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2. Cantilever-enhanced photoacoustic measurement of light-absorbing aerosols

Author

Karhu, Juho, Kuula, Joel, Virkkula, Aki, Timonen, Hilkka, Vainio, Markku, and Hieta, Tuomas

Subjects
Physics - Instrumentation and Detectors, Physics - Atmospheric and Oceanic Physics
Abstract

Photoacoustic detection is a sensitive method for measurement of light-absorbing particles directly in the aerosol phase. In this article, we demonstrate a new sensitive technique for photoacoustic aerosol absorption measurements using a cantilever microphone for the detection of the photoacoustic signal. Compared to conventional diaphragm microphones, a cantilever offers increased sensitivity by up to two orders of magnitude. Here we reached a noise level of 0.013 Mm$^{-1}$ (one standard deviation) with a sampling time of 20 s, using a simple single-pass design without a need for a resonant acoustic cell. We demonstrate the method in measurements of size-selected nigrosin particles and ambient black carbon. Due to the exceptional sensitivity, the technique shows great potential for applications where low detection limits are required, for example size-selected absorption measurements and black carbon detection in ultra clean environments., Comment: 18 pages, 6 figures

Published
2021

7. Multiple eco-regions contribute to the seasonal cycle of Antarctic aerosol size distributions.

Author

Brean, James, Beddows, David C. S., Asmi, Eija, Virkkula, Aki, Quéléver, Lauriane L. J., Sipilä, Mikko, Van Den Heuvel, Floortje, Lachlan-Cope, Thomas, Jones, Anna E., Frey, Markus, Lupi, Angelo, Park, Jiyeon, Young Jun Yoon, Weller, Rolf, Marincovich, Giselle L., Mulena, Gabriela C., Harrison, Roy M., and Dall'Osto, Manuel

Abstract

In order to reduce the uncertainty of aerosol radiative forcing in global climate models, we need to better understand natural aerosol sources which are important to constrain the current and pre-industrial climate. Here, we analyze Particle Number Size Distributions (PNSD) collected during a year (2015) across four coastal and inland Antarctic research bases (Halley, Marambio, Concordia/Dome C and King Sejong). We find that the four Antarctic locations have striking differences in PNSD, stressing multiple aerosol sources and processes likely exist. We utilise k-means cluster analysis to separate the PNSD data into six main categories. Nucleation and Bursting PNSDs occur 28-48% of the time between sites, most commonly at coastal sites Marambio and King Sejong where air masses mostly come from the west and travel over extensive regions of sea ice, marginal ice, and open ocean, and likely arise from new particle formation. Aitken high, Aitken low, and bimodal PNSDs occur 37-68% of the time, most commonly at Concordia/Dome C on the Antarctic Plateau, and likely arise from atmospheric transport and aging from aerosol originating likely in both coastal boundary layer and free troposphere. Pristine PNSDs with low aerosol concentrations occur 12-45% of the time, most common at Halley located at low altitudes and far from the coastal melting ice, and influenced by air masses from the west. The Antarctic Atmospheric circulation has a strong control on the air mass origin type. Most of the time Marambio and King Sejong stations are affected by Easterly air masses, whereas Halley gets air masses mainly from the Weddell sea marginal and consolidated pack ice. Not only the sea spray primary aerosols and gas to particle secondary aerosols sources, but also the different air masses impacting the research stations should be kept in mind when deliberating upon different aerosol precursors sources across research stations. We provide evidence that both primary and secondary components from pelagic and sympagic regions strongly contribute to the annual seasonal cycle of Antarctic aerosols which add insight on the possible sources of aerosol production/activity in the whole Antarctic region. Our simultaneous aerosol measurements stress the importance of the variation in atmospheric biogeochemistry across the Antarctic region. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Soot-on-snow experiment: artificial deposition of light-absorbing particles onto snow surfaces in 2018.

Author

Svensson, Jonas, Leppänen, Leena, Hannula, Henna-Reetta, Kontu, Anna, Shen, Yi-cheng, Meinander, Outi, Dagsson-Waldhauserová, Pavla, Mesceriakovas, Arunas, Heikkinen, Enna, Ruppel, Meri, Sippula, Olli, Ström, Johan, Asmi, Eija, Virkkula, Aki, Renard, Jean-Baptiste, and Wang, Yuying

