Experimental Atmospheric Physical Chemistry Group

Formation of low-volatility vapours in oxidation of organic compounds

We are interested how volatile organic compounds (VOCs) emitted from nature and human activity transform into low-volatility vapours which subsequently contribute to the formation of aerosol particles. Highly oxygenated organic compounds (HOM) is a group of compounds that form fast in autoxidation reactions of biogenic molecules but also anthropogenic aromatics. We are interested in the formation pathways in single-VOC systems but also in atmospherically relevant complex mixtures.

Chemical pathways behind aerosol production in Boreal forests 

Boreal forest is the largest terrestrial ecosystem and it is known to affect climate by producing nuclei for clouds. Trees in the forest emit organic molecules which react in the atmosphere and then condense to form aerosol particles. When particles grow, they can uptake water and form clouds affecting not only water cycle but also the Earth's radiative balance. 

Our focus is on reactions of volatile organic compounds (VOC) emitted from Boreal trees, mostly different species of spruce, pine, birch and aspen, and the formation of oxidized species - aerosol precursors. So far, our knowledge on particle formation and growth in this type of forest in based on measurements done in Europe. By conducting field measurements in Eurasian and North American Boreal zones, we aim to understand how pollution and wildfires affect atmospheric chemistry over these areas.

Temperature has a strong effect not only on VOC emissions but also on how fast molecules oxidize and how fast particles form. We are interested to understand the dependence of atmospheric processes on temperature which is relevant as seasons change but also in the future warmer climate.

Gaseous aerosol precursors over oceans

The clouds that form over oceans are very sensitive to the amount of cloud condensation nuclei (CCN) - aerosol particles that are larger than about 100nm in diameter. Sea spray is one very important contributor to CCN over oceans and is formed due to mechanical breaking of sea surface.

However, sea surface is rich in organic molecules and can also act as source of these molecules to the air above. These molecules can subsequently convert into aerosol particles. We are interested in detailed processes how sea surface organics coming from biological activity affects atmospheric composition and thereby production of aerosol particles and cloud condensation nuclei. 

Chemical ionization mass spectrometry characterisation

Recent developments in chemical ionization mass spectrometer made it possible to discover central chemical pathways to aerosol formation. Specifically, low detection limits and online sampling allows for detection of organic radicals, low-volatility vapors and molecular clusters.

However, challenges still remain in calibration for compounds where standards are unavailable. In addition, we often need to deploy several complementary ionization schemes to fully characterize the complexity of the molecules in the air. In our group, we are interested in modifying ion chemistries to detect a broader range of oxidation products and characterizing how reactions inside the instrument may provide us with additional information on the molecules we sample.

Garmash, O.; Kumar, A.; Jha, S.; Barua, S.; Hyttinen, N.; Iyer, S.; Rissanen, M. Enhanced Detection of Aromatic Oxidation Products Using NO3− Chemical Ionization Mass Spectrometry with Limited Nitric Acid. Environ. Sci.: Atmos. 2024. https://doi.org/10.1039/D4EA00087K.

Garmash, O.; Ezhova, E.; Arshinov, M.; Belan, B.; Lampilahti, A.; Davydov, D.; Räty, M.; Aliaga, D.; Baalbaki, R.; Chan, T.; Bianchi, F.; Kerminen, V.-M.; Petäjä, T.; Kulmala, M. Heatwave Reveals Potential for Enhanced Aerosol Formation in Siberian Boreal Forest. Environ. Res. Lett. 2024, 19 (1), 014047. https://doi.org/10.1088/1748-9326/ad10d5.

Okuljar, M.; Garmash, O.; Olin, M.; Kalliokoski, J.; Timonen, H.; Niemi, J. V.; Paasonen, P.; Kontkanen, J.; Zhang, Y.; Hellén, H.; Kuuluvainen, H.; Aurela, M.; Manninen, H. E.; Sipilä, M.; Rönkkö, T.; Petäjä, T.; Kulmala, M.; Dal Maso, M.; Ehn, M. Influence of Anthropogenic Emissions on the Composition of Highly Oxygenated Organic Molecules in Helsinki: A Street Canyon and Urban Background Station Comparison. Atmospheric Chemistry and Physics 2023, 23 (20), 12965–12983. https://doi.org/10.5194/acp-23-12965-2023.

Luo, Y.; Garmash, O.; Li, H.; Graeffe, F.; Praplan, A. P.; Liikanen, A.; Zhang, Y.; Meder, M.; Peräkylä, O.; Peñuelas, J.; Yáñez-Serrano, A. M.; Ehn, M. Oxidation Product Characterization from Ozonolysis of the Diterpene Ent-Kaurene. Atmospheric Chemistry and Physics 2022, 22 (8), 5619–5637. https://doi.org/10.5194/acp-22-5619-2022.

Garmash, O.; Rissanen, M. P.; Pullinen, I.; Schmitt, S.; Kausiala, O.; Tillmann, R.; Zhao, D.; Percival, C.; Bannan, T. J.; Priestley, M.; Hallquist, Å. M.; Kleist, E.; Kiendler-Scharr, A.; Hallquist, M.; Berndt, T.; McFiggans, G.; Wildt, J.; Mentel, T. F.; Ehn, M. Multi-Generation OH Oxidation as a Source for Highly Oxygenated Organic Molecules from Aromatics. Atmospheric Chemistry and Physics 2020, 20 (1), 515–537. https://doi.org/10.5194/acp-20-515-2020.

Yao, L.; Garmash, O.; Bianchi, F.; Zheng, J.; Yan, C.; Kontkanen, J.; Junninen, H.; Mazon, S. B.; Ehn, M.; Paasonen, P.; Sipilä, M.; Wang, M.; Wang, X.; Xiao, S.; Chen, H.; Lu, Y.; Zhang, B.; Wang, D.; Fu, Q.; Geng, F.; Li, L.; Wang, H.; Qiao, L.; Yang, X.; Chen, J.; Kerminen, V.-M.; Petäjä, T.; Worsnop, D. R.; Kulmala, M.; Wang, L. Atmospheric New Particle Formation from Sulfuric Acid and Amines in a Chinese Megacity. Science 2018, 361 (6399), 278–281. https://doi.org/10.1126/science.aao4839.

Bianchi, F.; Garmash, O.; He, X.; Yan, C.; Iyer, S.; Rosendahl, I.; Xu, Z.; Rissanen, M. P.; Riva, M.; Taipale, R.; Sarnela, N.; Petäjä, T.; Worsnop, D. R.; Kulmala, M.; Ehn, M.; Junninen, H. The Role of Highly Oxygenated Molecules (HOMs) in Determining the Composition of Ambient Ions in the Boreal Forest. Atmospheric Chemistry and Physics 2017, 17 (22), 13819–13831. https://doi.org/10.5194/acp-17-13819-2017.