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Simon Schallhart

Bio: Simon Schallhart is an academic researcher from University of Helsinki. The author has contributed to research in topics: Cloud condensation nuclei & Particle. The author has an hindex of 19, co-authored 28 publications receiving 2158 citations. Previous affiliations of Simon Schallhart include University of Innsbruck & Finnish Meteorological Institute.

Papers
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Journal ArticleDOI
Joao Almeida1, Joao Almeida2, Siegfried Schobesberger3, Andreas Kürten1, Ismael K. Ortega3, Oona Kupiainen-Määttä3, Arnaud P. Praplan4, Alexey Adamov3, António Amorim5, F. Bianchi4, Martin Breitenlechner6, A. David2, Josef Dommen4, Neil M. Donahue7, Andrew J. Downard8, Eimear M. Dunne9, Jonathan Duplissy3, Sebastian Ehrhart1, Richard C. Flagan8, Alessandro Franchin3, Roberto Guida2, Jani Hakala3, Armin Hansel6, Martin Heinritzi6, Henning Henschel3, Tuija Jokinen3, Heikki Junninen3, Maija Kajos3, Juha Kangasluoma3, Helmi Keskinen10, Agnieszka Kupc11, Theo Kurtén3, Alexander N. Kvashin12, Ari Laaksonen13, Ari Laaksonen10, Katrianne Lehtipalo3, Markus Leiminger1, Johannes Leppä13, Ville Loukonen3, Vladimir Makhmutov12, Serge Mathot2, Matthew J. McGrath14, Tuomo Nieminen15, Tuomo Nieminen3, Tinja Olenius3, Antti Onnela2, Tuukka Petäjä3, Francesco Riccobono4, Ilona Riipinen16, Matti P. Rissanen3, Linda Rondo1, Taina Ruuskanen3, Filipe Duarte Santos5, Nina Sarnela3, Simon Schallhart3, R. Schnitzhofer6, John H. Seinfeld8, Mario Simon1, Mikko Sipilä3, Mikko Sipilä15, Yuri Stozhkov12, Frank Stratmann17, António Tomé5, Jasmin Tröstl4, Georgios Tsagkogeorgas17, Petri Vaattovaara10, Yrjö Viisanen13, Annele Virtanen10, Aron Vrtala11, Paul E. Wagner11, Ernest Weingartner4, Heike Wex17, Christina Williamson1, Daniela Wimmer1, Daniela Wimmer3, Penglin Ye7, Taina Yli-Juuti3, Kenneth S. Carslaw9, Markku Kulmala15, Markku Kulmala3, Joachim Curtius1, Urs Baltensperger4, Douglas R. Worsnop, Hanna Vehkamäki3, Jasper Kirkby2, Jasper Kirkby1 
17 Oct 2013-Nature
TL;DR: The results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.
Abstract: Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei(1). Aerosols can cause a net cooling of climate by scattering sun ...

738 citations

Journal ArticleDOI
16 May 2014-Science
TL;DR: It is shown, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere.
Abstract: Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations.

446 citations

Journal ArticleDOI
TL;DR: High-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research confirm that oxidized organics are involved in both the formation and growth of particles under ambient conditions.
Abstract: Atmospheric aerosols formed by nucleation of vapors affect radiative forcing and therefore climate. However, the underlying mechanisms of nucleation remain unclear, particularly the involvement of organic compounds. Here, we present high-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research. The experiments involved sulfuric acid vapor and different stabilizing species, including ammonia and dimethylamine, as well as oxidation products of pinanediol, a surrogate for organic vapors formed from monoterpenes. A striking resemblance is revealed between the mass spectra from the chamber experiments with oxidized organics and ambient data obtained during new particle formation events at the Hyytiala boreal forest research station. We observe that large oxidized organic compounds, arising from the oxidation of monoterpenes, cluster directly with single sulfuric acid molecules and then form growing clusters of one to three sulfuric acid molecules plus one to four oxidized organics. Most of these organic compounds retain 10 carbon atoms, and some of them are remarkably highly oxidized (oxygen-to-carbon ratios up to 1.2). The average degree of oxygenation of the organic compounds decreases while the clusters are growing. Our measurements therefore connect oxidized organics directly, and in detail, with the very first steps of new particle formation and their growth between 1 and 2 nm in a controlled environment. Thus, they confirm that oxidized organics are involved in both the formation and growth of particles under ambient conditions.

301 citations

Journal ArticleDOI
TL;DR: The prompt formation of highly oxidized organic compounds in the ozonolysis of cyclohexene (C6H10) was investigated by means of laboratory experiments together with quantum chemical calculations, giving a consistent picture of a formation mechanism advancing by peroxy radical (RO2) isomerization through intramolecular hydrogen shift reactions, followed by sequential O2 addition steps.
Abstract: The prompt formation of highly oxidized organic compounds in the ozonolysis of cyclohexene (C6H10) was investigated by means of laboratory experiments together with quantum chemical calculations. The experiments were performed in borosilicate glass flow tube reactors coupled to a chemical ionization atmospheric pressure interface time-of-flight mass spectrometer with a nitrate ion (NO3–)-based ionization scheme. Quantum chemical calculations were performed at the CCSD(T)-F12a/VDZ-F12//ωB97XD/aug-cc-pVTZ level, with kinetic modeling using multiconformer transition state theory, including Eckart tunneling corrections. The complementary investigation methods gave a consistent picture of a formation mechanism advancing by peroxy radical (RO2) isomerization through intramolecular hydrogen shift reactions, followed by sequential O2 addition steps, that is, RO2 autoxidation, on a time scale of seconds. Dimerization of the peroxy radicals by recombination and cross-combination reactions is in competition with the...

