Organic Matter
Michael J. Kennish in Ecology of Estuaries Physical and Chemical Aspects, 2019
Humic substances represent the end products of the decomposition of plant and animal tissues by bacteria and fungi (Figure 3). Most humic material in river and estuarine waters is derived from terrestrial sources via the leaching of soil and from aquatic sources via in situ exudation and degradation products of plants.28,44-46 Four pathways exist for the formation of soil humic substances (Figure 4). While early workers thought that humic substances were modified lignins (Pathway 4 in Figure 4), present-day investigators support the now popular polyphenol theory (Pathways 2 and 3) based on condensation reactions involving polyphenols and quinones. Schematic representations of the lignin and polyphenol theories of humus formation are illustrated in Figures 5 and 6, respectively. According to the lignin theory, microorganisms incompletely utilize lignin, with the residuum yielding humic and fulvic acids. In the polyphenol theory, large molecules are derived from low-molecular-weight organic compounds through condensation and polymerization.2 In spite of the popularity of the polyphenol theory, all four pathways shown in Figure 4 may operate in all soils and should be considered as viable mechanisms for the synthesis of humic and fulvic acids.
Radionuclide Concentrations in Soils lution-Processed Organic Solar Cells
Michael Pöschl, Leo M. L. Nollet in Radionuclide Concentrations in Food and the Environment, 2006
Humic substances such as humic acid (HA) and fulvic acid (FA) are a fraction of the organic matter in a soil. These have a high affinity for actinide and lanthanide metal ions in a terrestrial system. Chung et al. [17] investigated the possibility of retaining fallout radionuclides in an organic matter-rich soil of Jeju Island, Korea. In order to simulate the behavior of actinide metals, Eu(III) was used as a tracer. Synchronous fluorescence spectroscopy (SyFS) was used to characterize the Eu(III) binding to humic substances. The element composition of HA and FA (carbon, hydrogen, nitrogen, and sulfur) was determined by a combustion method.
Carbohydrate-derived fulvic acid wellness drink: its tolerability, safety and effect on disease markers in pre-ART HIV-1 positive subjects
Published in South African Family Practice, 2018
ME Botes, IS Gilada, JR Snyman, JPL Labuschagne
Humic substances are present wherever organic matter is decomposing.8–10 Humic substances can be defined as: ‘a general category of naturally occurring, biogenic, heterogeneous organic substances that can generally be characterized as being yellow to black in colour and of high molecular weight’. Humic substances can be subdivided into humic acid (HA), fulvic acid (FA) and humin. The average molecular weight of humic substances may range from 500 to 5 000 Da for FA and 3 000 to 1 000 000 Da for HA.9 These substances are characterised on the basis of their solubility in water as a function of pH. FA is the fraction that is soluble in water under all pH conditions. In general, FA is also lower in molecular size and weight and lower in colour intensity than the HA. The novel medicinal properties and applications of HA and FA have been researched over many decades for various applications.8,9
The toxicology of air pollution predicts its epidemiology
Published in Inhalation Toxicology, 2018
Andrew J. Ghio, Joleen M. Soukup, Michael C. Madden
Humic substances (HS) are ubiquitous, heterogeneous, amorphous, organic materials occurring in all terrestrial and aqueous environments including composts, sediments, peat bogs, coals, rivers, lakes, and oceans (Stevenson, 1985). The molecular weights for HS can range from a few hundred to millions of daltons. Chemically, they are a complex mixture of many different acids with prominent numbers of carboxylate and phenolate groups (Figure 1). HS include three different fractions: humic acid, fulvic acid and humin. Humic acid is the major extractable component of soil HS; it is insoluble in water under acidic conditions (pH <2) but soluble at higher pH values and dark brown to black in color. Fulvic acid is that fraction of HS soluble in water under all pH conditions and remains in solution after removal of humic acid by acidification; it is light yellow to yellow-brown in color. Humin is the fraction of HS that is not soluble in water at any pH value and is black in color.
Formulation design, optimization and in vivo evaluation of oral co-encapsulated resveratrol-humic acid colloidal polymeric nanocarriers
Published in Pharmaceutical Development and Technology, 2021
Rahul Hasija, Sundeep Chaurasia, Swati Gupta
Humic acid (HA) falls under the category of humic substances as an affluent resource of shilajit, and the most governing fraction of natural organic matters (Kong et al. 1987; Acharya et al. 1988). Humic substances are omnipresent: in the soil, in the river and in the sewage water, and macromolecular negatively charged polyelectrolytes. Intensive studies have highlighted humic substances as constituent components which are primarily comprised of humus approximately 60%–80% and other components such as benzoic acid, hippuric acid, fatty acid, ellagic acid, resin, triterpenes, sterols, aromatic carboxylic acid, amino acids, 3–4 benzocoumarins, and phenolic lipids (Agarwal et al. 2007; 2010). The average molecular weight of the HA is reported to be 6500 Da (Ghosal 2003). HA serves as a potent bioenhancer for poorly water-soluble active molecules. HA consists of dark brown to blackish colour and is insoluble under acidic conditions (pH < 2) but freely soluble at higher pH.
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