Source apportionment of PM10 in the Western Mediterranean based on observations from a cruise ship

- PM samples obtained with hourly resolution on a cruise ship were analysed.
- Source apportionment by PMF with a moving receptor.
- Sulphate apportionment based on chemical tracers (Na, Ca, MSA).
- Correlation analysis using V and Ni as tracers of ship emissions.
- Ships have strong impact on sulphate concentrations in parts of the Mediterranean.

Two intensive PM10 sampling campaigns were performed in the summers of 2009 and 2010 on the ship Costa Pacifica during cruises in the Western Mediterranean. Samples, mainly collected on an hourly basis, were analysed with different techniques (Particle Induced X-Ray Emission, PIXE; Energy Dispersive - X Ray Fluorescence, ED-XRF; Ion Chromatography, IC; Thermo-optical analysis) to retrieve the PM10 composition and its time pattern. The data were used for obtaining information about the sources of aerosol, with a focus on ship emissions, through apportionment using chemical marker compounds, correlation analysis and Positive Matrix Factorization (PMF) receptor modelling. For the campaign in 2010, 66% of the aerosol sulphate was found to be anthropogenic, only minor contributions of dust and sea salt sulphate were observed while the biogenic contribution, estimated based on the measurements of MSA, was found to be more important (26%), but influenced by large uncertainties. V and Ni were found to be suitable tracers of ship emissions during the campaigns. Four sources of aerosol were resolved by the PMF analysis; the source having the largest impact on PM10, BC and sulphate was identified as a mixed source, comprising emissions from ships. The correlations between sulphate and V and Ni showed the influence of ship emissions on sulphate in marine air masses. For the leg Palma-Tunis crossing a main ship route, the correlations between aerosol sulphate and V and Ni were particularly strong (r2 = 0.9 for both elements).