環境Q&A

No.12580 【A-1】

Re:フミン酸のこと

2005-09-28 15:56:43 無鉄砲 （

>Humic acid is the soluble part of humic substance at acidic condition, and the solubility of humic acid dcreases as pH.

前半と後半でおそらく反対のことを言っています（後半をand the solubility of humic acid decreases as pH decreases.と解釈）。
以下は、ネット上に存在する記述の代表例です。
よって、前半は、Humic acid is the insoluble part of humic substance at acidic condition,が正しいでしょう。

http://www.bbe-moldaenke.de/english/news_sept03_e.htm
Humic acid is the fraction of humic substances that is not soluble in water under acid condition (below pH 2) but soluble at a higher pH. It is the collective name for the acid radical found in humic matter. Humic acid is insoluble in water, any acid solution, methyl ethyl ketone and methyl alcohol. Humic acids are thought to be complex aromatic macromolecules with amino acids, amino sugars, peptides, aliphatic compounds involved in linkages between the aromatic groups.

http://www.mdpi.org/ijms/papers/i3101048.pdf
Humic substances (HS) are ubiquitous in the environment. They are formed during the microbiological and abiotic transformations of animal and plant materials. Among them, humic acid (HA) is the fraction of HS that is not soluble in water under acidic conditions (pH < 2) but is soluble at higher pH, with average molecular weight of 2,000 to 3,000. Fulvic acid (FA) is the fraction that is soluble at all pH values, with average molecular weight less than 1,000.

http://www.terre-et-eau.univ-avignon.fr/Base_webographique/w_white/Chapter14.pdf
Humic substances in waters are divided into fulvic acid and humic acid. The definition of these two is again analytical. Humic acids are defined as those humic substances that precipitate when the solution is acidified with HCl to a pH of 1. Fulvic acids are those substances remaining in solution at this pH.