Subjects
SPRING, PARTICLE size distribution, ALBEDO, PARTICLE analysis
Abstract

The absorption of shortwave irradiance in snow depends on the physical properties of snow (e.g., snow grain size and shape, liquid water content, etc.) and light-absorbing particles (LAP). Originating from natural and anthropogenic sources, LAP has been reported to accelerate snowmelt significantly in different regions globally. Yet, our process-level understanding of LAP after deposition onto snow remains rather limited. Here we investigate the impacts of artificial deposition of different LAP onto snow surfaces in an outdoor environment of northern Finland. Following LAP dry deposition into a custom-made tent standing on top of the snowpack, the albedo was followed along with the properties of snow in snow pit measurements throughout the spring season. The results showed that the albedo decay at the end of the season for the different spots were linked to the initial amount and type of LAP that were deposited onto the snowpack. Measured snow temperature profiles from LAP doped snow versus natural reference snow illustrated that the LAP affected snow had higher temperatures in the subsurface snow layers. Collected snow samples analyzed for size distribution of soot particles revealed no apparent agglomeration of soot particles during thaw-freezing events taking place during the experiment. Despite the relatively large perturbation of the experimentally deposited LAP, their impact on the season length was only up to 3 days. Additional experiments are, nevertheless, needed to better constrain the effects of LAP on snow albedo, melt rate, and other associated processes. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Contribution of brown carbon to light absorption in emissions of European residential biomass combustion appliances.

Author

Basnet, Satish, Hartikainen, Anni, Virkkula, Aki, Yli-Pirilä, Pasi, Kortelainen, Miika, Suhonen, Heikki, Kilpeläinen, Laura, Ihalainen, Mika, Väätäinen, Sampsa, Louhisalmi, Juho, Somero, Markus, Tissari, Jarkko, Jakobi, Gert, Zimmermann, Ralf, Kilpeläinen, Antti, and Sippula, Olli

Subjects
BIOMASS burning, LIGHT absorption, WOOD combustion, CARBONACEOUS aerosols, COMBUSTION efficiency, WOOD stoves, CO-combustion, COAL combustion
Abstract

Residential biomass combustion significantly contributes to light-absorbing carbonaceous aerosols in the atmosphere, impacting the earth's radiative balance at regional and global levels. This study investigates the contribution of brown carbon (BrC) to the total particulate light absorption in the wavelength range of 370–950 nm (BrC 370–950) and the particulate absorption Ångström exponents (AAE 470/950) in 15 different European residential combustion appliances using a variety of wood-based fuels. BrC 370–950 was estimated to be from 1 % to 21 % for wood log stoves and 10 % for a fully automatized residential pellet boiler. Correlations between the ratio of organic to elemental carbon (OC / EC) and BrC 370–950 indicated that a one-unit increase in OC / EC corresponded to approximately a 14 % increase in BrC 370–950. Additionally, BrC 370–950 was clearly influenced by the fuel moisture content and the combustion efficiency, while the effect of the combustion appliance type was less prominent. AAE 470/950 of wood log combustion aerosols ranged from 1.06 to 1.61. By examining the correlation between AAE 470/950 and OC / EC, an AAE 470/950 close to unity was found for pure black carbon (BC) particles originating from residential wood combustion. This supports the common assumption used to differentiate light absorption caused by BC and BrC. Moreover, diesel aerosols exhibited an AAE 470/950 of 1.02, with BrC contributing only 0.66 % to the total absorption, aligning with the assumption employed in source apportionment. These findings provide important data to assess the BrC from residential wood combustion with different emission characteristics and confirm that BrC can be a major contributor to particulate UV and near-UV light absorption for northern European wood stove emissions with relatively high OC / EC ratios. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Contribution of brown carbon on light absorption in emissions of European residential biomass combustion appliances

Author

Basnet, Satish, primary, Hartikainen, Anni, additional, Virkkula, Aki, additional, Yli-Pirilä, Pasi, additional, Kortelainen, Miika, additional, Suhonen, Heikki, additional, Kilpeläinen, Laura, additional, Ihalainen, Mika, additional, Väätäinen, Sampsa, additional, Louhisalmi, Juho, additional, Somero, Markus, additional, Tissari, Jarkko, additional, Jakobi, Gert, additional, Zimmermann, Ralf, additional, Kilpeläinen, Antti, additional, and Sippula, Olli, additional

Published
2023
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11. Supplementary material to "Contribution of brown carbon on light absorption in emissions of European residential biomass combustion appliances"

Author

Basnet, Satish, primary, Hartikainen, Anni, additional, Virkkula, Aki, additional, Yli-Pirilä, Pasi, additional, Kortelainen, Miika, additional, Suhonen, Heikki, additional, Kilpeläinen, Laura, additional, Ihalainen, Mika, additional, Väätäinen, Sampsa, additional, Louhisalmi, Juho, additional, Somero, Markus, additional, Tissari, Jarkko, additional, Jakobi, Gert, additional, Zimmermann, Ralf, additional, Kilpeläinen, Antti, additional, and Sippula, Olli, additional

Published
2023
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14. Photochemical Aging Induces Changes in the Effective Densities, Morphologies, and Optical Properties of Combustion Aerosol Particles

