Scientific paper

CO2-induced terrestrial climate feedback mechanism: From carbon sink to aerosol source and back

Kulmala, M.; Nieminen, T.; Nikandrova, A.; Lehtipalo, K.; Manninen, H.E.; Kajos, M.A.; Kolari, P.; Lauri, A.; Petäjä, T.; Krejci, R.; Hansson, H.-C.; Swietlicki, E.; Lindroth, A.; Christensen, T.R.; Arneth, A.; Hari, P.; Bäck, J.; Vesala, T.; Kerminen V.-M.
2014 | Boreal Environ. Res. | 19 (122-131)

Feedbacks mechanisms are essential components of our climate system, as they either increase or decrease changes in climate-related quantities in the presence of external forcings. In this work, we provide the first quantitative estimate regarding the terrestrial climate feedback loop connecting the increasing atmospheric carbon dioxide concentration, changes in gross primary production (GPP) associated with the carbon uptake, organic aerosol formation in the atmosphere, and transfer of both diffuse and global radiation. Our approach was to combine process-level understanding with comprehensive, long-term field measurement data set collected from a boreal forest site in southern Finland. Our best estimate of the gain in GPP resulting from the feedback is 1.3 (range 1.02-1.5), which is larger than the gains of the few atmospheric chemistry-climate feedbacks estimated using large-scale models. Our analysis demonstrates the power of using comprehensive field measurements in investigating the complicated couplings between the biosphere and atmosphere on one hand, and the need for complementary approaches relying on the combination of field data, satellite observations model simulations on the other hand.

Technical report

Black carbon – Possibilities to reduce emissions and potential effects.

Hansson, HC.; Johansson, C.; Nyquist, G.; Kindbom, K.; Åström, S.; Moldanovna, J.
2011 | Report, ITM, SU | Report No: ITM report 202
Scientific paper

Primary versus secondary contributions to particle number concentrations in the European boundary layer

Reddington, CL; Carslaw, KS; Spracklen, DV; Frontoso, MG; Collins, L; Merikanto, J; Minikin, A; Hamburger, T; Coe, H; Kulmala, M; Aalto, P; Flentje, H; Plass-Duelmer, C; Birmili, W; Wiedensohler, A; Wehner, B; Tuch, T; Sonntag, A; O'Dowd, CD; Jennings, SG; Dupuy, R; Baltensperger, U; Weingartner, E; Hansson, HC; Tunved, P; Laj, P; Sellegri, K; Boulon, J; Putaud, JP; Gruening, C; Swietlicki, E; Roldin, P; Henzing, JS; Moerman, M; Mihalopoulos, N; Kouvarakis, G; Zdimal, V; Zikova, N; Marinoni, A; Bonasoni, P; Duchi, R
2011 | Atmos. Chem. Phys. | 11 (23) (12007-12036)
Scientific paper

