PM2.5 samples were collected at two locations in Guadalajara: Centro and Miravalle, during 2007. The first site (Centro) is located downtown and characterized by high vehicular traffic. Miravalle is in the southern part of the city, and influenced by emissions from high industrial and vehicular activity. Samples were collected for 24 h and the annual median concentrations of PM2.5 observed were 44.1 and 52.8 microg m(-3) at Centro and Miravalle, respectively. The concentration of PM2.5 observed at the Miravalle site was significantly higher (p < 0.002). Ca, Fe, Zn, Mg and Pb were the most abundant elements found at both sites. Miravalle showed higher annual concentrations of Ca, Pb, Cu, Cr, Sr, Ni, Mo, Fe, Mn, and Sb with levels of 1013.9, 74.9, 28.2, 9.4, 6.3, 4.4, 1.0, 628.0, 23.7 and 4.6 ng m(-3), respectively. At Centro and Miravalle quarterly and annual concentrations of Pb did not exceed 290 ng m(-3) and all values are well below those specified by air quality standards. The Principal Component Analysis (PCA), Cluster Analysis and the enrichment factor (EF) based on the concentrations of each element indicated that the main source of particulates at Centro was of geological origin, while Miravalle receives emissions from natural and anthropogenic sources. Both contribute to the chemical composition of PM2.5 in Guadalajara.

In this study, the Enrichment Factors and elemental composition profiles of the PM2.5 were used to suggest the emission sources. The selected sites were Miravalle and Centro, and in both cases there were high values lead, Cadmium, Cobalt, Chromium, Cupper, Molybdenum, Nickel, Antimony, Selenium and Zinc for EF (>5), suggesting an anthropogenic origin. The remaining elements (Iron, Magnesium, Manganese, Strontium and Titanium) had Enrichment Factors <5, attributable to a geological origin, probably due to the suspension of particles from motor vehicles or wind. Comparing the elemental composition profiles of the two sites allowed establishing similarities with some reference profiles (SPECIATE database Version 4.2-EPA) from sources such as Paved Road Dust (PRD) and Industrial Soil (IS) and profiles of combustion sources such as Diesel Exhaust (DE). Through the estimation the Enrichment Factors and of the elemental composition profiles of two different sites in the city, it was possible to suggest not only the general type of emission source (geological or anthropogenic), but also more specific sources based on elemental composition of PM2.5.

The seasonal behavior of the mass of PM(2.5) and its elemental components and their contribution to the mass of the particles is described for two different sites in Guadalajara City. The average mass of the particles for the entire study period at the two sites, Centro and Miravalle (1.3 and 1.8 mg, respectively), showed significant differences (p<0.05), while differences (p<0.05) between seasons (rainy and dry season) only occurred at Miravalle. The total elemental contribution to the mass of the particles was 1.97% in Miravalle and 2.05% at Centro, with Iron and Titanium the largest contributors and most abundant elements for both sites. Likewise, the monthly contribution per element with respect to the monthly mass of all elements was estimated. The results revealed that the elements that present the biggest contribution to this mass were Iron, Titanium, Zinc and Magnesium. Iron was the largest contributor at both sites. At Miravalle, the contribution oscillated between 56 and 58% from January to June, while at Centro it oscillated between 55 and 40% for the same period of time.