Impact of harbour emissions on ambient PM10 and PM2.5 in Barcelona (Spain): Evidences of secondary aerosol formation within the urban area

Abstract

With the objective of estimating the impact of harbour activities on ambient PM10 and PM2.5 levels at the urban area of Barcelona, a one year long monitoring campaign was carried out in the context of the European APICE project (MED-FEDER-EC). This campaign was simultaneously conducted at the port and a central urban background site. A detailed PM10 and PM2.5 chemical speciation analysis was carried out with samples from both sites. Subsequently, a source apportionment analysis by means of the PMF receptor model was performed. Six common factors were identified, explaining local to regional emission sources (fuel oil combustion, industrial emissions, mineral-road dust resuspension, and road traffic emissions) and aerosol formation/transformation processes (secondary aerosols including ammonium sulphate and organic aerosols, and a mixed source accounting for aged sea spray and secondary nitrate). Around 50-55% PM10 and PM2.5 measured at the port was attributed to harbour activities: mineral matter from road dust and construction works of a new port area, vehicle traffic and fuel oil combustion. The estimated contribution of harbour emissions to the urban background reached 9-12% for PM10 and 11-15% for PM2.5 and is linked to primary emissions from fuel oil combustion but also to the formation of secondary aerosols. It becomes relevant to highlight the significantly higher contribution of secondary aerosols at the urban background when compared with the harbour site. Our hypothesis points to the fast formation of secondary ammonium sulphate within the city, after the reaction of SO2/H2SO4 transported by sea breezes with NH3, which is emitted in large amounts in Barcelona; and also to the enhanced formation of secondary organic aerosols within the city. This study broadens our knowledge on atmospheric phenomenology in urban Mediterranean cities and claims for effective abatement strategies focused on maritime practises, in agreement with the driving axis of the APICE project.

Keywords: Air quality; Fuel oil; Mediterranean; PM chemistry; PMF source apportionment; Shipping.