Project Details Conceptualization of definition and classification for humic substances

Project No.:
Start Date:
17 January 2022
End Date:


The goal of this project is to develop definition of humic substances in terms of systems chemistry. For reaching the goal, firstly, we will explore the modern concepts of systems chemistry; secondly, we will overview the modern literature to identify the general and unique molecular features inherent within the humic systems; thirdly, we will explore the existing practices of classification of HS; and fourthly, we will summarize the existing ways to generate quantitative descriptors of their structure. We will use the acquired knowledge to elaborate chemical definition and classification of humic substances and to classify the existing analytical methodologies.


Carbon accounting is crucial for reliable estimates of anthropogenic impact on climate change. Organic carbon is the most labile carbon pool composed predominantly of humified non-living organic matter. It is the major natural emitter of carbon dioxide and methane. At the same time, ill-defined isolation protocols and a lack of rigorous chemical definition of the humic systems provide for large uncertainties in assessing the rate of natural degradation and turnover of non-living organic matter. The humic systems exist both in soils, water, and organic rocks. While in all solid substrates, such as soil, coal, peat, etc., they are referred to as humic substances (HS), the non-living organic matter in waters is referred to as natural organic matter (NOM). Both HS and NOM play crucial ecological roles, in particular, under conditions of global climate change and represent different varieties of humic systems. Development of molecular systematics for these complex chemical systems is a prerequisite for reliable carbon accounting on different scales. The major problem is that in contrast to living systems, the synthesis of humic systems has no genetic code. It proceeds stochastically being constrained by the specific environmental parameters such as temperature, pressure, concentration of oxygen, humidity, the presence of aqueous, mineral, or organic matrices, etc. As a result, both definition and classification of humic systems are operationally defined according to the protocols of their isolation and fractionation. There is an ample experimental evidence that behind this operational classification are structural regularities governing this behavior. However, they are not used yet for developing molecular systematics of HS and NOM, which are the different varieties of humic systems.

Specific objectives of the proposed work are as follows:
– critical evaluation of recent developments in the field of systems chemistry aimed at conceptualization of HS and NOM as complex chemical system
– critical evaluation of existing analytical methodologies for investigation structural and molecular space of humic systems,
– critical evaluation of existing approaches to classification of non-living organic matter (e.g., humic substances, natural organic matter, dissolved organic matter, soil continuum, soil organic matter, aquatic continuum)
– evaluation of recent developments in the field of quantitative description of structure of HS and NOM aimed at recommendations of best structural descriptors
– elaboration of algorithm to compile the existing (reported) data on molecular composition of HS and NOM into chemical library of humic systems
– elaboration of principles of molecular systematics of humic systems
– elaboration of chemical definition and classification of humic substances
– clear descriptions of relatively simple and inexpensive analytical measurements by which a sample could be properly classified for a use by small industrial companies – humate producers.


Jan 2022 update – A Thematic session is planned for at the 21st International Conference of the International Humic Substances Society – Sept 17-22, 2022.

Announcement published in Chem Int April 2022, p. 26

Page last update 8 Apr 2022