Analysis of airborne particulate matter with the combined use of particle induced X-ray emission, ion chromatography and scanning electron microscopy

Abstract The increasing atmospheric pollution is one of the most worrying problems in the world. Adverse health effects are associated to the air concentration of particulate matter with aerodynamic diameter less than 10 μm (PM10). The PM10 mass per m3 of air is one of the most important parameters used to estimate the air quality in Europe, since the European Directive 1999/30/EC became effective. This study presents the results of individual particle analyses performed on PM10 samples with different source contributions. The main objective is to characterize the chemical and mineralogical composition of the particulate matter in a coastal site near Venice, Italy. An extended PM10 sampling campaign was performed and concentrations of fifteen elements (Na, Mg, Al, Si, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn) and six inorganic ions (Cl−, NO3 −, SO4 2-, Na+, Mg2+, NH4 +) were determined using Particle Induced X-ray Emission (PIXE) and ion chromatography of watersoluble fractions, respectively. A varimax rotated factor analysis followed by a multi-linear regression analysis were performed on chemical data and five PM10 sources were identified and quantified: mineral dust, sea-salt, fossil fuel combustion, mixed anthropogenic pollution and secondary inorganic aerosol. A number of samples with very different source contributions to the daily levels of PM10 were also selected and an individual particle analysis by Scanning Electron Microscopy combined with Energy-Dispersive X-ray Spectrometry (SEM-EDS) was performed. Six different classes of particles were identified (mineral particles, chlorides, sulfates, elemental and organic carbon compounds, metals and biological particles) and an estimation of their abundance was made. Results show a relationship between source apportionment contributions and individual particle composition. This allows to extract further information on PM10 composition, source contributions, morphology, mineralogy and mixed state of particles and demonstrates the effectiveness of coupling the two approaches. Acknowledgement The authors gratefully acknowledge the support provided by Prof. P. Mittner (FISAMB-PD) and Laboratori Nazionali Legnaro – Istituto Nazionale di Fisica Nucleare (LNL-INFN) for PIXE and electron microscopy facilities, Dr. E. Ghedini, Prof. F. Pinna and Dr. M. Signoretto (Università Ca’ Foscari Venezia) for ion chromatography. The authors are also grateful to Comando Zona Fari e Segnalamenti Marittimi di Venezia for logistics.