Characterization of PM10 and PM2.5 species from background air sampling at Giordan lighthouse global atmospheric watch station on Gozo

Abstract

From the start of December 2011 to the middle of September 2012 aerosols have been collected at the Giordan Lighthouse Global Atmospheric Watch background station on the island of Gozo, Malta in the Central Mediterranean in order to determine the aerosol composition and aerosol source apportionment in two size fractions. Using two low volume samplers and an array of analytical instruments for filter analysis at LSCE (Laboratoire des Sciences du Climat et de l'Environnement), Paris - namely transmissometry for black-brown carbon, microbalance weighing for particulate matter mass, carbon aerosol analysis for elemental-organic carbon, total organic carbon analysis for water soluble organic carbon, ion chromatography for anionscations-sugars; and X-Ray Fluorescence (XRF) for trace and heavy metals at the University of Malta XRF only managed to yield semi-quantitative data, however. Two size classes of aerosols were obtained - PM2_5 using quartz filters collecting particles smaller than 2.5 µm in aerodynamic diameter, as well as PM10 using PTFE filters collecting particles between 2 µm to 10 µm in aerodynamic diameter. Aerosol species have been isolated and source apportionment attempted using Principal Component Analysis and Pearson Correlation. The Central Mediterranean is heavily influenced by anthropogenic emissions from fossil fuel burning, both as a result of local emissions, which includes those from Malta, and the shipping channel in the immediate vicinity of the background station, as well as from transboundary pollutants from Central and Eastern Europe, North Africa, North America and Asia. Transboundary in this dissertation is defined as those aerosols originating from outside of the current study region and transported often great distances to the current sampling site. Aerosols from Mt. Etna were not found in the current study, with eight eruptions occurring during the study period and no peaks in sulfate or sulfur dioxide associated with these events being found. Sea salt aerosols contribute most to the coarse mode, accounting for 35 %, while sulfate aerosols are the biggest contributor in the fine mode, accounting for 39 %. Aerosol sources identified using principal component analysis based on the tracers analysed are anthropogenic, sea salt, mineral dust, marine, secondary organic, secondary inorganic, biogenic and biomass burning aerosols.