Primary sources of PM<sub>2.5</sub> organic aerosol in an industrial Mediterranean city, Marseille

Abstract

Marseille, the most important port of the Mediterranean Sea, represents a challenging case study for source apportionment exercises, combining an active photochemistry and multiple emission sources, including fugitive emissions from industrial sources and shipping. This paper presents a Chemical Mass Balance (CMB) approach based on organic markers and metals to apportion the primary sources of organic aerosol in Marseille, with a special focus on industrial emissions. Overall, the CMB model accounts for the major primary anthropogenic sources including motor vehicles, biomass burning and the aggregate emissions from three industrial processes (heavy fuel oil combustion/shipping, coke production and steel manufacturing) as well as some primary biogenic emissions. This source apportionment exercise is well corroborated by ¹⁴C measurements. Primary OC estimated by the CMB accounts on average for 22% of total OC and is dominated by the vehicular emissions that contribute on average for 17% of OC mass concentration (vehicular PM contributes for 17% of PM_2.5). Even though industrial emissions contribute only 2.3% of the total OC (7% of PM_2.5), they are associated with ultrafine particles (<i>Dp</i><80 nm) and high concentrations of Polycyclic Aromatic Hydrocarbons (PAH) and heavy metals such as Pb, Ni and V. On one hand, given that industrial emissions governed key primary markers, their omission would lead to substantial uncertainties in the CMB analysis performed in areas heavily impacted by such sources, hindering accurate estimation of non-industrial primary sources and secondary sources. On the other hand, being associated with bursts of submicron particles and carcinogenic and mutagenic components such as PAH, these emissions are most likely related with acute ill-health outcomes and should be regulated despite their small contributions to OC. Another important result is the fact that 78% of OC mass cannot be attributed to the major primary sources and, thus, remains un-apportioned. We have consequently critically investigated the uncertainties underlying our CMB apportionments. While we have provided some evidence for photochemical decay of hopanes, this decay does not appear to significantly alter the CMB estimates of the total primary OC. Sampling artifacts and unaccounted primary sources also appear to marginally influence the amount of un-apportioned OC. Therefore, this significant amount of un-apportioned OC is mostly attributed to secondary organic carbon that appears to be the major component of OC during the whole period of study

Evaluation of a two-step thermal method for separating organic and elemental carbon for radiocarbon analysis

“…Most of the wood burned today was grown over the last 20-60 years, when 14 C levels were elevated in the atmosphere, following the nuclear bomb tests. Estimates based on tree growth models (e.g., Lewis et al, 2004;Mohn et al, 2008) give a range from 1.08 to 1.30 for biomass burning aerosols (Szidat et al, 2006(Szidat et al, , 2007Minguillón et al, 2011;El Haddad et al, 2011;Genberg et al, 2011;Gilardoni et al, 2011).…”

“…Radiocarbon ( 14 C) measurements allow to distinguish fossil from contemporary carbon sources of carbonaceous aerosol and have therefore become an important method of source apportionment (e.g., Currie, 2000;Szidat et al, 2006Szidat et al, , 2007Gelencser et al, 2007;Schichtel et al, 2008;Minguillon et al, 2011;El Haddad et al, 2011;Gilardoni et al, 2011;Glasius et al, 2011;Dusek et al, 2013). This method exploits the fact that the radioactive carbon isotope 14 C is not present in fossil fuels, whereas it is present at a typical contemporary level in carbonaceous material that derives from living biomass.…”

Sources and mixing state of summertime background aerosol in the north-western Mediterranean basin

“…This station is well positioned to investigate polluted air masses transported over the western Mediterranean basin from the highly industrialised regions of the Po Valley (Royer et al, 2010) and/or Marseille/Fos-Berre (El Haddad et al, 2011. The site was fully equipped for the measurement of aerosol chemical, physical and optical properties.…”

Particulate matter, air quality and climate: lessons learned and future needs

“…Chemical profiles are constructed for each known primary source, and the unapportioned mass is typically assigned to SOA (e.g. El Haddad et al, 2011;Stone et al, 2008). Some studies have attempted to also include markers related to SOA tracers .…”