Author

Leskinen, Jani, primary, Hartikainen, Anni, additional, Väätäinen, Sampsa, additional, Ihalainen, Mika, additional, Virkkula, Aki, additional, Mesceriakovas, Arunas, additional, Tiitta, Petri, additional, Miettinen, Mirella, additional, Lamberg, Heikki, additional, Czech, Hendryk, additional, Yli-Pirilä, Pasi, additional, Tissari, Jarkko, additional, Jakobi, Gert, additional, Zimmermann, Ralf, additional, and Sippula, Olli, additional

Published
2023
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15. INTERNATIONAL ARCTIC SYSTEMS FOR OBSERVING THE ATMOSPHERE : An International Polar Year Legacy Consortium

Author

Uttal, Taneil, Starkweather, Sandra, Drummond, James R., Vihma, Timo, Makshtas, Alexander P., Darby, Lisa S., Burkhart, John F., Cox, Christopher J., Schmeisser, Lauren N., Haiden, Thomas, Maturilli, Marion, Shupe, Matthew D., de Boer, Gijs, Saha, Auromeet, Grachev, Andrey A., Crepinsek, Sara M., Bruhwiler, Lori, Goodison, Barry, McArthur, Bruce, Walden, Von P., Dlugokencky, Edward J., Persson, P. Ola G., Lesins, Glen, Laurila, Tuomas, Ogren, John A., Stone, Robert, Long, Charles N., Sharma, Sangeeta, Massling, Andreas, Turner, David D., Stanitski, Diane M., Asmi, Eija, Aurela, Mika, Skov, Henrik, Eleftheriadis, Konstantinos, Virkkula, Aki, Platt, Andrew, Førland, Eirik J., Iijima, Yoshihiro, Nielsen, Ingeborg E., Bergin, Michael H., Candlish, Lauren, Zimov, Nikita S., Zimov, Sergey A., O’Neill, Norman T., Fogal, Pierre F., Kivi, Rigel, Konopleva-Akish, Elena A., Verlinde, Johannes, Kustov, Vasily Y., Vasel, Brian, Ivakhov, Viktor M., Viisanen, Yrjö, and Intrieri, Janet M.

Published
2016

16. Contribution of brown carbon on light absorption in emissions of European residential biomass combustion appliances.

Author

Basnet, Satish, Hartikainen, Anni, Virkkula, Aki, Yli-Pirilä, Pasi, Kortelainen, Miika, Suhonen, Heikki, Kilpeläinen, Laura, Ihalainen, Mika, Väätäinen, Sampsa, Louhisalmi, Juho, Somero, Markus, Tissari, Jarkko, Jakobi, Gert, Zimmermann, Ralf, Kilpeläinen, Antti, and Sippula, Olli

Subjects
CARBONACEOUS aerosols, BIOMASS burning, LIGHT absorption, WOOD combustion, COMBUSTION efficiency, WOOD stoves
Abstract

Residential biomass combustion significantly contributes to light-absorbing carbonaceous aerosols in the atmosphere, impacting the Earth's radiative balance at regional and global levels. This study investigates the contribution of brown carbon to the total particulate light absorption in the wavelength range of 370 to 950 nm (BrC370-950)and the particulate absorption Ångström exponents (AAE470/950) in 15 different European residential combustion appliances using a variety of wood-based fuels. BrC370-950 was estimated to be from 1 % to 21 % for wood log stoves and was primarily influenced by fuel moisture content and minimally affected by combustion appliance type. The BrC370-950 contribution was 10 % for a fully automatized residential pellet boiler. Correlations between the ratio of organic to elemental carbon (OC/EC) and BrC indicated that a one unit increase in OC/EC corresponded to approximately a 14 % increase in BrC370-950. Additionally, BrC370-950 increased with decreasing combustion efficiency. AAE470/950 of wood log combustion aerosols ranged from 1.06 to 1.61. By examining the correlation between AAE470/950 and OC/EC, an AAE470/950 close to unity was found for pure black carbon (BC) particles originating from residential wood combustion. This supports the common assumption used to differentiate light absorption caused by BC and BrC. Moreover, diesel aerosols exhibited an AAE470/950 of 1.02, with BrC370-950 contributing only 0.66 % to the total absorption, aligning with the assumption employed in source apportionment. These findings provide important data to assess the BrC370-950 of RWC emissions with different emission characteristics and confirm that BrC can be a major contributor to particulate UV and near-UV light absorption for Northern European wood stove emissions with relatively high OC/EC ratios. [ABSTRACT FROM AUTHOR]

Published
2023
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20. Tropical and Boreal Forest Atmosphere Interactions : A Review

