A study has been carried out in order to know the concentration levels of the different elements present in the fine atmospheric particles (PM10) and to speciate the iron compounds The trace metal concentrations (Fe, Ni, Cu, Zn and Pb) were determined, as well as the presence of other polluting agents. The samples were collected during dry and rainy of 2005 and 2006, using a high volume air sampler located 70 m above sea level, in the roof of Colina building, University of Panama. ICP Optical Emission Spectrometry (ICP-OES) and Mössbauer Spectroscopy were used. The concentrations of PM10 in Panama City were generally low, staying below the permissible daily limit of 50 ?g m-3, but above the recommended internationally value of 40 ?g m-3. On the other hand, during dry season, the values of PM10 are higher, whereas the lowest values, below the limit, were detected in the rainy months of October and November. The particulate matter has higher concentrations of Na, K, Mg, Ca and Fe, exhibiting a seasonal pattern of larger concentrations during dry season; meanwhile the other found elements, with much smaller concentrations, did not show a defined seasonal pattern. With the aid of Mössbauer spectroscopy iron oxides (?-Fe2O3) of fine and ultra-fine grain size (nanometric), ferric oxyhydroxides (?-FeOOH, ?-FeOOH) and Fe3+ and Fe2+ silicates were identified. Disregarding the time of the year, the main sources of particulate matter are the eroded soils, cement and other materials from the construction industries in the city, and vehicle emissions.
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