Humic substances - compounds of still unknown structure: applications in agriculture, industry, environment, and biomedicine

Abstract

Humic substances as part of humus-soil organic matter-are compounds arising from the physical, chemical and microbiological transformation (humification) of biomolecules. They are important because they constitute the most ubiquitous source of non-living organic material that nature knows. Approximately 80% of the total carbon in terrestrial media and 60% of the carbon dissolved in aquatic media are made up of humic substances. Humic substances have important roles in soil fertility, and are considered to have primal relevance for the stabilization of soil aggregates. They can be divided into three components according to their solubility: humic acids, fulvic acids and humin. Humic acids are the most explored group of humic substances. Beyond their relevance for life these substances have industrial applications in the development of absorbents to be used at the sources of metal-poisoning. Being natural substances, their purification process is cheaper than the synthesis of any other sorbent and, moreover, due to their high operability, they absorb more than the absorbents used to date, such as active charcoals or clays. The specific properties of humic acid products enable their application in industry, agriculture, environmental and biomedicine.

Characteristics of dissolved organic matter in the inflows and in the outflow of Lake Võrtsjärv, Estonia

“…Humic substances (HS) accounting for 40-90% of the DOC pool in various surface waters belong to the refractory fraction of DOM (Frimmel, 1998;Pena-Méndez et al, 2005;Tulonen, 2004). The HS are divided into three fractions: fulvic acids (FA), humic acids (HA), and humins.…”

Influences of humic acids and photoreactivation on the disinfection of Escherichia coli by a high-power pulsed UV irradiation

“…can be used to activate plant-related microbe communities in soil and to accelerate the growth of a variety of plants [31,32]. This growthpromotion effect was apparent in fresh water, but was not so obvious in growth medium.…”

Binding and setting of kaolin based materials with natural organic acids

“…These different groups can bind strongly with the mineral matter. Peña-méndez and Havel (2005) describe humic-like substances as a polyaromatic core surrounded with aliphatic chains. Nevertheless, it is difficult to describe HS with a general formula because of their maturation over time, which leads to a polycondensation of HS and a modification of the structure.…”