Identification of Contaminants and Toxins in Soils

Large Area Mapping (Hypermaps) using SEM-XRF can be performed on samples with topography. That is, minimal sample preparation is required and the sample can be analyzed directly without any degredation. This is particularly relevant in the analysis of soils, where any form of sample preparation, such as mounting and polishing or carbon coating, may alter the specimen. The micro-XRF can analyze soil samples directly, as shown in Fig. 1. This includes major elements but also trace elements or trace mineral phases that may incorporate contaminants or toxins (see Fig. 2). In this example, grains containing Pb and As contaminants are identified.

Fig. 1: Large area X-ray map (120 mm x 30 mm) of soils (Analytical parameters: tube voltage Rh at 50 kV, anode current 600 µA, pixel spacing 25 µm). Top row from left to right: Total X-ray intensity map (similar to a BSE image, grey) of four soil samples. Second row from left to right: K (purple) and Ca (yellow). Third row from left to right: Ti (orange) and Mn (blue). Bottom row from left to right: Fe (red) and F1 (grey).
Fig. 2: Analysis of soil sample confirming the presence of Pb (right) in sample 4. Bottom images show the spectra from the sample confirming the identification of Pb and As in the sample.