An improved procedure for the X-ray diffraction analysis of low-mass atmospheric dust samples

Dust particles collected by air filtration are separated from their filter by ultrasonic agitation before being concentrated by ultracentrifugation, followed by their deposition by piping onto a ceramic tile to induce orientation of the clay fraction. Scans are performed by XRD using a position-sensitive detector and a collimated incident beam. Semi-quantitative treatment of the data is carried out using reference intensity factors determined from field samples. The results obtained by this procedure on some Saharan dust samples are in agreement with those deduced from their bulk chemical analysis.