235 citations

Journal ArticleDOI
Katrianne Lehtipalo1, Katrianne Lehtipalo2, Katrianne Lehtipalo3, Chao Yan1, Lubna Dada1, F. Bianchi1, Mao Xiao3, Robert Wagner1, Dominik Stolzenburg4, Lauri Ahonen1, António Amorim5, Andrea Baccarini3, Paulus Salomon Bauer4, Bernhard Baumgartner4, Anton Bergen6, Anne-Kathrin Bernhammer7, Martin Breitenlechner7, Sophia Brilke4, Angela Buchholz8, Stephany Buenrostro Mazon1, Dexian Chen9, Xuemeng Chen1, A.A. Dias5, Josef Dommen3, Danielle C. Draper10, Jonathan Duplissy1, Mikael Ehn1, Henning Finkenzeller11, Lukas Fischer7, Carla Frege3, Claudia Fuchs3, Olga Garmash1, Hamish Gordon12, Jani Hakala1, Xucheng He1, Liine Heikkinen1, Martin Heinritzi6, Johanna Helm6, Victoria Hofbauer9, Christopher R. Hoyle3, Tuija Jokinen1, Juha Kangasluoma13, Juha Kangasluoma1, Veli-Matti Kerminen1, Changhyuk Kim14, Jasper Kirkby6, Jasper Kirkby15, Jenni Kontkanen16, Jenni Kontkanen1, Andreas Kürten6, Michael J. Lawler10, Huajun Mai14, Serge Mathot15, Roy L. Mauldin11, Roy L. Mauldin9, Ugo Molteni3, Leonid Nichman17, Wei Nie1, Wei Nie18, Tuomo Nieminen8, Andrea Ojdanic4, Antti Onnela15, Monica Passananti1, Tuukka Petäjä18, Tuukka Petäjä1, Felix Piel7, Felix Piel6, Veronika Pospisilova3, Lauriane L. J. Quéléver1, Matti P. Rissanen1, Clémence Rose1, Nina Sarnela1, Simon Schallhart1, Simone Schuchmann15, Kamalika Sengupta12, Mario Simon6, Mikko Sipilä1, Christian Tauber4, António Tomé19, Jasmin Tröstl3, Olli Väisänen8, Alexander L. Vogel6, Alexander L. Vogel3, Rainer Volkamer11, Andrea Christine Wagner6, Mingyi Wang9, Lena Weitz6, Daniela Wimmer1, Penglin Ye9, Arttu Ylisirniö8, Qiaozhi Zha1, Kenneth S. Carslaw12, Joachim Curtius6, Neil M. Donahue1, Neil M. Donahue9, Richard C. Flagan14, Armin Hansel1, Armin Hansel7, Ilona Riipinen16, Ilona Riipinen20, Annele Virtanen8, Paul M. Winkler4, Urs Baltensperger3, Markku Kulmala1, Markku Kulmala21, Markku Kulmala13, Douglas R. Worsnop1 
TL;DR: How NOx suppresses particle formation is shown, while HOMs, sulfuric acid, and NH3 have a synergistic enhancing effect on particle formation, elucidate the complex interactions between biogenic and anthropogenic vapors in the atmospheric aerosol system.
Abstract: 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.

165 citations


Cited by
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TL;DR: A periodic cycle of PM episodes in Beijing is demonstrated that is governed by meteorological conditions and characterized by two distinct aerosol formation processes of nucleation and growth, but with a small contribution from primary emissions and regional transport of particles.
Abstract: As the world’s second largest economy, China has experienced severe haze pollution, with fine particulate matter (PM) recently reaching unprecedentedly high levels across many cities, and an understanding of the PM formation mechanism is critical in the development of efficient mediation policies to minimize its regional to global impacts. We demonstrate a periodic cycle of PM episodes in Beijing that is governed by meteorological conditions and characterized by two distinct aerosol formation processes of nucleation and growth, but with a small contribution from primary emissions and regional transport of particles. Nucleation consistently precedes a polluted period, producing a high number concentration of nano-sized particles under clean conditions. Accumulation of the particle mass concentration exceeding several hundred micrograms per cubic meter is accompanied by a continuous size growth from the nucleation-mode particles over multiple days to yield numerous larger particles, distinctive from the aerosol formation typically observed in other regions worldwide. The particle compositions in Beijing, on the other hand, exhibit a similarity to those commonly measured in many global areas, consistent with the chemical constituents dominated by secondary aerosol formation. Our results highlight that regulatory controls of gaseous emissions for volatile organic compounds and nitrogen oxides from local transportation and sulfur dioxide from regional industrial sources represent the key steps to reduce the urban PM level in China.