General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

Kulmala, M; Asmi, A; Lappalainen, HK; Baltensperger, U; Brenguier, JL; Facchini, MC; Hansson, HC; Hov, O; O'Dowd, CD; Poschl, U; Wiedensohler, A; Boers, R; Boucher, O; de Leeuw, G; van der Gon, HACD; Feichter, J; Krejci, R; Laj, P; Lihavainen, H; Lohmann, U; McFiggans, G; Mentel, T; Pilinis, C; Riipinen, I; Schulz, M; Stohl, A; Swietlicki, E; Vignati, E; Alves, C; Amann, M; Ammann, M; Arabas, S; Artaxo, P; Baars, H; Beddows, DCS; Bergstrom, R; Beukes, JP; Bilde, M; Burkhart, JF; Canonaco, F; Clegg, SL; Coe, H; Crumeyrolle, S; D'Anna, B; Decesari, S; Gilardoni, S; Fischer, M; Fjaeraa, AM; Fountoukis, C; George, C; Gomes, L; Halloran, P; Hamburger, T; Harrison, RM; Herrmann, H; Hoffmann, T; Hoose, C; Hu, M; Hyvarinen, A; Horrak, U; Iinuma, Y; Iversen, T; Josipovic, M; Kanakidou, M; Kiendler-Scharr, A; Kirkevag, A; Kiss, G; Klimont, Z; Kolmonen, P; Komppula, M; Kristjansson, JE; Laakso, L; Laaksonen, A; Labonnote, L; Lanz, VA; Lehtinen, KEJ; Rizzo, LV; Makkonen, R; Manninen, HE; McMeeking, G; Merikanto, J; Minikin, A; Mirme, S; Morgan, WT; Nemitz, E; O'Donnell, D; Panwar, TS; Pawlowska, H; Petzold, A; Pienaar, JJ; Pio, C; Plass-Duelmer, C; Prevot, ASH; Pryor, S; Reddington, CL; Roberts, G; Rosenfeld, D; Schwarz, J; Seland, O; Sellegri, K; Shen, XJ; Shiraiwa, M; Siebert, H; Sierau, B; Simpson, D; Sun, JY; Topping, D; Tunved, P; Vaattovaara, P; Vakkari, V; Veefkind, JP; Visschedijk, A; Vuollekoski, H; Vuolo, R; Wehner, B; Wildt, J; Woodward, S; Worsnop, DR; van Zadelhoff, GJ; Zardini, AA; Zhang, K; van Zyl, PG; Kerminen, VM; Carslaw, KS; Pandis, SN
2011 | Atmos. Chem. Phys. | 11 (24) (13061-13143)
atmospheric sulfuric-acid , chemical-transport model , ion-induced nucleation , mixed-phase clouds , nuclei number concentration , particle formation events , pure component properties , saturation vapor-pressures , secondary organic aerosol , simulation chamber saphir

In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.

Scientific paper

Measured Elemental Carbon by Thermo-Optical Transmittance Analysis in Water-Soluble Extracts from Diesel Exhaust, Woodsmoke, and Ambient Particulate Samples

Wallén, A.; Lidén, G.; Hansson, H.-C.
2010 | J Occup Environ Hyg | 7 (1) (35-45)
combustion , niosh method 5040 , occupational exposure , residential woodburning

Elemental carbon has been proposed as a marker of diesel particulate matter. The objective of this study was to investigate if water-soluble carbonaceous compounds could be responsible for positive bias of elemental carbon using NIOSH Method 5040 with a thermo-optical carbon transmittance analyzer. Filter samples from eight different aerosol environments were used: pure diesel exhaust fume with a high content of elemental carbon, pure diesel exhaust fume with a low content of elemental carbon, pure biodiesel exhaust fume, pure woodsmoke, an urban road tunnel, an urban street canyon, an urban background site, and residential woodburning in an urban area. Part of each filter sample was analyzed directly with a thermo-optical carbon analyzer, and another part was extracted with water. This water-soluble extract was filtered to remove particles, spiked onto filter punches, and analyzed with a thermo-optical transmittance carbon analyzer. The ratio of elemental carbon in the watersoluble extract to the particulate sample measurement was 18, 12, and 7%, respectively, for the samples of pure woodsmoke, residential woodburning, and urban background. Samples with diesel particulate matter and ambient samples with motor exhaust detected no elemental carbon in the water-soluble extract. Since no particles were present in the filtered watersoluble extract, part of the water-soluble organic carbon species, existing or created during analysis, are misclassified as elemental carbon with this analysis. The conclusion is that in measuring elemental carbon in particulate aerosol samples with thermo-optical transmittance analysis, woodsmoke, and biomass combustion samples show a positive bias of elemental carbon. The water-soluble EC could be used as a simple method to indicate other sources, such as wood or other biomass combustion aerosol particles.

