CONTENT Vol. 2 - Humus.ru

15th IHSS Meeting- Vol. 2
techniques: principal component analysis (PCA) and partial least square analysis (PLS) with
an Orthogonal Signal Correction (OSC) of the data. Particularly interesting was the score
scatter plot (figure 2) of the first two components, in which the samples were grouped
according to the different treatments: Casein, Cellulose, Control, Lignin and Tripalmitin. This
plot revealed, within the different groups, a trajectory depending on the different time
experiments (time effect). Moreover the group of Tripalmitin is completely isolated from the
rest of observation exhibiting complete different chemical properties; instead the Casein and
Cellulose groups manifest a strong homogeneity each other like the control and Lignin
groups. These chemical affinities and the time effect were analyzed with the Van Krevelen
diagram (figure 3). In the different plots were pointed out the various chemical spaces (CHO,
CHOS, CHON, CHONS), which visually highlight specific cluster series of elementary
compositions observed within nominal masses.
Figure 1. Bottom to up: 13 C NMR spectra of matrix left, matrix+soil S at incubation time 0, 3
weeks and 1 year; matrix at left is lignin, matrix at right is casein.
Figure 2. PLS-OSC analysis: Score scatter plot with all the spectra. Observations are grouped
according to the different class delaying similar chemical properties.
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