Increasing the spatial resolution of air quality assessments in urban areas: A comparison of biomagnetic monitoring and urban scale modelling

Increasing the spatial resolution of air quality assessments in urban environments is designated as a priority area within current research. Biomagnetic monitoring and air quality modelling are both methodologies able to provide information about the spatial variation of particulate pollutant levels within urban environments. This study evaluates both methods by comparing results of a biomagnetic monitoring campaign at 110 locations throughout Antwerp, Belgium, with modelled pollutant concentrations of PM10 and NO2. Due to the relation of biomagnetic monitoring with railway traffic, analyses were conducted for both all locations (n = 110) and railway traffic excluded locations (n = 67). While the general spatial variation, land use comparison and the relation with traffic intensity were comparable between the two applied methodologies, an overall bad agreement is obtained when the methodologies are correlated to each other. While no correlation was found between SIRM and PM10 results (p = 0.75 for n = 110 and p = 0.68 for n = 67), a significant but low (r ≤ 0.33) correlation was found between SIRM and NO2 (p < 0.01 for n = 110 and p = 0.04 for n = 67). While biomagnetic monitoring and air quality modelling are both able to provide high spatial resolution information about urban pollutant levels, we need to take into account some considerations. While uncertainty in the biomagnetic monitoring approach might arise from the processes that determine leaf particulate deposition and the incorporation of multiple emission sources with diverging magnetic composition, air quality modelling remains an approximation of reality which implies its dependency on accurate emission factors, implication of atmospheric processes and representation of the urban morphology. Therefore, continuous evaluation of model performance against measured data is essential to produce reliable model results. Nevertheless, this study demonstrates that in addition to telemetric monitoring networks, the combination of both air quality modelling and biomagnetic monitoring is a valuable approach to provide insights into the variation of atmospheric pollutants in heterogeneous urban environments.