Overview of the French Operational Network for In Situ Observation of PM Chemical Composition and Sources in Urban Environments (CARA Program)

The CARA program has been running since 2008 by the French reference laboratory for air quality monitoring (LCSQA) and the regional monitoring networks, to gain better knowledge-at a national level-on particulate matter (PM) chemistry and its diverse origins in urban environments. It results in strong collaborations with international-level academic partners for state-of-the-art, straightforward, and robust results and methodologies within operational air quality stakeholders (and subsequently, decision makers). Here, we illustrate some of the main outputs obtained over the last decade, thanks to this program, regarding methodological aspects (both in terms of measurement techniques and data treatment procedures) as well as acquired knowledge on the predominant PM sources. Offline and online methods are used following well-suited quality assurance and quality control procedures, notably including inter-laboratory comparison exercises. Source apportionment studies are conducted using various receptor modeling approaches. Overall, the results presented herewith underline the major influences of residential wood burning (during the cold period) and road transport emissions (exhaust and non-exhaust ones, all throughout the year), as well as substantial contributions of mineral dust and primary biogenic particles (mostly during the warm period). Long-range transport phenomena, e.g., advection of secondary inorganic aerosols from the European continental sector and of Saharan dust into the French West Indies, are also discussed in this paper. Finally, we briefly address the use of stable isotope measurements (delta N-15) and of various organic molecular markers for a better understanding of the origins of ammonium and of the different organic aerosol fractions, respectively.

Automated summary

The CARA program, led by the French reference laboratory for air quality monitoring and regional monitoring networks since 2008, aims to enhance the national level understanding of particulate matter chemistry and origins in urban environments. The program has resulted in strong collaborations with international academic partners to produce state-of-the-art results and methodologies for air quality stakeholders and decision makers. Studies have highlighted the major influences of residential wood burning, road transport emissions, mineral dust, and primary biogenic particles on air quality, as well as long-range transport phenomena such as the advection of aerosols from European continental sectors and Saharan dust into French West Indies. Additionally, stable isotope measurements and organic molecular markers have been used for a better understanding of the origins of ammonium and organic aerosol fractions.