Scientific paper

Time span and spatial scale of regional new particle formation events over Finland and Southern Sweden

Hussein, T.; Junninen, H.; Tunved, P.; Kristensson, A.; Dal Maso, M.; Riipinen, I.; Aalto, P.P.; Hansson, H.-C.; Swietlicki, E.; Kulmala, M.
2009 | Atmos. Chem. Phys. | 9 (14) (4699-4716)
aerosol formation , air-mass history , atmosphere , back trajectories analysis , continental boundary-layer , evolution , growth , nucleation events , number size distributions , smear-ii

We investigated the time span and spatial scale of regional new particle formation (NPF) events in Finland and Southern Sweden using measured particle number size distributions at five background stations. We define the time span of a NPF event as the time period from the first moment when the newly formed mode of aerosol particles is observable below 25 nm until the newly formed mode is not any more distinguishable from other background modes of aerosol particles after growing to bigger sizes. We identify the spatial scale of regional NPF events based on two independent approaches. The first approach is based on the observation within a network of stationary measurement stations and the second approach is based on the time span and the history of air masses back-trajectories. According to the second approach, about 60% and 28% of the events can be traced to distances longer than 220 km upwind from where the events were observed in Southern Finland (Hyytiala) and Northern Finland (Varrio), respectively. The analysis also showed that the observed regional NPF events started over the continents but not over the Atlantic Ocean. The first approach showed that although large spatial scale NPF events are frequently observed at several locations simultaneously, they are rarely identical (similar characteristics and temporal variations) due to differences in the initial meteorological and geographical conditions between the stations. The growth of the newly formed particles during large spatial scale events can be followed for more than 30 h where the newly formed aerosol particles end up in the Aitken mode (diameter 25-100 nm) and accumulation mode size ranges (diameter 0.1-1 mu m). This study showed clear evidence that regional NPF events can pose a significant source for accumulation mode particles over the Scandinavian continent provided that these findings can be generalized to many of the air masses traveling over the European continent.

Scientific paper

Introduction: European Integrated Project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales (vol 9, pg 2825, 2009)

Kulmala, M.; Asmi, A.; Lappalainen, H.K.; Carslaw, K.S.; Poschl, U.; Baltensperger, U.; Hov, O.; Brenguier, J.L.; Pandis, S.N.; Facchini, M.C.; Hansson, H.-C.; Wiedensohler, A.; O'Dowd, C.D.
2009 | Atmos. Chem. Phys. | 9 (10) (3443-3444)
Scientific paper

Introduction: European Integrated Project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

Kulmala, M.; Asmi, A.; Lappalainen, H.K.; Carslaw, K.S.; Poschl, U.; Baltensperger, U.; Hov, O.; Brenquier, J.L.; Pandis, S.N.; Facchini, M.C.; Hansson, H.-C.; Wiedensohler, A.; O'Dowd, C.D.
2009 | Atmos. Chem. Phys. | 9 (8) (2825-2841)
ccn activity , droplet growth-kinetics , gas-particle interactions , kinetic-model framework , mass-spectra , nucleation , pollution , source attribution , submicron organic aerosols , surface-chemistry

The European Aerosol Cloud Climate and Air Quality Interactions project EUCAARI is an EU Research Framework 6 integrated project focusing on understanding the interactions of climate and air pollution. EUCAARI works in an integrative and multidisciplinary way from nano-to global scale. EUCAARI brings together several leading European research groups, state-of-the-art infrastructure and some key scientists from third countries to investigate the role of aerosol on climate and air quality. Altogether 48 partners from 25 countries are participating in EUCAARI. During the first 16 months EUCAARI has built operational systems, e. g. established pan-European measurement network for Lagrangian studies and four stations in developing countries. Also an improved understanding of nanoscale processes (like nucleation) has been implemented in global models. Here we present the research methods, organisation, operations and first results of EUCAARI.

