PM10 source apportionment applying PMF and chemical tracer analysis to ship-borne measurements in the Western Mediterranean

A PM10 sampling campaign was carried out on board the cruise ship Costa Concordia during 19 three weeks in summer 2011. The ship route was Civitavecchia-Savona-Barcelona-Palma de 20 Mallorca-Malta (Valletta)-Palermo-Civitavecchia. The PM10 composition was measured and 21 utilized to identify and characterize the main PM10 sources along the ship route through 22 receptor modelling, making use of the Positive Matrix Factorization (PMF) algorithm. A 23 particular attention was given to the emissions related to heavy fuel oil combustion by ships, 24 which is known to be also an important source of secondary sulphate aerosol. Five aerosol 25 sources were resolved by the PMF analysis. The primary contribution of ship emissions to 26 PM10 turned out to be (12 ± 4)%, while secondary ammonium sulphate contributed by (35 ± 27 5)%. Approximately, 60% of the total sulphate was identified as secondary aerosol while 28 about 20% was attributed to heavy oil combustion in ship engines. The measured 29 concentrations of methanesulphonic acid (MSA) indicated a relevant contribution to the 30 observed sulphate loading by biogenic sulphate, formed by the atmospheric oxidation of 31 dimethyl sulphide (DMS) emitted by marine phytoplankton