a b s t r a c tParticle composition data for PM 10 samples collected at an urban background location in Elche in southeastern Spain from December 2004 to November 2005 were analysed to provide source identification and apportionment. A total of 120 samples were collected and analysed by Particle Induced X-ray Emission (PIXE) and ion chromatography. Positive matrix factorization (PMF) was used to estimate sources profiles and their mass contributions. The PMF modelling identified six sources: PM 10 mass was apportioned to secondary nitrate (26%), secondary sulphate (22%), local soil dust (21%), traffic (13%), seasalt (11%) and African dust (7%). It is worth noting that PMF was able to identify a Saharan dust source even in the presence of a weighty local dust source, and to quantitatively estimate the contributions of these two sources. The African dust contribution varies, depending on the intrusion days, within a range of 5-40% of the total PM 10 concentration. Without the contribution of Saharan dust, 50% of the total exceedances of the PM 10 50 mg m À3 EC limit during the studied period would not have taken place.
PM2.5 and PM10 samples were collected in the urban atmosphere of Elche (southeastern Spain) between December 2004 and November 2005. The samples were analyzed for mass and water-soluble inorganic ions (Na + , NH þ 4 , K + , Ca 2+ , Mg 2+ , Cl − , NO À 3 and SO 2À 4 ) with the aim of investigating the influence of the climatic and geographic features of a coastal semiarid area on the contribution of these species to PM levels. Secondary inorganic ions (SO 2À 4 , NO À 3 , NH þ 4 ) were the major components in the fine fraction (PM2.5), accounting for 40% of the total mass. The relationship between non-marine SO 2À 4 and NH þ 4 indicated that fine sulfate particles were completely neutralized by ammonium. In the coarse fraction (PM10-2.5), nitrate (as NaNO 3 and Ca(NO 3 ) 2 ), together with crustal (CaCO 3 ) and marine species (NaCl) accounted for almost 50% of the total mass. Fine sulfate and coarse nitrate showed summer maximums. In contrast, the concentrations of fine NO À 3 were lowest in the warm period. Ammonium presented both winter and summer maximums. The levels of marine ions, except for coarse Cl − , were highest in summer when the dominant wind flow is from the sea. No significant seasonal variations were observed for coarse Ca 2+ and SO 2À 4 . The concentrations of all inorganic ions increased during Saharan dust events, in particular, fine NH þ 4 and SO 2À 4 and coarse NO À 3 . Coarse calcium was proved not to be a good tracer for this type of episode in our region since the average levels of this cation are elevated and the relative increase in its concentrations during African events was not as high as expected.
Particle-bound PAHs were measured at three sites in southeastern Spain (an urban background location, a suburban-industrial site in the vicinity of two cement plants and a rural area) in order to investigate the influence of the type of location on PAH concentrations. A clear influence of cement production on particulate PAH levels could not be established since for the urban background and suburban-industrial sites the average concentrations of total PAHs in the PM2.5 fraction were very similar (1.085 and 1.151 ng m(-3), respectively), with benzo[b+k]fluoranthene and chrysene as the predominant compounds. Diagnostic ratios, used to identify PAH emission sources, pointed to traffic as the main source of particulate PAH at both locations. As expected, PAH levels at the rural site were significantly lower (0.408 ng m(-3) in the PM10 fraction) due to increasing distance from the emission sources. PAH seasonal variations at the urban background and suburban-industrial sites were the same as reported in many previous studies. Average winter to summer ratios for total PAHs were 4.4 and 4.9 for the urban background and industrial sites, in that order. This seasonal cycle could be partially explained by the higher temperature and solar radiation during summer enhancing PAH evaporation from the particulate phase and PAH photochemical degradation, respectively. The study of PAH distribution between the fine and coarse fraction at the urban site revealed that on average around 80% of total PAHs were associated with fine particles.
Continuous measurements of particle mass size distributions were carried out in summer 2004 at an urban location in the western Mediterranean using an optical particle counter. In this work we propose a simple methodology to identify PM episodes and determine their influence on mass size distributions. During the study period three types of event produced a significant increase in TSP daily levels: Saharan dust intrusions, firework displays and strong winds, modifying size distributions in different ways. As well, a traffic-related mass size spectrum was obtained showing road dust particles injected into the atmosphere by vehicle-induced resuspension having mainly aerodynamic diameters between 5 and 15 microm. This was confirmed by principal component and conditional probability function analyses.
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