Humic acid is a prinicipal component of humic substances which are major organic constituents of soil (humus), peat, coal, many upland streams dystrophic lakes and ocean water. It is produced by biodegradation of dead organic manure. It is not a single acid, rather, it is a complex mixture of many different acids containing carboxyl and phenolate groups. So that the mixture behaves functionally as a dibasic acid.