oa Size-dependent elemental analysis of particulate matter pollutants in the UAE

We report on the study of industrial and natural aerosol pollutants in various UAE locations. Both indoor and outdoor atmospheres were sampled at residential and work places. The eventual goal of this study is to identify potential health risks of airborne pollutants. The size-dependent distributions of various elements and source apportionment of aerosol particulate matter was determined. Sampling was done using a multi-stage cascade impactor capable of sorting sizes with aerodynamic cut-off diameters ranging from 16 to .0625 micro-m in 9 steps. The samples collected on membrane filters, were studied using X-ray fluoresce (XRF), micro-XRF, Scanning Electron Microscopy (SEM), and optical microscopy. Results obtained so far show the main two sources of particulate matter pollutants are: airborne desert dust and airborne dust from building materials. Trace elements on the other hand are related to industrial pollution. Microscopy methods show that mass concentration of fine particles is considerably higher than that of coarse particles. Elemental analysis obtained with micro-XRF show that Ca, Si, Al, and Fe are present on all membranes but dominant on large cut-off membranes ( > 2 micro-m) while Si, P, Zn, S, Cu, K, and Ti are found on small cut-off membranes (< 1 micro-m). Elements appearing in trace quantities are: Zn, Fe, Cu, Br, Pb, Mn and mainly attributed to industrial pollution. It is noted that Ti, for example, is found mainly indoors possibly resulting from wall paints. On the other hand, elements such as Mg, Na, Cl, are originating from sea salts and hence are found both indoors and outdoors. Future work is underway to include complimentary methods such as ion beam techniques such as Proton Induced X-ray Emission(PIXE) and Proton Induced Gamma-ray Emission (PIGE) to identify lighter elements and synchrotron X-ray Absorption Spectroscopy( XAS) for chemical analysis.