A one-year comprehensive chemical characterisation of fine aerosol (PM<sub>2.5</sub>) at urban, suburban and rural background sites in the region of Paris (France)

Abstract

Abstract. Studies describing the chemical composition of fine aerosol (PM2.5) in urban areas are often conducted for a few weeks only and at one sole site, giving thus a narrow view of their temporal and spatial characteristics. This paper presents a one-year (11 September 2009–10 September 2010) survey of the daily chemical composition of PM2.5 in the region of Paris, which is the second most populated "Larger Urban Zone" in Europe. Five sampling sites representative of suburban (SUB), urban (URB), northeast (NER), northwest (NWR) and south (SOR) rural backgrounds were implemented. The major chemical components of PM2.5 were determined including elemental carbon (EC), organic carbon (OC), and the major ions. OC was converted to organic matter (OM) using the chemical mass closure methodology, which leads to conversion factors of 1.95 for the SUB and URB sites, and 2.05 for the three rural ones. On average, gravimetrically determined PM2.5 annual mass concentrations are 15.2, 14.8, 12.6, 11.7 and 10.8 μg m−3 for SUB, URB, NER, NWR and SOR sites, respectively. The chemical composition of fine aerosol is very homogeneous at the five sites and is composed of OM (38–47%), nitrate (17–22%), non-sea-salt sulfate (13–16%), ammonium (10–12%), EC (4–10%), mineral dust (2–5%) and sea salt (3–4%). This chemical composition is in agreement with those reported in the literature for most European environments. On an annual scale, Paris (URB and SUB sites) exhibits its highest PM2.5 concentrations during late autumn, winter and early spring (higher than 15 μg m−3 on average, from December to April), intermediates during late spring and early autumn (between 10 and 15 μg m−3 during May, June, September, October, and November) and the lowest during summer (below 10 μg m−3 during July and August). PM levels are mostly homogeneous on a regional scale, during the whole project (e.g. for URB plotted against NER sites: slope = 1.06, r2=0.84, n=330), suggesting the importance of mid- or long-range transport, and regional instead of local scale phenomena. During this one-year project, two thirds of the days exceeding the PM2.5 2015 EU annual limit value of 25 μg m−3 were due to continental import from countries located northeast, east of France. This result questions the efficiency of local, regional and even national abatement strategies during pollution episodes, pointing to the need for a wider collaborative work with the neighbouring countries on these topics. Nevertheless, emissions of local anthropogenic sources lead to higher levels at the URB and SUB sites compared to the others (e.g. 26% higher on average at the URB than at the NWR site for PM2.5, during the whole campaign), which can even be emphasised by specific meteorological conditions such as low boundary layer heights. OM and secondary inorganic species (nitrate, non-sea-salt sulfate and ammonium, noted SIA) are mainly imported by mid- or long-range transport (e.g. for NWR plotted against URB sites: slope = 0.79, r2=0.72, n=335 for OM, and slope = 0.91, r2=0.89, n=335 for SIA) whereas EC is primarily locally emitted (e.g. for SOR plotted against URB sites: slope = 0.27; r2=0.03; n=335). This database will serve as a basis for investigating carbonaceous aerosols, metals as well as the main sources and geographical origins of PM in the region of Paris.

Chemical characterization and source identification of PM<sub>2.5</sub> at multiple sites in the Beijing–Tianjin–Hebei region, China

“…Although the literature suggests that a higher OC to OM conversion factor of 2.1 is suitable for rural sites (Bressi et al, 2013;Turpin and Lim, 2001), we still used a uniform value of 1.6 for the sake of spatial comparisons. Therefore, Christoforou et al, 2000).…”

“…The PM mass and its chemical compositions are governed by chemical processes, the evolution of emission sources, and meteorological conditions (Bressi et al, 2013;, which usually exhibit seasonality. The seasonal patterns of PM 2.5 at the urban sites were mainly driven by OM, SNA, and mineral dust, which were the major components of PM 2.5 during each season.…”

Optical, physical and chemical properties of aerosols transported to a coastal site in the western Mediterranean: a focus on primary marine aerosols

“…More details on this instrumentation and its comparability with other real-time aerosol analysers can be found in Zorn et al (2008); Sciare et al (2011);Healy et al (2013); Crippa et al (2013); Bressi et al (2013). Basic and acidic annular denuders (3-channel, URG Corp., USA) were mounted upstream of the PILS instrument and downstream of a PM10 inlet having a 50 % cut-off diameter of 10 µm at 16.67 LPM.…”

“…PMA concentration was calculated using these data and the following formula (Brewer, 1975): (Cl), with a time resolution of 30 min. The chemical composition of non-refractory submicron aerosol has been continuously monitored using a Quadrupole Aerosol Chemical Speciation Monitor (Aerodyne Research Inc.), which has been described in detail by Ng et al (2011).…”

Intermittent turbulence contributes to vertical diffusion of PM<sub>2.5</sub> in the North China Plain

“…Meanwhile, it is reported that climate change and synoptic circulation (Miao et al, 2017;Ye et al, 2016;Zhang et al, 2012;Zheng et al, 2015a) are of great importance in the transport of pollutants as well. Air pollution is essentially a phenomenon of the atmospheric boundary layer (ABL) and is strongly 5 affected by the thermodynamic and dynamic structure of the ABL (Bressi et al, 2013;Gao et al, 2016;Tang et al, 2016).…”