Wood burning releases high amounts of secondary organic aerosols - current emission estimates too low

Aerosol emissions from logwood combustion increase significantly when the emission ages in ambient air. A significant increase occurs already within three hours of aging, according to a new study from the University of Eastern Finland. The emission increase was caused by the formation of secondary organic aerosols (SOA) in which gaseous organic compounds, released during the combustion, oxidise and condense on aerosol particles. This observation is very important, because current emission inventories do not take SOA emissions into consideration at all. 

The analyses were carried out in the ILMARI research laboratory at the University of Eastern Finland in collaboration with the Finnish Meteorological Institute, and they constituted part of the activities of the European HICE Helmholtz Virtual Institute network. The laboratory experiments showed that plenty of organic gaseous compounds get released especially during the ignition and fuel addition phases in batch combustion, and these compounds form secondary aerosols in the atmosphere. Furthermore, the ignition method greatly impacts the emission level: a slower ignition significantly increased the emissions of organic compounds.  

The researchers also found that there are differences in secondary emission levels during the day and night, and lower levels of SOA emissions formed during nighttime ageing. However, a substantial fraction of the particulate emissions were organonitrates during nighttime aging experiments. Organonitrates are an important but so far poorly characterized nitrogen-containing chemical group in the atmosphere. Out of the nitrate compounds present in the atmospheric particle phase, 34–44 per cent are organonitrates. A detailed analysis of the emission ageing process in a smog chamber revealed that the majority of primary organic aerosols (POA) released during wood combustion oxidized during their atmospheric ageing, unlike previously thought. 

The transformation process during aerosol ageing is important when considering the health and climatic effects of emissions, and these changes are currently being studied by an international multidisciplinary research network.  

For further information, please contact: 

Researcher Petri Tiitta, FINE, University of Eastern Finland, tel. +358 40 3553024, petri.tiitta@uef.fi 

Research Manager Olli Sippula, FINE, University of Eastern Finland, tel. +358 40 3553397, olli.sippula@uef.fi 

Original article: 

Transformation of logwood combustion emissions in a smog chamber: formation of secondary aerosol and changes in the primary organic aerosol upon daytime and nighttime aging. Tiitta, P., Leskinen, A., Hao, L., Yli-Pirilä, P., Kortelainen, M., Grigonyte, J., Tissari, J., Lamberg, H., Hartikainen, A., Kuuspalo, K., Kortelainen, A., Virtanen, A., Lehtinen, K. E. J., Komppula, M., Pieber, S., Prévôt, A. S. H., Onasch, T. B., Worsnop, D., Czech, H., Zimmermann, R., Jokiniemi, J., and Sippula, O., Atmos. Chem. Phys., 16, 13251-13269, doi: 10.5194/acp-16-13251-2016, 2016.

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The University of Eastern Finland is the most multidisciplinary university in Finland. Our high standard of interdisciplinary research and education respond to global challenges and build a sustainable future. Our research is ranked among the best in the world in several fields. We offer education in nearly 100 major subjects and we train experts for tomorrow’s changing labour market needs. The university comprises four faculties: the Philosophical Faculty, the Faculty of Science and Forestry, the Faculty of Health Sciences, and the Faculty of Social Sciences and Business Studies. Our campuses are located in Joensuu and Kuopio. The UEF is home to approximately 15 500 students and 2 700 members of staff.

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