Characterisation of Light-Absorbing Particles in the Brussels Sub-urban Atmosphere and Implications for the Emission Scheme of a Regional Chemical Transport Model

The Royal Meteorological Institute of Belgium (RMI) gathered ambient aerosol data in Brussels with a 7-wavelengths aethalometer and a 3 wavelengths integrating nephelometer. The amount of light-absorbing particles showed a clear daily and weekly cycle, with a sharp peak in the morning rush hour time and a broader peak in the evening. During weekends, the rush hour peak diminished. The spectral dependency of the absorption coefficient revealed peak contributions of traffic emissions to the amount of light-absorbing particles of up to 90%. Other sources (like wood burning from households) showed peak contributions of up to 35%. These percentages showed in addition a clear daily, weekly and seasonal cycle, with higher contributions of these other sources during night time, weekends and summer.