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News 8.11.2021

Sources of black carbon at residential and traffic environments obtained by two source apportionment methods

Finnish Meteorological Institute was leading a study that mapped the origins of black carbon particles in Helsinki, Finland. Black carbon was measured with two different measurement instruments and the data was analyzed using two different source apportionment methods.
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This study investigated the sources of black carbon (BC) at two urban environments in Helsinki, Finland, residential area and street canyon, by using positive matrix factorization (PMF) and aethalometer model. PMF was applied to the organic and refractory black carbon (rBC) mass spectra collected with a soot particle aerosol mass spectrometer (SP-AMS), whereas the source apportionment by the Aethalometer model was calculated with two pairs of absorption Ångström values.

Based on the PMF analysis, the largest fraction of BC originated from biomass burning at the residential site (38 %) and from the vehicular emissions in the street canyon (57 %). Also, the mass size distribution of BC varied between the sites as BC from traffic was found at the particle size of ∼ 100–150 nm whereas BC from biomass combustion was detected at ∼ 300 nm. However, at both sites, a significant fraction of BC was associated with urban background or long-range-transported BC.

Comparison between the results from the PMF analysis and Aethalometer model showed that several PMF factors can be attributed to wood combustion and fossil fuel fraction of BC provided by the Aethalometer model. Furthermore, the Aethalometer model showed less variation between the sources within a day, suggesting that it was less responsive to the fast changes in the BC sources, or it could not differentiate between as many sources as PMF due to the similar optical properties of the BC sources.

More information:

Senior Researcher Sanna Saarikoski, Finnish Meteorological Institute, tel. +358 50 5906091,

Saarikoski, S., Niemi, J. V., Aurela, M., Pirjola, L., Kousa, A., Rönkkö, T., and Timonen, H.: Sources of black carbon at residential and traffic environments obtained by two source apportionment methods, Atmos. Chem. Phys., 21, 14851–14869,, 2021.

Scientific article available here

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