Scientific paper

The Cloud Condensation Nuclei (CCN) properties of 2-methyltetrols and C3-C6 polyols from osmolality and surface tension measurements

Ekström, S.; Nozière, B.; Hansson, H.-C.
2009 | Atmos. Chem. Phys. | 9 (3) (973-980)
activation , amazon basin , isoprene , mass spectrometry , organic aerosol fraction , particle phase , photooxidation , products , soluble organics , sulfate

A significant fraction of the organic material in aerosols is made of highly soluble compounds such as sugars (mono-and polysaccharides) and polyols such as the 2-methyltetrols, methylerythritol and methyltreitol. Because of their high solubility these compounds are considered as potentially efficient CCN material. For the 2-methyltetrols, this would have important implications for cloud formation at global scale because they are thought to be produced by the atmospheric oxidation of isoprene. To investigate this question, the complete Kohler curves for C3-C6 polyols and the 2-methyltetrols have been determined experimentally from osmolality and surface tension measurements. Contrary to what was expected, none of these compounds displayed a higher CCN efficiency than organic acids. Their Raoult terms show that this limited CCN efficiency is due to their absence of dissociation in water, this in spite of slight surface-tension effects for the 2-methyltetrols. Thus, compounds such as saccharides and polyols would not contribute more to cloud formation than other organic compounds studied so far. In particular, the presence of 2-methyltetrols in aerosols would not particularly enhance cloud formation in the atmosphere, in contrary to recently suggested.

Scientific paper

Overview of the biosphere-aerosol-cloud-climate interactions (BACCI) studies

Kulmala, M.; Kerminen, V.M.; Laaksonen, A.; Riipinen, I.; Sipila, M.; Ruuskanen, T.M.; Sogacheva, L.; Hari, P.; Back, J.; Lehtinen, K.E.J.; Viisanen, Y.; Bilde, M.; Svenningsson, B.; Lazaridis, M.; Torseth, K.; Tunved, P.; Nilsson, E. D.; Pryor, S.; Sorensen, L.L.; Horrak, U.; Winkler, P.M.; Swietlicki, E.; Riekkola, M.L.; Krejci, R.; Hoyle, C.; Hov, O.; Myhre, G.; Hansson, H.-C.
2008 | Tellus B Chem Phys Meteorol | 60 (3) (300-317)
atmospheric sulfuric-acid , boreal forest , condensation nuclei , critical supersaturations , evaporation rates , global aerosol , nucleation mode particles , saturation vapor-pressures , size distribution

Here we present research methods and results obtained by the Nordic Centre of Excellence Biosphere-Aerosol-Cloud-Climate Interactions (BACCI) between 1 January 2003 and 31 December 2007. The centre formed an integrated attempt to understand multiple, but interlinked, biosphere-atmosphere interactions applying inter and multidisciplinary approaches in a coherent manner. The main objective was to study the life cycle of aerosol particles and their importance on climate change. The foundation in BACCI was a thorough understanding of physical, meteorological, chemical and ecophysiological processes, providing a unique possibility to study biosphere-aerosol-cloud-climate interactions. Continuous measurements of atmospheric concentrations and fluxes of aerosol particles and precursors and, CO2/aerosol trace gas interactions in different field stations (e.g. SMEAR) were supported by models of particle thermodynamics, transport and dynamics, atmospheric chemistry, boundary layer meteorology and forest growth. The main progress was related to atmospheric new particle formation, existence of clusters, composition of nucleation mode aerosol particles, chemical precursors of fresh aerosol particles, the contribution of biogenic aerosol particles on the global aerosol load, transport, transformation and deposition of aerosol particles, thermodynamics related to aerosol particles and cloud droplets, and the microphysics and chemistry of cloud droplet formation.

