A comprehensive source apportionment of submicron aerosols in Metz, France, by PMF2
Résumé
The source apportionment of atmospheric particulate matter (PM) in European urban areas has become a great scientific concern as well as a significant part of stakeholder initiatives in the last decade. This is notably related to growing evidences of PM sanitary impact, and to increasing pressures on the compliance with European legislation. However, the complex and constant interactions between emission sources, chemical composition and meteorological conditions make our understanding of the PM origins and (trans-)formation processes still challenging. In this context, Aerosol Mass Spectrometers have greatly improved our knowledge of particulate pollution. In particular, the Aerosol Chemical Speciation Monitor (ACSM, Ng et al., 2011) has been specifically designed for long-term monitoring of the major chemical composition of non-refractory submicron aerosols. Combined with multi-wavelength Aethalometer (Drinovek et al., 2014), it has been demonstrated to be an efficient tool to characterize persistent pollution episodes (Petit et al., 2014a). Taking advantage of the robustness of these instruments, and in a national impetus of settling efficient mitigation policies, an ACSM and a multi-wavelength Aethalometer have been implemented within the Lorraine air quality monitoring network (Air Lorraine). Located in Metz, a major city in the East of France, measurements are representative of urban background conditions. Similarly to Petit et al. (2014b), where two subsequent Positive Matrix Factorization (PMF, Paatero, 1994) analyses led to a refined assessment of the wintertime PM pollution sources in Paris, France, a PMF² methodology has been used on a 2-month dataset, containing: previously apportioned Organic Aerosol (OA) factors, NO3-, SO42-, NH4+, Cl-, apportioned Black Carbon (BCwb and BCff), and some inorganic gases such as NO2, NO and SO2. The first PMF analysis was applied to the organic mass spectrum, constraining Hydrocarbon-like Organic Aerosol (HOA) reference profile. It led to a 3-factor solution with two unconstrained factors, which seem to be linked with biomass burning and/or secondary organic aerosols.