Correlation of humic substances chemical properties and their thermo-oxidative degradation kinetics
- 76 Downloads
Application of the Arrhenius equation as the temperature function in modeling of the degradation kinetics of humic substances brought a high positive Pearson correlation coefficient with the carbon content and a reasonable negative correlation with the oxygen content. Ratio C/H indicating the aromaticity degree of humic samples did not show any significant correlation. Relatively high value of correlation coefficients provided also O + N and ratios C/(O + N) and C/O, respectively. In contrast, H, N content and natural and heat generated free radical content and their ratio gave substantially lower correlation coefficients. The latter indicates that free radicals are probably not the main reason of the collapse of the secondary structure of humic substances leading to their degradation.
KeywordsHumic substances Isoconversional methods Single step approximation Correlation analysis Thermal analysis
The financial support of Grant Agency of the Czech Republic, Project 104/05/P513 and Ministry of Education, Project MSM 0021630501 are acknowledged.
- 6.Francioso O, Montecchio D, Gioacchini P, Ciavatta C. Thermal analysis (TG-DTA) and isotopic characterization (13C-15N) of humic acids from different origins. Appl Biochem. 2005;20:537–44.Google Scholar
- 11.Stevenson FJ. Humus chemistry. Genesis, compositions, reactions. 2nd ed. NY: Wiley and Sons, Inc; 1994.Google Scholar
- 15.Siewert C. Rapid screening of soil properties using thermogravimetry. Soil Sci Soc Am J. 2004;68:1656–61.Google Scholar
- 16.Siewert C. Investigation of the thermal and biological stability of soil organic mater. Aachen: Shaker-Verlag; 2001.Google Scholar
- 17.Pekař M, Kučerík J. Thermoanalytical approach to study soil dynamics. In: Zaujec A, Bielek P, Gonet SS, editors. Humic substances in ecosystems, vol 6, Bratislava; 2005, p. 130.Google Scholar
- 18.Kislinger J, Kučerík J. Relationship between soil respiration and kinetic parameters of thermo-oxidative degradation. In: Szpoganicz B, et al., editors. Livro de resumos do VII EBSH. Brasil: Florianopolis; 2007, p. 5.Google Scholar
- 21.Barančíková G, Klučáková M, Madaras M, Makovníková J, Pekař M. Chemical structure of humic acids isolated from various soil types and lignite. In: Humic substances in the environment, vol 3, Bratislava; 2003, p. 3.Google Scholar
- 25.Benites VM, Kučerík J, Madari BE. Thermal analysis of humic substances extracted from contrasting pedoenvironments. Chem Listy. 2005;99s:123–5.Google Scholar
- 26.Novák F, Kalousková N, Machovič V, Brus J. Composition and structure of fulvic acids from B-Horizon of Ferro-humic Podzol in Trojmezí (Bohemian Forest). J For Sci. 1999;45:554–65 (In Czech).Google Scholar
- 36.Klein E, Lukeš V. DFT/B3LYP study of the substituent effect on the reaction enthalpies of the individual steps of sequential proton loss electron transfer mechanism of phenols antioxidant action: Correlation with phenolic C-O bond length. J Mol Struct THEOCHEM. 2007;805:153–60.CrossRefGoogle Scholar