Author

Artaxo, Paulo, Hansson, Hans-Christen, Andreae, Meinrat O., Bäck, Jaana, Alves, Eliane Gomes, Barbosa, Henrique M. J., Bender, Frida, Bourtsoukidis, Efstratios, Carbone, Samara, Chi, Jinshu, Decesari, Stefano, Despres, Viviane R., Ditas, Florian, Ezhova, Ekaterina, Fuzzi, Sandro, Hasselquist, Niles J., Heintzenberg, Jost, Holanda, Bruna A., Guenther, Alex, Hakola, Hannele, Heikkinen, Liine, Kerminen, Veli-Matti, Kontkanen, Jenni, Krejci, Radovan, Kulmala, Markku, Lavric, Jost, de Leeuw, Gerrit, Lehtipalo, Katrianne, Machado, Luiz Augusto T., McFiggans, Gordon, Franco, Marco Aurelio M., Meller, Bruno Backes, Morais, Fernando G., Mohr, Claudia, Morgan, William, Nilsson, Mats B., Peichl, Matthias, Petäjä, Tuukka, Prass, Maria, Poehlker, Christopher, Poehlker, Mira L., Poeschl, Ulrich, Von Randow, Celso, Riipinen, Ilona, Rinne, Janne, Rizzo, Luciana, Rosenfeld, Daniel, Silva Dias, Maria A. F., Sogacheva, Larisa, Stier, Philip, Swietlicki, Erik, Soergel, Matthias, Tunved, Peter, Virkkula, Aki, Wang, Jian, Weber, Bettina, Maria Yanez-Serrano, Ana, Zieger, Paul, Mikhailov, Eugene, Smith, James N., Kesselmeier, Juergen, Viikki Plant Science Centre (ViPS), Department of Forest Sciences, Forest Ecology and Management, Ecosystem processes (INAR Forest Sciences), Institute for Atmospheric and Earth System Research (INAR), University of Helsinki, Global Atmosphere-Earth surface feedbacks, Department of Physics, and Air quality research group

Subjects
biomass burning, 4112 Forestry, Tropical forests, aerosol particles, LONG-TERM MEASUREMENTS, LAND-USE CHANGE, NUCLEATION-MODE PARTICLES, PRIMARY BIOLOGICAL AEROSOL, TOWER OBSERVATORY ZOTTO, 114 Physical sciences, AMAZON RAIN-FOREST, CLOUD CONDENSATION NUCLEI, Boreal forests, Amazonia, SECONDARY ORGANIC AEROSOL, BIOMASS BURNING AEROSOLS, INTERTROPICAL CONVERGENCE ZONE, biogenic emissions: fires, climate effects
Abstract

This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiala in Finland. The review is complemented by short-term observations from networks and large experiments. The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction. Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink. It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.

Published
2022

21. Aerosol optical properties calculated from size distributions, filter samples and absorption photometer data at Dome C, Antarctica, and their relationships with seasonal cycles of sources

Author

Virkkula, Aki, primary, Grythe, Henrik, additional, Backman, John, additional, Petäjä, Tuukka, additional, Busetto, Maurizio, additional, Lanconelli, Christian, additional, Lupi, Angelo, additional, Becagli, Silvia, additional, Traversi, Rita, additional, Severi, Mirko, additional, Vitale, Vito, additional, Sheridan, Patrick, additional, and Andrews, Elisabeth, additional

Published
2022
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22. Overview: Recent advances in the understanding of the northern Eurasian environments and of the urban air quality in China – a Pan-Eurasian Experiment (PEEX) programme perspective

Author

Lappalainen, Hanna K., primary, Petäjä, Tuukka, additional, Vihma, Timo, additional, Räisänen, Jouni, additional, Baklanov, Alexander, additional, Chalov, Sergey, additional, Esau, Igor, additional, Ezhova, Ekaterina, additional, Leppäranta, Matti, additional, Pozdnyakov, Dmitry, additional, Pumpanen, Jukka, additional, Andreae, Meinrat O., additional, Arshinov, Mikhail, additional, Asmi, Eija, additional, Bai, Jianhui, additional, Bashmachnikov, Igor, additional, Belan, Boris, additional, Bianchi, Federico, additional, Biskaborn, Boris, additional, Boy, Michael, additional, Bäck, Jaana, additional, Cheng, Bin, additional, Chubarova, Natalia, additional, Duplissy, Jonathan, additional, Dyukarev, Egor, additional, Eleftheriadis, Konstantinos, additional, Forsius, Martin, additional, Heimann, Martin, additional, Juhola, Sirkku, additional, Konovalov, Vladimir, additional, Konovalov, Igor, additional, Konstantinov, Pavel, additional, Köster, Kajar, additional, Lapshina, Elena, additional, Lintunen, Anna, additional, Mahura, Alexander, additional, Makkonen, Risto, additional, Malkhazova, Svetlana, additional, Mammarella, Ivan, additional, Mammola, Stefano, additional, Buenrostro Mazon, Stephany, additional, Meinander, Outi, additional, Mikhailov, Eugene, additional, Miles, Victoria, additional, Myslenkov, Stanislav, additional, Orlov, Dmitry, additional, Paris, Jean-Daniel, additional, Pirazzini, Roberta, additional, Popovicheva, Olga, additional, Pulliainen, Jouni, additional, Rautiainen, Kimmo, additional, Sachs, Torsten, additional, Shevchenko, Vladimir, additional, Skorokhod, Andrey, additional, Stohl, Andreas, additional, Suhonen, Elli, additional, Thomson, Erik S., additional, Tsidilina, Marina, additional, Tynkkynen, Veli-Pekka, additional, Uotila, Petteri, additional, Virkkula, Aki, additional, Voropay, Nadezhda, additional, Wolf, Tobias, additional, Yasunaka, Sayaka, additional, Zhang, Jiahua, additional, Qiu, Yubao, additional, Ding, Aijun, additional, Guo, Huadong, additional, Bondur, Valery, additional, Kasimov, Nikolay, additional, Zilitinkevich, Sergej, additional, Kerminen, Veli-Matti, additional, and Kulmala, Markku, additional

