Fig. 2

NEXAFS spectra of PS, PET and PP fragments retrieved from agricultural and road-sided soil, all NEXAFS data were normalized to pre- and post-edge to remove the effect of the sample thickness on the optical density. A Average spectrum of each group determined by hierarchical clustering for a single stack measurement acquired on a fragment. The colour of the lines indicates the region of the stack that was used to compute the average (see line B for the depth the spectra were measured). The colour of the arrow in A indicates the position of the peaks presented in the same colour in B. B Intensity against depth plot of the peaks highlighted by the arrow in A along the surface – BM gradient of the same stack measurement on the fragment shown in A. The coloured bar shows the position of the cluster group presented in A in the surface – BM gradient. C Average intensity of the peaks highlighted by the arrow in A along the surface – BM for all replicate stack measurements acquired on the same plastic fragment. The coloured ribbon indicates the standard deviation around the mean for each peak intensity. The three different panels (A, B, C) are chosen to illustrate the chemical changes indicated by the spectrum peak position and intensity in the depth gradient (A), the depth on which the changes occur in the material (B), and finally the heterogeneity of the above cited parameters occurring around the surface of a same fragment illustrated by the replicate measurements (C)