Semi-quantitative analysis of changes in soil coatings by scanning electron microscope and energy dispersive X-ray mapping

Abstract

Scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDX) has been used extensively with soils and sediments. The method of obtaining X-ray spectrums at single points on samples has two shortcomings; (1) it is limited to a particular point and (2) it is primarily a qualitative measure indicating the presence or the absence of specific elements. The relative number of X-ray counts from one element as compared to another may provide limited semi-quantitative analysis. The objective of this study was to present a SEM/EDX mapping technique where different samples may be quantitatively compared to one another. This technique provides X-ray counts from thousands of points on the sample in a short time (less than one hour). The X-ray counts were normalized to silica and the surfaces of different samples were compared regarding the presence and the distribution of different elements. A T-test at α=0.05 showed that results from this technique were precise for soil samples. Digitized images as well as frequency curves were obtained to show the distribution of each of the analyzed elements on the sample surface.