Published
2022
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23. Tropical and Boreal Forest – Atmosphere Interactions: A Review

Author

Artaxo, Paulo, primary, Hansson, Hans-Christen, additional, Andreae, Meinrat O., additional, Bäck, Jaana, additional, Alves, Eliane Gomes, additional, Barbosa, Henrique M. J., additional, Bender, Frida, additional, Bourtsoukidis, Efstratios, additional, Carbone, Samara, additional, Chi, Jinshu, additional, Decesari, Stefano, additional, Després, Viviane R., additional, Ditas, Florian, additional, Ezhova, Ekaterina, additional, Fuzzi, Sandro, additional, Hasselquist, Niles J., additional, Heintzenberg, Jost, additional, Holanda, Bruna A., additional, Guenther, Alex, additional, Hakola, Hannele, additional, Heikkinen, Liine, additional, Kerminen, Veli-Matti, additional, Kontkanen, Jenni, additional, Krejci, Radovan, additional, Kulmala, Markku, additional, Lavric, Jost V., additional, De Leeuw, Gerrit, additional, Lehtipalo, Katrianne, additional, Machado, Luiz Augusto T., additional, McFiggans, Gordon, additional, Franco, Marco Aurelio M., additional, Meller, Bruno Backes, additional, Morais, Fernando G., additional, Mohr, Claudia, additional, Morgan, William, additional, Nilsson, Mats B., additional, Peichl, Matthias, additional, Petäjä, Tuukka, additional, Praß, Maria, additional, Pöhlker, Christopher, additional, Pöhlker, Mira L., additional, Pöschl, Ulrich, additional, Von Randow, Celso, additional, Riipinen, Ilona, additional, Rinne, Janne, additional, Rizzo, Luciana V., additional, Rosenfeld, Daniel, additional, Silva Dias, Maria A. F., additional, Sogacheva, Larisa, additional, Stier, Philip, additional, Swietlicki, Erik, additional, Sörgel, Matthias, additional, Tunved, Peter, additional, Virkkula, Aki, additional, Wang, Jian, additional, Weber, Bettina, additional, Yáñez-Serrano, Ana Maria, additional, Zieger, Paul, additional, Mikhailov, Eugene, additional, Smith, James N., additional, and Kesselmeier, Jürgen, additional

Published
2022
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26. Effects of different correction algorithms on absorption coefficient - a comparison of three optical absorption photometers at a boreal forest site

Author

Luoma, Krista, Virkkula, Aki, Aalto, Pasi, Lehtipalo, Katrianne, Petäjä, Tuukka, Kulmala, Markku, Institute for Atmospheric and Earth System Research (INAR), Department of Physics, and Doctoral Programme in Atmospheric Sciences

Subjects
CALIBRATION, 3-WAVELENGTH, SOURCE APPORTIONMENT, FILTER-BASED MEASUREMENTS, AEROSOL LIGHT-ABSORPTION, BLACK CARBON, PARTICLES, AETHALOMETER, PERFORMANCE, AMBIENT AEROSOLS, 114 Physical sciences
Abstract