Scientific paper

Hygroscopic properties of submicrometer atmospheric aerosol particles measured with H-TDMA instruments in various environments – a review

Swietlicki, E.; Hansson, H.-C.; Hameri, K.; Svenningsson, B.; Massling, A.; McFiggans, G.; McMurry, P.H.; Petaja, T.; Tunved, P.; Gysel, M.; Topping, D.; Weingartner, E.; Baltensperger, U.; Rissler, J.; Wiedensohler, A.; Kulmala, M.
2008 | Tellus B Chem Phys Meteorol | 60 (3) (432-469)
amazon rain-forest , ammonium-sulfate , differential mobility analyzer , growth measurements , nucleation mode , organic compounds , sea salt , size distribution , soluble volume fraction , water activities

The hygroscopic properties play a vital role for the direct and indirect effects of aerosols on climate, as well as the health effects of particulate matter (PM) by modifying the deposition pattern of inhaled particles in the humid human respiratory tract. Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA) instruments have been used in field campaigns in various environments globally over the last 25 yr to determine the water uptake on submicrometre particles at subsaturated conditions. These investigations have yielded valuable and comprehensive information regarding the particle hygroscopic properties of the atmospheric aerosol, including state of mixing. These properties determine the equilibrium particle size at ambient relative humidities and have successfully been used to calculate the activation of particles at water vapour supersaturation. This paper summarizes the existing published H-TDMA results on the size-resolved submicrometre aerosol particle hygroscopic properties obtained from ground-based measurements at multiple marine, rural, urban and free tropospheric measurement sites. The data is classified into groups of hygroscopic growth indicating the external mixture, and providing clues to the sources and processes controlling the aerosol. An evaluation is given on how different chemical and physical properties affect the hygroscopic growth.

Scientific paper

Factors affecting non-tailpipe aerosol particle emissions from paved roads: On-road measurements in Stockholm, Sweden

Hussein, T.; Johansson, C.; Karlsson, H.; Hansson, H.-C.
2008 | Atmos. Environ. | 42 (4) (688-702)
finland , impact , model , number concentrations , particle size distribution , particulate matter , pm10 , re-suspension , resuspended dust , road dust , road wears road traffic , tire wear , traker , unpaved roads , urban

A large fraction of urban PM10 concentrations is due to non-exhaust traffic emissions. In this paper, a mobile measurement system has been used to quantify the relative importance of road particle emission and suspension of accumulated dust versus direct pavement wear, tire type (studded, friction, and summer), pavement type, and vehicle speed. Measurements were performed during May-September on selected roads with different pavements and traffic conditions in the Stockholm region. The highest particle mass concentrations were always observed behind the studded tire and the lowest were behind the summer tire; studded-to-summer ratios were 4.4-17.3 and studded-to-friction ratios were 2.0-6.4. This indicates that studded tires lead to higher emissions than friction and summer tires regardless to the asphalt type. By comparing with measurements in a road simulator, it could be estimated that the pavement wear due to the friction tires was 0.018-0.068 of the suspension of accumulated road dust. Likewise for studded tires road-wear was estimated to be 1.2-4.8 the suspension of accumulated dust. This indicates that wear due to friction tires is very small compared to the suspension of accumulated dust and that suspension due to studded tires may sometimes be as large as the wear of the road. But this will vary depending on, e.g. the amount of dust accumulated on the roads. An important dependence on vehicle speed was also observed. During May, the particle mass concentrations behind the studded tire at vehicle speed 100 km h(-1) were about 10 times higher than that at 20 km h(-1). The speed dependence was not so pronounced in September, which could be due to less accumulated dust on the roads. The particle number size distribution of the emissions due to road wear by studded tire was characterized by a clear increase in number concentrations of the coarse fraction of aerosol particles, with a geometric mean diameter between 3 and 5 mu m. The size distribution of the emissions due to the summer tire was very similar with smaller concentrations. An important limitation with the measurements presented is that they were made by using a van, which is bigger than regular cars and has bigger tires. Thus, road wear and dust suspension due to cars are expected to be different. (C) 2007 Elsevier Ltd. All rights reserved.

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