Humic acid

Humic acid is one of the major components of humic substances which are dark brown and major constituents of soil organic matter humus that contributes to soil chemical and physical quality and are also precursors of some fossil fuels. They can also be found in peat, coal, many upland streams, dystrophic lakes and ocean water. Humic substances make up a large portion of the dark matter in humus and consist of heterogeneous mixtures of transformed biomolecules exhibiting a supramolecular structure , that can be separated in their small molecular components by sequential chemical fractionation (Piccolo, 2002; Fiorentino et al., 2006). Since the end of the 18th century, humic substances have been designated as either humic acid, fulvic acid or humic fractions are defined strictly on their solubility in either acid or alkali, describing the materials by operation only, thus imparting no chemical information about the extracted materials.