Articles | Volume 17, issue 13
Research article
07 Jul 2017
Research article |  | 07 Jul 2017

Organic aerosol source apportionment by offline-AMS over a full year in Marseille

Carlo Bozzetti, Imad El Haddad, Dalia Salameh, Kaspar Rudolf Daellenbach, Paola Fermo, Raquel Gonzalez, María Cruz Minguillón, Yoshiteru Iinuma, Laurent Poulain, Miriam Elser, Emanuel Müller, Jay Gates Slowik, Jean-Luc Jaffrezo, Urs Baltensperger, Nicolas Marchand, and André Stephan Henry Prévôt

Abstract. We investigated the seasonal trends of OA sources affecting the air quality of Marseille (France), which is the largest harbor of the Mediterranean Sea. This was achieved by measurements of nebulized filter extracts using an aerosol mass spectrometer (offline-AMS). In total 216 PM2. 5 (particulate matter with an aerodynamic diameter  <  2.5 µm) filter samples were collected over 1 year from August 2011 to July 2012. These filters were used to create 54 composite samples which were analyzed by offline-AMS. The same samples were also analyzed for major water-soluble ions, metals, elemental and organic carbon (EC ∕ OC), and organic markers, including n-alkanes, hopanes, polycyclic aromatic hydrocarbons (PAHs), lignin and cellulose pyrolysis products, and nitrocatechols. The application of positive matrix factorization (PMF) to the water-soluble AMS spectra enabled the extraction of five factors, related to hydrocarbon-like OA (HOA), cooking OA (COA), biomass burning OA (BBOA), oxygenated OA (OOA), and an industry-related OA (INDOA). Seasonal trends and relative contributions of OA sources were compared with the source apportionment of OA spectra collected from the AMS field deployment at the same station but in different years and for shorter monitoring periods (February 2011 and July 2008). Online- and offline-AMS source apportionment revealed comparable seasonal contribution of the different OA sources. Results revealed that BBOA was the dominant source during winter, representing on average 48 % of the OA, while during summer the main OA component was OOA (63 % of OA mass on average). HOA related to traffic emissions contributed on a yearly average 17 % to the OA mass, while COA was a minor source contributing 4 %. The contribution of INDOA was enhanced during winter (17 % during winter and 11 % during summer), consistent with an increased contribution from light alkanes, light PAHs (fluoranthene, pyrene, phenanthrene), and selenium, which is commonly considered as a unique coal combustion and coke production marker. Online- and offline-AMS source apportionments revealed evolving levoglucosan : BBOA ratios, which were higher during late autumn and March. A similar seasonality was observed in the ratios of cellulose combustion markers to lignin combustion markers, highlighting the contribution from cellulose-rich biomass combustion, possibly related to agricultural activities.

Short summary
We present the first long-term organic aerosol source apportionment in an environment influenced by anthropogenic emissions including biomass burning and industrial processes and an active photochemistry. Online and offline aerosol mass spectrometry were used to characterize these emissions and their transformation. Measurements of organic markers provided insights into the origin of biomass smoke in this area, with different seasonal contributions from domestic heating and agricultural burning.
Final-revised paper