We present a comparison between three absorption photometers that measured the absorption coefficient (σabs) of ambient aerosol particles in 2012–2017 at SMEAR II (Station for Measuring Ecosystem–Atmosphere Relations II), a measurement station located in a boreal forest in southern Finland. The comparison included an Aethalometer (AE31), a multi-angle absorption photometer (MAAP), and a particle soot absorption photometer (PSAP). These optical instruments measured particles collected on a filter, which is a source of systematic errors, since in addition to the particles, the filter fibers also interact with light. To overcome this problem, several algorithms have been suggested to correct the AE31 and PSAP measurements. The aim of this study was to research how the different correction algorithms affected the derived optical properties. We applied the different correction algorithms to the AE31 and PSAP data and compared the results against the reference measurements conducted by the MAAP. The comparison between the MAAP and AE31 resulted in a multiple-scattering correction factor (Cref) that is used in AE31 correction algorithms to compensate for the light scattering by filter fibers. Cref varies between different environments, and our results are applicable to a boreal environment. We observed a clear seasonal cycle in Cref, which was probably due to variations in aerosol optical properties, such as the backscatter fraction and single-scattering albedo, and also due to variations in the relative humidity (RH). The results showed that the filter-based absorption photometers seemed to be rather sensitive to the RH even if the RH was kept below the recommended value of 40 %. The instruments correlated well (R≈0.98), but the slopes of the regression lines varied between the instruments and correction algorithms: compared to the MAAP, the AE31 underestimated σabs only slightly (the slopes varied between 0.96–1.00) and the PSAP overestimated σabs only a little (the slopes varied between 1.01–1.04 for a recommended filter transmittance >0.7). The instruments and correction algorithms had a notable influence on the absorption Ångström exponent: the median absorption Ångström exponent varied between 0.93–1.54 for the different algorithms and instruments.

Published
2021

29. Aerosol optical properties calculated from size distributions, filter samples and absorption photometer data at Dome C, Antarctica and their relationships between seasonal cycles of sources

Author

Virkkula, Aki, primary, Grythe, Henrik, additional, Backman, John, additional, Petäjä, Tuukka, additional, Busetto, Maurizio, additional, Lanconelli, Christian, additional, Lupi, Angelo, additional, Becagli, Silvia, additional, Traversi, Rita, additional, Severi, Mirko, additional, Vitale, Vito, additional, Sheridan, Patrick, additional, and Andrews, Elisabeth, additional

Published
2021
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31. Supplementary material to "Aerosol optical properties calculated from size distributions, filter samples and absorption photometer data at Dome C, Antarctica and their relationships between seasonal cycles of sources"

Author

Virkkula, Aki, primary, Grythe, Henrik, additional, Backman, John, additional, Petäjä, Tuukka, additional, Busetto, Maurizio, additional, Lanconelli, Christian, additional, Lupi, Angelo, additional, Becagli, Silvia, additional, Traversi, Rita, additional, Severi, Mirko, additional, Vitale, Vito, additional, Sheridan, Patrick, additional, and Andrews, Elisabeth, additional

Published
2021
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32. Spatiotemporal variation and trends in equivalent black carbon in the Helsinki metropolitan area in Finland

Author

Luoma, Krista, Niemi, Jarkko, Aurela, Minna, Fung, Pak Lun, Helin, Aku, Hussein, Tareq, Kangas, Leena, Kousa, Anu, Rönkkö, Topi, Timonen, Hilkka, Virkkula, Aki, Petäjä, Tuukka, Tampere University, Physics, INAR Physics, Air quality research group, Helsinki Institute of Sustainability Science (HELSUS), and Institute for Atmospheric and Earth System Research (INAR)

Subjects
114 Physical sciences
Abstract

In this study, we present results from 12 years of black carbon (BC) measurements at 14 sites around the Helsinki metropolitan area (HMA) and at one background site outside the HMA. The main local sources of BC in the HMA are traffic and residential wood combustion in fireplaces and sauna stoves. All BC measurements were conducted optically, and therefore we refer to the measured BC as equivalent BC (eBC). Measurement stations were located in different environments that represented traffic environment, detached housing area, urban background, and regional background. The measurements of eBC were conducted from 2007 through 2018; however, the times and the lengths of the time series varied at each site. The largest annual mean eBC concentrations were measured at the traffic sites (from 0.67 to 2.64 µg m−3) and the lowest at the regional background sites (from 0.16 to 0.48 µg m−3). The annual mean eBC concentrations at the detached housing and urban background sites varied from 0.64 to 0.80 µg m−3 and from 0.42 to 0.68 µg m−3, respectively. The clearest seasonal variation was observed at the detached housing sites where residential wood combustion increased the eBC concentrations during the cold season. Diurnal variation in eBC concentration in different urban environments depended clearly on the local sources that were traffic and residential wood combustion. The dependency was not as clear for the typically measured air quality parameters, which were here NOx concentration and mass concentration of particles smaller that 2.5 µm in diameter (PM2.5). At four sites which had at least a 4-year-long time series available, the eBC concentrations had statistically significant decreasing trends that varied from −10.4 % yr−1 to −5.9 % yr−1. Compared to trends determined at urban and regional background sites, the absolute trends decreased fastest at traffic sites, especially during the morning rush hour. Relative long-term trends in eBC and NOx were similar, and their concentrations decreased more rapidly than that of PM2.5. The results indicated that especially emissions from traffic have decreased in the HMA during the last decade. This shows that air pollution control, new emission standards, and a newer fleet of vehicles had an effect on air quality.

