Table 1.
Chemical properties of soil HAs and FAs (data for HAs previously reported in Boguta and Sokołowska [27]).
Fig 1.
Thermogravimetric curves (TG) with first derivatives (dTG) of exemplary FAs and HAs.
Table 2.
TG, MS and DSC characteristics of soil HAs and FAs at temperature ranges R1, R2 and R3.
Fig 2.
Curves of differential scanning calorimetry (DSC) and first derivatives (dDSC) of exemplary FA and HA.
Table 3.
Experimental and reference data of weight loss at individual temperature ranges for humic and fulvic acids of different origin and for various conditions of thermogravimetric measurements.
Fig 3.
The distribution of the ion current (IC) of the main m/z intensities for (a) FA1 and (b) HA1.
Fig 4.
FTIR 3D spectrum of the evolved gases of FA3 as a function of temperature.
Table 4.
Frequencies and relationships between the main, characteristic FTIR bands of the gaseous products of thermal decomposition at the maximum temperatures of the DSC effects in R1, R2 and R3 temperature ranges.
Fig 5.
FTIR 2D spectra of FA4 (a, c) and HA4 (b, d) for characteristic temperatures of R1, R2 and R3 intervals.
Fig 6.
Exemplary relationships between TG-DSC-QMS-FTIR parameters and chemical properties of FAs and HAs (a) N content and C/N ratio vs. m/z = 17 area at R3; (b) COOH and O content vs. m/z = 18 area at R2; (c) COOH content vs. m/z = 44 area at R1, R2 and R3; (d) COOH content and E2/E6 ratio vs. HTD index.
Table 5.
Coefficients of person’s correlations calculated between selected chemical properties of HAs and FAs and the parameters obtained from TG, DSC and MS.
Bold digits highlight statistically significant relationships (p = 0.05).