One year online chemical speciation of submicron particulate matter (PM1) sampled at a French industrial and coastal site
Résumé
The harbor of Dunkirk (Northern France) is surrounded by different industrial plants (metallurgy, petrochemistry,
food processing, power plant, etc.), which emit gaseous and particulate pollutants such as Volatile Organic Compounds (VOCs), oxides of nitrogen (NOx) and sulfur (SO2), and submicron particles (PM1). These emissions are
poorly characterized and their impact on neighboring urban areas has yet to be assessed. Studies are particularly
needed in this type of complex environments to get a better understanding of PM1sources, especially from the
industrial sector, their temporal variability, and their transformation.
Several instruments, capable of real-time measurements (temporal resolution ≤ 30 min), were deployed at a site
located downwind from the industrial area of Dunkirk for a one-year duration (July 2013-September 2014). An
Aerosol Chemical Speciation Monitor (ACSM) and an Aethalometer monitored the main chemical species in the
non-refractory submicron particles and black carbon, respectively. Concomitant measurements of trace gases and
wind speed and direction were also performed. This dataset was analyzed considering four wind sectors, characteristics of marine, industrial, industrial-urban, and urban influences, and the different seasons. We will present a
descriptive analysis of PM1, showing strong variations of ambient concentrations, as well as evidences of SO2 to
SO4 gas-particle conversion when industrial plumes reached the monitoring site. The organic fraction measured by
ACSM (37% of the total mass on average) was analyzed using a source-receptor model based on Positive Matrix
Factorization (PMF) to identify chemical signatures of main emission sources and to quantify the contribution
of each source to the PM1 budget given the wind sector. Four main factors were identified: hydrocarbon organic
aerosol (HOA), oxygenated organic aerosol (OOA), biomass burning organic aerosol (BBOA) and cooking-like
organic aerosol (COA). Overall, the total PM1 mass loading was dominated by secondary inorganic species and
OOA. The seasonal variations of different identified factors will be discussed as well as the influence of ship
emissions.