallquist    D'Ambro Emma L.    Rissanen Matti    Hao Liqing    Siegfried Schobesberger    Markku Kulmala     Mauldin Roy L.    Makkonen    Sipilä Mikko    Tuukka Petäj̈ä T.    Thornton   

Geophysical Research Letters

2017

Few studies reported the formation of Ti-containing clusters in the initial stages of TiO flame synthesis. The conversion from synthesis precursor to TiO monomers was commonly assumed to take place through global reaction such as thermal decomposition and/or hydrolysis at high temperatures. More recent studies have been able to identify stable intermediates of Ti-containing monomers, most commonly Ti(OH), as the final step before the formation of TiO. However, no larger Ti-containing cluster formation mechanisms or interactions between these monomers have been tracked. To investigate cluster formation pathways of TiO during flame synthesis, Charged clusters were measured in an atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometer. TiO nanoparticles were synthesized by adding titanium tetraisopropoxide (TTIP) precursor to a premixed CH/O/N flat flame aerosol reactor. Pure TiO clusters were not detected by the APi-TOF. Results from measured mass spectra and mass defect plots show that for positively charged clusters, the abstraction of CH groups occurs simultaneously with the clustering of larger intermediate organometallic species. For negatively charged clusters, NO formation pathways in the flame may play a role during the initial stages of TiO formation, since a lot of Ti-containing clusters were attached with nitrate-related species. These research findings provide insights on quantum dot synthesis and molecular doping where rapid dilution of the flame synthesized nanoparticles is needed to better control the particle size and chemical composition. The possible influences of and potential artifacts brought by the dilution system on observing the incipient particle formation in flames were also discussed.

Fang Jiaxi    Wang Yang    Juha Kangasluoma    Attoui    Heikki Junninen    Markku Kulmala     Tuukka Petäj̈ä T.    Pratim Biswas   

Aerosol Science and Technology

2017

In this study we characterized the performance of three new particle counters able to detect particles smaller than 3 nm during the Helsinki condensation particle counter (CPC) workshop in summer 2016: the Aerosol Dynamics Inc. (ADI; Berkeley, USA) versatile water condensation particle counter (vWCPC), TSI 3777 nano enhancer (TSI Inc., Shoreview, USA) and modified and boosted TSI 3010-type CPC from Université Blaise Pascal called a B3010. The performance of all CPCs was first measured with charged tungsten oxide test particles at temperature settings which resulted in supersaturation low enough to not detect any ions produced by a radioactive source. Due to similar measured detection efficiencies, additional comparison between the 3777 and vWCPC were conducted using electrically neutral tungsten oxide test particles and with positively charged tetradodecylammonium bromide. Furthermore, the detection efficiencies of the 3777 and vWCPC were measured with boosted temperature settings yielding supersaturation which was at the onset of homogeneous nucleation for the 3777 or confined within the range of liquid water for the ADI vWCPC. Finally, CPC-specific tests were conducted to probe the response of the 3777 to various inlet flow relative humidities, of the B3010 to various inlet flow rates and of the vWCPC to various particle concentrations. For the 3777 and vWCPC the measured 50 % detection diameters (d50s) were in the range of 1.3-2.4 nm for the tungsten oxide particles, depending on the particle charging state and CPC temperature settings, between 2.5 and 3.3 nm for the organic test aerosol, and in the range of 3.2-3.4 nm for tungsten oxide for the B3010.

Juha Kangasluoma    Hering Susanne V.    Picard    Lewis    Enroth Joonas    Korhonen Frans    Markku Kulmala     Sellegri    Attoui    Tuukka Petäj̈ä T.   

Atmospheric Measurement Techniques

2017

We report comprehensive, demonstrably contaminant-free measurements of binary particle formation rates by sulfuric acid and water for neutral and ion-induced pathways conducted in the European Organization for Nuclear Research Cosmics Leaving Outdoor Droplets chamber. The recently developed Atmospheric Pressure interface-time of flight-mass spectrometer was used to detect contaminants in charged clusters and to identify runs free of any contaminants. Four parameters were varied to cover ambient conditions: sulfuric acid concentration (10 to 10 mol cm), relative humidity (11% to 58%), temperature (207 K to 299 K), and total ion concentration (0 to 6800 ions cm). Formation rates were directly measured with novel instruments at sizes close to the critical cluster size (mobility size of 1.3 nm to 3.2 nm). We compare our results with predictions from Classical Nucleation Theory normalized by Quantum Chemical calculation (QC-normalized CNT), which is described in a companion paper. The formation rates predicted by the QC-normalized CNT were extended from critical cluster sizes to measured sizes using the UHMA2 sectional particle microphysics model. Our results show, for the first time, good agreement between predicted and measured particle formation rates for the binary (neutral and ion-induced) sulfuric acid-water system. Formation rates increase with RH, sulfuric acid, and ion concentrations and decrease with temperature at fixed RH and sulfuric acid concentration. Under atmospheric conditions, neutral particle formation dominates at low temperatures, while ion-induced particle formation dominates at higher temperatures. The good agreement between the theory and our comprehensive data set gives confidence in using the QC-normalized CNT as a powerful tool to study neutral and ion-induced binary particle formation in atmospheric modeling.

