Modelling Black Carbon concentrations in two busy street canyons in Brussels using CANSBC

This paper focused on modelling Black Carbon (BC) concentrations in two busy street canyons, the Crown and Belliard Street in Brussels. The used original Operational Street Pollution Model was adapted to BC by eliminating the chemical module and is noted here as CANSBC. Model validations were performed using temporal BC data from the fixed measurement network in Brussels. Subsequently, BC emissions were adjusted so that simulated BC concentrations equalled the observed ones, averaged over the whole period of simulation. Direct validations were performed for the Crown Street, while BC model calculations for the Belliard Street were validated indirectly using the linear relationship between BC and NO_x. Concerning the Crown Street, simulated and observed half-hourly BC concentrations correlated well (r = 0.74) for the period from July 1st, 2011 till June 30th, 2013. In particular, CANSBC performed very well to simulate the monthly and diurnal evolutions of averaged BC concentrations, as well as the difference between weekdays and weekends. This means that the model correctly handled the meteorological conditions as well as the variation in traffic emissions. Considering dispersion, it should however be noted that BC concentrations are better simulated under stable than under unstable conditions. E ven if the correlation on half-hourly NO_x concentrations was slightly lower (r = 0.60) than the one of BC, indirect validations of CANSBC for the Belliard Street yielded comparable results and conclusions as described above for the Crown Street. Based on our results, it can be stated that CANSBC is suitable to accurately simulate BC concentrations in the street canyons of Brussels, under the following conditions: (i) accurate vehicle counting data is available to correctly estimate traffic emissions, and (ii) vehicle speeds are measured in order to improve emission estimates and to take into account the impact of the turbulence generated by moving vehicles on the local dispersion of BC.

Brasseur, O., P. Declerck, B. Heene, & P. Vanderstraeten (2015) Modelling Black Carbon concentrations in twobusy street canyons in Brussels using CANSBC, ATMOSPHERIC ENVIRONMENT 101:72-81.