Published
2021

34. Overview: Recent advances on the understanding of the Northern Eurasian environments and of the urban air quality in China - Pan Eurasian Experiment (PEEX) program perspective

Author

Lappalainen, Hanna, primary, Petäjä, Tuukka, additional, Vihma, Timo, additional, Räisänen, Jouni, additional, Baklanov, Alexander, additional, Chalov, Sergey, additional, Esau, Igor, additional, Ezhova, Ekaterina, additional, Leppäranta, Matti, additional, Pozdnyakov, Dmitry, additional, Pumpanen, Jukka, additional, Andreae, Meinrat O., additional, Arshinov, Michael, additional, Asmi, Eija, additional, Bai, Jianhui, additional, Bashmachnikov, Igor, additional, Belan, Boris, additional, Bianchi, Federico, additional, Biskaborn, Boris, additional, Boy, Michael, additional, Bäck, Jaana, additional, Cheng, Bin, additional, Chubarova, Natalia Ye, additional, Duplissy, Jonathan, additional, Dyukarev, Egor, additional, Eleftheriadis, Konstantinos, additional, Forsius, Martin, additional, Heimann, Martin, additional, Juhola, Sirkku, additional, Konovalov, Vladimir, additional, Konovalov, Igor, additional, Konstantinov, Pavel, additional, Koster, Kajar, additional, Lapsina, Elena, additional, Lintunen, Anna, additional, Mahura, Alexander, additional, Makkonen, Risto, additional, Malkhazova, Svetlana, additional, Mammarella, Ivan, additional, Mammola, Stefano, additional, Mazon, Stephany, additional, Meinander, Outi, additional, Mikhailov, Eugene, additional, Miles, Victoria, additional, Myslenko, Stanislav, additional, Orlov, Dimitry, additional, Paris, Jean-Daniel, additional, Pirazzini, Robertta, additional, Popovicheva, Olga, additional, Pulliainen, Jouni, additional, Rautiainen, Kimmo, additional, Sachs, Torsten, additional, Shevchenko, Vladimir, additional, Skorokhod, Andrey, additional, Stohl, Andreas, additional, Suhonen, Elli, additional, Thomson, Erik S., additional, Tsidilina, Marina, additional, Tynkkynen, Veli-Pekka, additional, Uotila, Petteri, additional, Virkkula, Aki, additional, Voropay, Nadezhda, additional, Wolf, Tobias, additional, Yasunaka, Sayaka, additional, Zhang, Jiahua, additional, Qui, Yubao, additional, Ding, Aijun, additional, Guo, Huadong, additional, Bondur, Valery, additional, Kasimov, Nikolay, additional, Zilitinkevich, Sergey, additional, Kerminen, Veli-Matti, additional, and Kulmala, Markku, additional

Published
2021
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37. A simple procedure for correcting loading effects of aethalometer data

Author

Virkkula, Aki, Makela, Timo, Hillamo, Risto, Yli-Tuomi, Tarja, Hirsikko, Anne, Hameri, Kaarle, and Koponen, Ismo K.

Subjects
Motor vehicles -- Pollution control devices, Air pollution -- Control -- Usage -- Environmental aspects, Public transportation -- Environmental aspects -- Usage, Algorithms -- Usage -- Environmental aspects, Algorithm, Environmental services industry, Environmental issues, Science and technology
Abstract

ABSTRACT A simple method for correcting for the loading effects of aethalometer data is presented. The formula [BC.sub.CORRECTED] = (1 + k x ATN) x [BC.sub.NONCORRECTED], where ATN is the [...]

Published
2007

38. On the annual variability of Antarctic aerosol size distributions at Halley research station

Author

Lachlan-Cope, Thomas, Beddows, David C.S., Brough, Neil, Jones, Anna E., Harrison, Roy M., Lupi, Angelo, Yoon, Young Jun, Virkkula, Aki, Dall'Osto, Manuel, Lachlan-Cope, Thomas, Beddows, David C.S., Brough, Neil, Jones, Anna E., Harrison, Roy M., Lupi, Angelo, Yoon, Young Jun, Virkkula, Aki, and Dall'Osto, Manuel

