Abstract
We describe the development of a simple standardization technique for the x-ray diffraction (XRD) analysis of atmospheric particulate matter, using aluminium oxide as an internal standard. Accuracy and precision were better than ± 25% for nearly all the typical atmospheric crystalline compounds studied. Good agreement was found with elemental analyses. Detection limits were around 40–75 μg, depending on the compound, for scan times of about 1-h. This represents a considerable improvement in speed of analysis over previous studies. The suitability of various filters for XRD analysis was assessed. Efforts were made to minimize potential sample modification during and after sampling, and tests made to examine hydration effects. The representativity of the collected samples to actual atmospheric conditions is discussed. The technique was applied to size-fractionated atmospheric samples collected in suburban Toronto, Canada. Around half the collected mass was XRD identifiable, of which about half evidently originated from blown dust (soil, building materials, road salt, etc.) with the remainder comprising some eight pollution derived compounds of NH
4
+, SO
4
2−, NO
3
−, Cl
− and Pb. The distribution of the major ions between different compounds was determined. XRD identifiable lead was related to total Pb concentrations. We conclude by considering our results in a wider context by examining the similarities and discrepancies between other related studies worldwide.