Combined Eulerian-Lagrangian Hybrid Modelling System for PM2.5 and Elemental Carbon Source Apportionment at the Urban Scale in Milan

Giovanni Lonati,Guido Pirovano,Alessandra Balzarini,Nicola Pepe,Giuseppe Maurizio Riva,Anna Toppetti

doi:10.3390/atmos11101078

Giovanni Lonati, Guido Pirovano + Show 4 more

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Air quality modeling at the very local scale within an urban area is performed through a hybrid modeling system (HMS) that combines the CAMx Eulerian model the with AUSTAL2000 Lagrangian model. The enhancements obtained by means of the HMS in the reconstruction of the spatial distribution of fine particles (PM2.5) and elemental carbon (EC) concentration are presented for the case-study of Milan city center in Northern Italy. Modeling results are reported for three receptors (a green area, a residential and shopping area, and a congested crossroad on the inner ring road of the city center) selected in order to represent urban sites characterized by both different features in terms of the surrounding built environment and by different exposure to local emission sources. The peculiarity of the three receptors is further highlighted by source apportionment analysis, developed not only with respect to the kind of emission sources but also to the geographical location of the sources within the whole Northern Italy computational domain. Results show that the outcome of the Eulerian model at the local scale is only representative of a background level, similar to the Lagrangian model’s outcome for the green area receptor, but fails to reproduce concentration gradients and hot-spots, driven by local sources’ emissions.

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Air pollution in urban areas is a significant public health issue because of chronic diseases, principally of respiratory and cardiovascular nature [1], and because of premature deaths resulting from population exposure to atmospheric pollutants [2,3,4]
From April corresponding estimates provided by CAMx for the3three receptors of the urban area 3in order to point to October PM2.5 levels are always below 0.9 μg/m, but they are around 0.5 μg/m from June to out the accuracy increase that can arise from coupling the local-scale Lagrangian approach with the August
Results for ambient PM2.5 and elemental carbon (EC) levels estimated by AUSTAL2000 have been compared to the corresponding estimates provided by CAMx for the three receptors of the urban area in order to point out the accuracy increase that can arise from coupling the local-scale

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Air pollution in urban areas is a significant public health issue because of chronic diseases, principally of respiratory and cardiovascular nature [1], and because of premature deaths resulting from population exposure to atmospheric pollutants [2,3,4]. In 2015, air pollution-related diseases were estimated to be responsible for about 6.4 million premature deaths worldwide, with 4.2 million due to ambient air pollution. Air quality monitoring networks provide data in order to check the compliance with air quality limits. Monitoring sites are usually limited in number and, even though located at sites supposedly representative of different urban microenvironments, their data may not properly assess the actual air quality over the whole urban area [6]

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