Abstract

The Southern Ocean and Antarctic region currently best represent one of the few places left on our planet with conditions similar to the preindustrial age. Currently, climate models have low ability to simulate conditions forming the aerosol baseline; a major uncertainty comes from the lack of understanding of aerosol size distributions and their dynamics. Contrasting studies stress that primary sea-salt aerosol can contribute significantly to the aerosol population, challenging the concept of climate biogenic regulation by new particle formation (NPF) from dimethyl sulphide marine emissions. We present a statistical cluster analysis of the physical characteristics of particle size distributions (PSD) collected at Halley (Antarctica) for the year 2015 (89 % data coverage). By applying the Hartigan-Wong k-Means method we find 8 clusters describing the entire aerosol population. Three clusters show pristine average low particle number concentrations (< 121–179 cm−3) with three main modes (30 nm, 75–95 nm, 135–160 nm) and represent 57 % of the annual PSD (up to 89–100 % during winter, 34–65 % during summer based upon monthly averages). Nucleation and Aitken mode PSD clusters dominate summer months (Sep–Jan, 59–90 %), whereas a clear bimodal distribution (43 and 134 nm, respectively, min Hoppel mode 75 nm) is seen only during the Dec–Apr period (6–21 %). Major findings of the current work include: (1) NPF and growth events originate from both the sea ice marginal zone and the Antarctic plateau, strongly suggesting multiple vertical origins, including marine boundary layer and free troposphere; (2) very low particle number concentrations are detected for a substantial part of the year (57 %), including summer (34–65 %), suggesting that the strong annual aerosol concentration cycle is driven by a short temporal interval of strong NPF events; (3) a unique pristine aerosol cluster is seen with a bimodal size distribution (75 nm and 160 nm, respectively), strongly correlatin

Published
2020

39. On the annual variability of Antarctic aerosol size distributions at Halley Research Station

Author

Ministerio de Ciencia, Innovación y Universidades (España), Natural Environment Research Council (UK), Academy of Finland, Agencia Estatal de Investigación (España), Lachlan-Cope, Thomas, Beddows, David C. S., Brough, N., Jones, Anna E., Harrison, Roy M., Lupi, Angelo, Yoon, Young Jun, Virkkula, Aki, Dall'Osto, Manuel, Ministerio de Ciencia, Innovación y Universidades (España), Natural Environment Research Council (UK), Academy of Finland, Agencia Estatal de Investigación (España), Lachlan-Cope, Thomas, Beddows, David C. S., Brough, N., Jones, Anna E., Harrison, Roy M., Lupi, Angelo, Yoon, Young Jun, Virkkula, Aki, and Dall'Osto, Manuel

Abstract

The Southern Ocean and Antarctic region currently best represent one of the few places left on our planet with conditions similar to the preindustrial age. Currently, climate models have a low ability to simulate conditions forming the aerosol baseline; a major uncertainty comes from the lack of understanding of aerosol size distributions and their dynamics. Contrasting studies stress that primary sea salt aerosol can contribute significantly to the aerosol population, challenging the concept of climate biogenic regulation by new particle formation (NPF) from dimethyl sulfide marine emissions. We present a statistical cluster analysis of the physical characteristics of particle size distributions (PSDs) collected at Halley (Antarctica) for the year 2015 (89 % data coverage; 6–209 nm size range; daily size resolution). By applying the Hartigan–Wong k-mean method we find eight clusters describing the entire aerosol population. Three clusters show pristine average low particle number concentrations (< 121–179 cm−3) with three main modes (30, 75–95 and 135–160 nm) and represent 57 % of the annual PSD (up to 89 %–100 % during winter and 34 %–65 % during summer based on monthly averages). Nucleation and Aitken mode PSD clusters dominate summer months (September–January, 59 %–90 %), whereas a clear bimodal distribution (43 and 134 nm, respectively; Hoppel minimum at mode 75 nm) is seen only during the December–April period (6 %–21 %). Major findings of the current work include: (1) NPF and growth events originate from both the sea ice marginal zone and the Antarctic plateau, strongly suggesting multiple vertical origins, including the marine boundary layer and free troposphere; (2) very low particle number concentrations are detected for a substantial part of the year (57 %), including summer (34 %–65 %), suggesting that the strong annual aerosol concentration cycle is driven by a short temporal interval of strong NPF events; (3) a unique pristine aerosol cluster is seen w

Published
2020

40. Carbonaceous Aerosol in Polar Areas: First Results and Improvements of the Sampling Strategies

Author

Caiazzo, Laura, primary, Calzolai, Giulia, additional, Becagli, Silvia, additional, Severi, Mirko, additional, Amore, Alessandra, additional, Nardin, Raffaello, additional, Chiari, Massimo, additional, Giardi, Fabio, additional, Nava, Silvia, additional, Lucarelli, Franco, additional, Pazzi, Giulia, additional, Cristofanelli, Paolo, additional, Virkkula, Aki, additional, Gambaro, Andrea, additional, Barbaro, Elena, additional, and Traversi, Rita, additional

Published
2021
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50. Amine and guanidine emissions from a boreal forest floor

Author

Hemmilä, Marja, primary, Makkonen, Ulla, additional, Virkkula, Aki, additional, Panagiotopoulou, Georgia, additional, Aalto, Juho, additional, Kulmala, Markku, additional, Petäjä, Tuukka, additional, Hakola, Hannele, additional, and Hellén, Heidi, additional

Published
2020
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