1,291 citations

Journal ArticleDOI
TL;DR: Air pollutants consist of a complex combination of gases and particulate matter, which is emitted directly into the atmosphere or formed in the atmosphere through gas-to-particle conversion (secondary) (Figure 1).
Abstract: Urban air pollution represents one of the greatest environmental challenges facing mankind in the 21st century. Noticeably, many developing countries, such as China and India, have experienced severe air pollution because of their fast-developing economy and urbanization. Globally, the urbanization trend is projected to continue: 70% of the world population will reside in urban centers by 2050, and there will exist 41 megacities (with more than 10 million inhabitants) by 2030. Air pollutants consist of a complex combination of gases and particulate matter (PM). In particular, fine PM (particles with the aerodynamic diameter smaller than 2.5 μm or PM_(2.5)) profoundly impacts human health, visibility, the ecosystem, the weather, and the climate, and these PM effects are largely dependent on the aerosol properties, including the number concentration, size, and chemical composition. PM is emitted directly into the atmosphere (primary) or formed in the atmosphere through gas-to-particle conversion (secondary) (Figure 1). Also, primary and secondary PM undergoes chemical and physical transformations and is subjected to transport, cloud processing, and removal from the atmosphere.

931 citations

Journal ArticleDOI
TL;DR: In this article, a call to action targets a reversal of paradigms, from a carbon-centric model to one that treats the hydrologic and climate cooling effects of trees and forests as the first order of priority.
Abstract: Forest-driven water and energy cycles are poorly integrated into regional, national, continental and global decision-making on climate change adaptation, mitigation, land use and water management. This constrains humanity's ability to protect our planet's climate and life-sustaining functions. The substantial body of research we review reveals that forest, water and energy interactions provide the foundations for carbon storage, for cooling terrestrial surfaces and for distributing water resources. Forests and trees must be recognized as prime regulators within the water, energy and carbon cycles. If these functions are ignored, planners will be unable to assess, adapt to or mitigate the impacts of changing land cover and climate. Our call to action targets a reversal of paradigms, from a carbon-centric model to one that treats the hydrologic and climate-cooling effects of trees and forests as the first order of priority. For reasons of sustainability, carbon storage must remain a secondary, though valuable, by-product. The effects of tree cover on climate at local, regional and continental scales offer benefits that demand wider recognition. The forest- and tree-centered research insights we review and analyze provide a knowledge-base for improving plans, policies and actions. Our understanding of how trees and forests influence water, energy and carbon cycles has important implications, both for the structure of planning, management and governance institutions, as well as for how trees and forests might be used to improve sustainability, adaptation and mitigation efforts.

668 citations

Journal ArticleDOI
TL;DR: The literature on atmospheric particulate maffer (PM), or atmospheric aerosol, has increased enormously over the last 2 decades and amounts now to some 1500-2000 papers per year in the refereed literature.
Abstract: The literature on atmospheric particulate maffer (PM), or atmospheric aerosol, has increased enormously over the last 2 decades and amounts now to some 1500—2000 papers per year in the refereed literature. This is in part due to the enormous advances in measurement technologies, which have allowed for an increasingly accurate understanding of the chemical composition and of the physical properties of atmospheric particles and of their processes in the atmosphere. The growing scientific interest in atmospheric aerosol particles is due to their high importance for environmental policy. In fact, particulate maffer constitutes one of the most challenging problems both for air quality and for climate change policies. In this context, this paper reviews the most recent results within the atmospheric aerosol sciences and thepoticy needs, which have driven much ofthe increase in monitoring and mechanistic research over the last 2 decades. The synthesis reveals many new processes and developments in the science underpinning climate—aerosol interactions and effects of PM on human health and the environment. However, while airborne particulate matter is responsible for globally important influences on premature human mortality, we stijl do not know the relative importance of the different chemical components of PM for these effects. Likewise, the magnitude of the overall effects of PM on climate remains highly uncertain. Despite the uncertainty there are many things that could be done to mitigate local and global problems of atmospheric PM. Recent analyses have shown that reducing black carbon (BC) emissions, using known control measures, would reduce global wanning and delay the time when anthropogenic effects on global temperature would exceed 2°C. Likewise, cost-effective control measures on ammonia, an important agricultural precursor gas for secondary inorganic aerosols (SlA), would reduce regional eutrophication and PM concentrations in large areas of Europe, China and the USA. Thus, there is much that could be done to reduce the effects of atmospheric PM on the climate and the health of the environment and the human population. A prioritized list of actions to mitigate the full range of effects ofPM is currently undeliverable due to shortcomings in the knowledge of aerosol science; among the shortcomings, the roles of PM in global climate and the relative roles of different PM precursor sources and their response to climate and land use change over the remaining decades of this century are prominent. In any case, the evidence from this paper strongly advocates for an integrated approach to air quality and climate policies.

648 citations