Maris Klavins


Humic substances are high molecular weight refractory polycationites formed during decay of living organic matter and through biosynthesis of low molecular weight organic substances (metabolites or decay products of living organisms). Presence of many functional groups in the structure of humic substances determines their ability to interact with metal ions forming stable complexes and influencing metal ion speciation in the environment and mobility, behaviour and speciation forms in the environment. Presently humic substances are a product of industrial scale and quantities in amounts of hundreds of tons are produced. The aim of this study is to analyse derivatization possibilities of humic substances. To achieve this aim derivatization of humic substances using acylation (at first introduction of acetylgroups, but also changing length acyl chains are considered) are used. Also alkylation is used. Mild oxidation can help to obtain modified products with reduced molecular weight. Another approach includes introduction of new functional groups and structures. To achieve this aim, conjugates with short peptides, amines and sugar derivatives using coupling with water-soluble carbodiimides are obtained. As basic characteristics elemental analysis as well as functional analysis have been used, supported with Fourier transform infrared (FTIR), 13C nuclear magnetic resonance spectrometry and other methods. Derivatives of humic substances containing sulpho, amino, and hydroxylgroups and thiolgroups were synthesized and their properties were analyzed in respect to their their elemental composition; functional group content changes in spectral characteristics. The derivatives of humic substances showed significant differences in the number and in ability to interact with the metal ions, which were reflected in their complexation properties towards metal ions. FTIR spectra gave evidence of the presence of metal ions, strongly bound and protected in inner sphere complexes. The obtained derivatives of humic substances can be used for remediation of environment contaminated with heavy metal ions.


humic substances; modification; functional groups; pollutants; remediation

Full Text:



C. Zaccone, G. Casiello, F. Longobardi, L. Bragazza, A. Sacco, and T. M. Miano, “Evaluating the ‘conservative’behavior of stable isotopic ratios (d13C, d15N, and d18O) in humic acids and their reliability as paleoenvironmental proxies along a peat sequence”, Chemical Geology, vol. 285, no. 1-4, p. 124, 2011.

H. Rydin and J. K. Jeglum,The biology of peatlands. Oxford, OUP, 2013.

T. Sharkey, “Estimating the rate of photorespiration in leaves”, Physiologia Plantarum, vol. 73, no. 1, p. 147, May 1988.

T. Sharkey, “Discovery of the canonical Calvin-Benson cycle”, Photosynthesis Research, vol. 53, p. 835, 2018.

J. Carter and V. Barwick, Good Practice Guide for Isotope Ratio Mass Spectrometry, FIRMS, 2011.

J. M. McDermott, J. S. Seewald, C. R. German, and S. P. Sylva, “Pathways for abiotic organic synthesis at submarine hydrothermal fields”, Proceedings of the National Academy of Sciences, vol. 112, no. 25, p. 7668, 2015.

G. J. Retallack, “Cenozoic Expansion of Grasslands and Climatic Cooling”, The Journal of Geology, vol. 109, no. 4, p. 407, July 2001.

M. H. O’Leary, “Carbon Isotopes in Photosynthesis”, BioScience, vol. 38, no. 5, p. 328, 1988.

D. Robinson, L. Handley, and C. Scrimgeour, “A theory of 15N/14N fractionation in nitrate-grown vascular plants”, Planta, vol. 205, no. 3, p. 397, 1998.

Z. He, M. Xu, G. Y. Qiu, and J. Zhou, “Use of 15N stable isotope to quantify nitrogen transfer between mycorrhizal plants”, Journal of Plant Ecology, vol. 2, no. 3, p. 107, 2009.

D. Robinson, “d15N as an integrator of the nitrogen cycle”, Ecology & Evolution, vol. 16, no. 3, p. 153, March 2001.

I. I. Lishtvan and N. T. Korol, Basic properties of peat and methods for their determination, Nauka I Tehnika, Minsk, 1975.

Stevenson, F.J. Humus Chemistry. Genesis, Composition, Reactions, second ed. John Wiley & Sons, Inc., New York, N.Y., 1994.

Leenheer, J.A. Progression from model structures to molecular structures of natural organic matter components. Ann. Environ. Sci., 2007, vol. 1, p. 57-68.

Tessier, A., Campbell, P.G.C., Bisson, M. Sequential Extraction Procedure for the Speciation of Particulate Trace Metals. Anal. Chem., 1979, vol. 51, N 7, p. 844-851.

Tipping, E. Cation Binding by Humic Substances. Cambridge: University press, New York, 2002.



  • There are currently no refbacks.