Keywords: humic substance, fulvic acids, humic acids, FTIR spectroscopy, PCA, principal component analysis, ICA, independent component analysis, 2DMAP, two-dimensional mapping, lake sediment, marine sediment, soils, Antarctic seawater
Fourier transform infrared spectroscopic investigation of humic substance samples of different origin and typology supported by chemometric tools
In this paper 198 FTIR spectra of humic substance (HS) extracted from lake, marine sediments, soils and by Antarctic seawater were examined by Principal Component Analysis (PCA), Independent Component Analysis (ICA) and Two-dimensional Mapping (2DMAP) to identify the compositional and structural characteristics which characterise the typologies of samples examined and which are hardly detectable by means of an ordinary visual examination of FTIR spectra. PCA was able to characterise the HS fraction with the highest amount of polymerised molecules consisting of humic acids (HA) essentially. 2DMAP allowed a direct qualitative comparison among different typologies of HS samples. At last, ICA application showed that HS samples are characterised by structures where the humification process is supported by polymerisation reactions and in addition by formation of supramolecular compounds arising from polar (hydrogen bond) and non-polar (Van der Walls) interactions among the several biomolecules present.