Development of an x-ray method for mineralogical analysis of Africa soils using a benchtop diffractometer

Abstract

Soil mineralogy is a principal determinant of many soil functional properties that are expensive and time consuming to measure, and can in turn determine soil agricultural, engineering and environmental qualities. Africa soil mineralogy has however not been adequately and appropriately researched upon. This is because of poorly and fragmentally coordinated scientific investigations coupled with the limitations in the traditional analytical techniques. Recent developments in instrument designs and capabilities, and launch of bench-top X-ray Diffractometers (XRD) have widened the possible application areas for high- throughput X-ray diffraction (XRD) as a powerful complementary tool for soil screening. This study was conducted to develop a high precision and rapid through put protocol for X-ray diffraction analysis and demonstrate its ability to make reliable and accurate measurement of Africa soil mineralogy, using a Bruker D2 PHASER benchtop diffractometer. A multiphase soil sample was investigated for independent evaluation of the analysis accuracy, presenting the sample preparation and mounting techniques used. A further 160 diverse set of top soils samples selected from the sentinel sites of the African Soils Information Services (AfSIS) project was used to develop a generalizable approach, and to test the applicability of the protocol developed. With only half-hour scanning time, the method developed produced high quality diffractograms that could reliably be matched to possible known patterns from the powder diffraction files, taking XRD from what has been largely time consuming and specialized measurement, to a rapid and simple method that can be used for routine analysis of soil mineralogy by soil testing laboratories.