Figure 7
(a) Visible light image of the black stains region analyzed from the dark region. (b) RGB composite of SR µXRF maps of Hg (red), Cl (green) and S (blue) [step size (h × v), 4 × 4 μm; map size (h × v), 800 × 800 μm; exp. time, 100 ms/pixel; energy: 2.825 keV]. The magenta color indicates the region where mercury and sulfur signals overlap, following the shape of the black stain. (c) Macro-XANES spectra recorded at S K-edge (average of 45 spectra) of white, medium-dark and dark regions. Peak at 2.4737 keV corresponds to the sulfides (S-II), peak at 2.4777 keV to the sulfites (SIV) and peak at 2.4839 keV to the sulfates (SVI). It is worth noting that the intensity of the white region (blue line), before normalization, is almost zero, meaning that S is less concentrated in the white sample. (d) Detail of RGB composite of SR µXRF maps of Hg (red), Cl (green) and S (blue). (e) Selected AOI for hyperspectral 2D µXRF maps at S K-edge. The RGB composite image obtained by selecting ROIs in the hyperspectral dataset shows the distribution of sulfides (S-II) and sulfates (SVI) species.
