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Physical and chemical characterization of urban winter-time aerosols by mobile measurements in Helsinki, Finland

Physical and chemical characterization of urban winter-time aerosols by mobile measurements in Helsinki, Finland

Aerosol properties and sources in urban environments were investigated in the Helsinki metropolitan area, Finland, in winter 2012 by a mobile laboratory van. Physico-chemical properties of particles varied strongly in time and space, depending on the main sources of aerosols.

Four major types of aerosol were identified: 1) clean background aerosol with small particle number and lung deposited surface area concentrations due to marine air flows from the Atlantic Ocean, 2) long-range transported (LRT) pollution aerosol due to air flows from eastern Europe, 3) fresh smoke plumes from residential wood combustion in suburban small houses, and 4) fresh emissions from traffic while driving on busy streets in the city centre and on the highways during morning rush hours. In general, primary aerosol components (black carbon, hydrocarbon-like organic aerosol and biomass burning organic aerosol) dominated the local traffic and wood burning emissions whereas secondary components (oxygenated organic aerosol, nitrate, ammonium, and sulfate) dominated the PM1 chemical composition during the LRT episode. The major individual particle types observed with electron microscopy analysis (TEM/EDX) were mainly related to residential wood combustion (K/S/C-rich, soot, other C-rich particles), traffic (soot, Si/Al-rich, Fe-rich), heavy fuel oil combustion in heat plants or ships (S with V-Ni-Fe), LRT pollutants (S/C-rich secondary particles) and sea salt (Na/Cl-rich). Tar balls from wood combustion were also observed, especially (~5%) during the LRT pollution episode. A comprehensive view of aerosol properties and sources in urban air is important for air quality assessment, in characterizing human exposure, and for climate models. For the use of epidemiological studies and exposure estimation, it is important to know lung deposited surface area concentrations and size distributions at different populated areas.

More information:

 

Sanna Saarikoski, tel. +358 50 590 6091

sanna.saarikoski@fmi.fi

 

Liisa Pirjola, tel. +358 40 731 8045

liisa.pirjola@metropolia.fi

 

Pirjola, L., Niemi, J. V., Saarikoski, S., Aurela, M., Enroth, J., Carbone, S., Saarnio, K., Kuuluvainen, H., Kousa, A., Rönkkö, T., Hillamo, R. 2017; Physical and chemical characterization of urban winter-time aerosols by mobile measurements in Helsinki, Finland. Atmos. Environ. 158:60–75.

http://www.sciencedirect.com/science/article/pii/S1352231017301607

 


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