The doctoral dissertation in the field of Environmental Sciences will be examined at the Faculty of Science, Forestry and Technology, Kuopio campus.
What is the topic of your doctoral research?
My doctoral research focuses on the tiny aerosol particles released when biomass, wood, peat, grass etc., are burned, whether in small household stoves or during wildfires. These particles, known as black and brown carbon, are far smaller than a strand of hair, yet they have enormous effects on the air we breathe and the climate we live in. They harm human health, and depending on their structure and chemistry, they can either have warming or cooling effect on Earth's atmosphere.
This research is important because boreal forest and peatland fires are expected to become more common as the climate changes, which will increase aerosol emissions.
In Northern Europe, burning wood at home is a main source of fine particles and black carbon in ambient air. Understanding how these particles form, change, and interact with sunlight is important for making climate models better, reducing uncertainty in climate predictions, and helping to create strategies that protect health and the environment.
What are the key findings or observations of your doctoral research?
The main findings show that the amount and type of carbon aerosols released from burning biomass depend on the kind of fuel, how it burns, and how long the particles spend in the atmosphere. Smouldering fires release more organic aerosols with strong brown carbon absorption, while flaming fires produce more black carbon particles. As these particles age in the air, their properties change: they become more oxidized, their size and shape shift, and they often absorb more light because of coatings that form around them. The way brown carbon absorbs light also changes in complex ways depending on the source.
Another important observation is that burning peat and boreal biomass, which is common in northern Europe, releases a lot of organic aerosols with unique optical properties that climate models do not yet capture well. Also, modern small-scale woodstoves for homes, especially those with electrostatic precipitators, can greatly lower the amount and number of particles released, thus reducing the health and climate impacts.
For scientists, the results help make climate models more accurate by reducing uncertainty about how aerosols affect sunlight and by improving how brown carbon is represented. For public, the findings show that residential heating choices and more frequent wildfires have a direct impact on air quality, climate, and health. We also showed electrostatic precipitators can help reduce harmful aerosol particles from household woodstove emissions.
How can the results of your doctoral research be utilised in practice?
Firstly, my doctoral work provide improved emission factors and detailed aerosol property data that can be directly used in air quality and climate models, helping climate modellers make more accurate assessments of pollution sources and climate impacts.
Secondly, the findings support the development and optimization of cleaner residential wood combustion technologies, such as electrostatic precipitators (ESP), and promote better combustion practices to reduce harmful emissions.
In addition, the work highlights the importance of accounting for brown carbon aerosols and atmospheric aging in regulatory frameworks to improve emission inventories and mitigation strategies. For the public, the results underline how everyday heating choices influence air quality and health, encouraging more sustainable practices.
Overall, this research contributes to more effective strategies for reducing particulate pollution, protecting human health, and mitigating climate change.
What are the key research methods and materials used in your doctoral research?
The doctoral research was carried out through controlled experiments in ILMARI laboratory. Different vegetations, including beech wood, South African savanna, Finnish boreal forest surface, and peatlands from Finland, Russia, and Svalbard (Norway) were combusted under various realistic conditions. Emitted particle number size distributions were measured using particle mobility sizers (SMPS); while particle mass, effective density, and morphology were analyzed using instruments such as an aerosol particle mass analyzer (APM) and electron microscopy.
The chemical composition of particles was determined using methods such as aerosol mass spectrometry and thermal-optical carbon analysis. Optical properties, including light absorption by black and brown carbon, were measured using aethalometers and UV-vis spectrophotometers. Emissions were subjected to photochemical and dark aging in an environmental chamber and oxidation flow reactor (PEAR) to simulate realistic atmospheric chemical transformation.
The doctoral dissertation of Arya Mukherjee, MSc, entitled Characterization of black and brown carbon aerosols from closed and open biomass burning will be examined at the Faculty of Science, Forestry and Technology, Kuopio campus, on 22 May 2026. The opponent will be Coordinating Researcher Célia Alves (University of Aveiro, Aveiro, Portugal), and the custos will be Professor Olli Sippula (University of Eastern Finland). Language of the public defence is English.
Further information:
Doctoral Researcher Arya Mukherjee, [email protected]