Jonathan Duplissy    Merikanto    Alessandro Franchin    Georgios Tsagkogeorgas    Juha Kangasluoma    Daniela Wimmer    Vuollekoski Henri    Siegfried Schobesberger    Lehtipalo    Richard Flagan    Brus    Neil mc pherson Donahue    Hanna Vehkamäki    João Almeida    Amorim A.    Barmet    Federico Bianchi    Martin Breitenlechner    Eimear Dunne    Roberto Guida    Henschel Henning    Heikki Junninen    Jasper Kirkby    Kürten    Agnieszka Kupć    Määttänen    Makhmutov    Mathot    Nieminen Tuomo    Antti Onnela    Praplan    Riccobono Francesco    Linda Rondo    Steiner Gerhard    António Tomé    Walther    Urs Baltensperger    Kenneth Carslaw    Josef Dommen    Armin Hänsel    Tuukka Petäj̈ä T.    Sipilä Mikko    Stratmann Frank    Vrtala Aron    Wagner Paul E.    Douglas Worsnop    Curtius    Markku Kulmala    

Journal of Geophysical Research: Atmospheres

2016

Heterogeneous nucleation of vapor on a seed particle surface is dependent on the seed properties such as size, chemical composition, and electric charging state, of which the significance of the charging state has not been uncovered unambiguously. The underlying problem is that, on the molecular level, the charging state and the chemical composition of the seed are connected and cannot be well separated without a direct mass spectrometric measurement of the ion. By generating sub-3 nm size selected seeds of different size, chemical composition, electric charging state, and letting three different vapors nucleate onto the seeds, we show that heterogeneous nucleation does not clearly prefer either positive or negative seeds. Rather, the most important parameter determining the nucleation probability in the sub-3 nm size range was the seed chemical composition. Our findings help to understand the dynamics in various nanoparticle systems, such as nucleation chambers, industrial processes, or atmospheric aerosols.

Juha Kangasluoma    Samodurov    Attoui    Alessandro Franchin    Heikki Junninen    Korhonen Frans    Kurtén    Hanna Vehkamäki    Sipilä Mikko    Lehtipalo    Douglas Worsnop    Tuukka Petäj̈ä T.    Markku Kulmala    

Journal of Physical Chemistry C

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 (Hyytiälä, 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.

Markku Kulmala     Luoma Krista    Virkkula A.    Tuukka Petäj̈ä T.    Paasonen    Veli matti Kerminen    Wei Nie    Qi    Shen    Xuguang Chi    丁爱军   

Boreal Environment Research

2016

New particle formation (NPF) is the source of over half of the atmosphere's cloud condensation nuclei, thus influencing cloud properties and Earth's energy balance. Unlike in the planetary boundary layer, few observations of NPF in the free troposphere exist. We provide observational evidence that at high altitudes, NPF occurs mainly through condensation of highly oxygenated molecules (HOMs), in addition to taking place through sulfuric acid-ammonia nucleation. Neutral nucleation is more than 10 times faster than ion-induced nucleation, and growth rates are size-dependent. NPF is restricted to a time window of 1 to 2 days after contact of the air masses with the planetary boundary layer; this is related to the time needed for oxidation of organic compounds to form HOMs. These findings require improved NPF parameterization in atmospheric models.

Federico Bianchi    Tröstl Jasmin    Heikki Junninen    Carla Frege    Henne    Hoyle    Ugo Molteni    Erik Herrmann    Alexey yu Adamov    Bukowiecki Nicolas    Xuemeng Chen    Jonathan Duplissy    Gysel    Hutterli Manuel A.    Juha Kangasluoma    Kontkanen Jenni    Kürten    Manninen Hanna E.    Münch    Otso Peräkylä O    Tuukka Petäj̈ä T.    Linda Rondo    Christina Williamson    Ernest Weingartner    Curtius    Douglas Worsnop    Markku Kulmala     Josef Dommen    Urs Baltensperger   

Science

2016