1、Green Humic Acid and its Possible Origin as a Fungal Metabolite

Humic acids usually show an almost featureless absorption curve in which optical density increases with decreasing wavelength over the visible scale.

2、Addressing Coloration Caused by Humic Substances (Humus)

When turning mountain stream water into a public water supply, one challenge that often troubles water treatment engineers is the presence of colored substances known as humic substances.

3、The chemical nature of the green fraction of P type humic acid

On gel filtration of P typc humic acid, thc second dark brown humic acid fraction cluted prior to thc third green fraction (Pg) has an absorption spectrum almost identical to the latter.

4、The irreversible transformation of the molecular structure of humic

Humic acid (HA) is an important component of natural organic matter, and understanding the nature and environmental behavior of HA is essential for advancing water treatment technologies and environmental remediation strategies.

5、Chemistry of Humic Acids and Related Pigments

Humic acids and related pigments, collectively referred to as humic substances, are widely distributed in soils, natural waters, marine and lake sediments, peat bogs, carbonaceous shales, lignites, brown coals and other miscellaneous deposits [1–5].

Green Humic Acid and its Possible Origin as a Fungal

port 1 The chemical nature of the green fraction of P type . acid. Soil Science and Plant Nutrition, 1967, 13, 121-122. 1.9 42 2 Humus composition of mountain soils in Central. Japan with special reference to the distribution of . d. Soil Science and Plant Nutrition, 1967, 13, 151-158. 1.9 . 166 3 Nature and Distribut.

Green Humic Acid and its Possible Origin as a Fungal Metabolite

Work in Japan (personal communication) suggests a possible relationship to a perylene quinone. It may be related to a pigment previously isolated from irregular olive green patches in Australian lateritic and podzolic soils.

Studies on the colour of humic acids: Part 1 on the concepts of humic

Accordingly the colour tone of humic acids should be regarded as an aspect of the essential properties of humic acids, and it might qualify as a measure of distinguishing the individual humic acids.

The chemical nature of the green fraction of P type humic acid

Its unusual spectral characteristics are due to a green fraction (Pg), which can be separated from the humic acid dissolved in aqueous alkali by chromatography on Sephadex or cellulose powder, and is precipitated as a reddish-brown substance on acidification (2).

STUDIES ON THE COLOUR OF HUMIC ACIDS

Abstract Based on their solubility, humus has been often divided into three fractions, i.e. fulvic acids, humic acids and humins. On the other hand, it seems to be generally accepted that humus can be divided into two groups (1) (2), non-humic substances and humic substances.

There are numerous factors contributing to the green discoloration of humic acid. The following are potential causes:

1. Oxidation Reactions: When humic acid comes into contact with oxygen, oxidation reactions may occur, leading to a green hue. This happens because oxygen converts certain components in humic acid into corresponding oxides, altering its color.

2. Microbial Activity: Metabolic byproducts generated by microorganisms in humic acid during the decomposition of organic matter can cause green discoloration. For example, some bacteria and fungi produce sulfides while breaking down humus, which impart a greenish tint.

3. Temperature Changes: Higher temperatures generally intensify the green color of humic acid. This is due to accelerated oxidation of organic materials within humic acid under heat, promoting color changes.

4. pH Variations: The acidity or alkalinity of the environment affects humic acid’s color. Acidic conditions tend to green the substance, while alkaline conditions lean toward yellow. Different pH levels alter the properties and reactivity of specific components in humic acid.

5. Light Exposure: Prolonged sunlight exposure triggers photochemical reactions in humic acid, resulting in green discoloration. Light may also speed up oxidative or reductive processes, further modifying its color.

6. Moisture Content: The water content in humic acid influences its color. Higher moisture levels typically result in lighter colors, while lower moisture leads to darker hues. This depends on how water affects the solubility and dispersion of humic acid components.

7. Soil Composition: Soil mineral content impacts humic acid’s color. Soils rich in minerals darken humic acid, whereas organic-rich soils favor greenish tones due to variations in component properties and reactions.

8. Plant Growth Conditions: Soils with denser root systems often produce darker humic acid, while sparse roots yield lighter colors. Plant activity affects organic matter decomposition rates, influencing color.

9. Soil pH: Soil pH directly impacts humic acid’s color. Acidic soils (lower pH) promote greenish hues, while alkaline soils (higher pH) shift toward yellow. pH-driven changes in component reactivity drive this effect.

10. Soil Moisture: Soil humidity affects color intensity. Wetter soils darken humic acid, while drier conditions lighten it, as moisture modulates solubility and dispersion of its constituents.

The green discoloration of humic acid arises from a combination of factors, which must be contextually analyzed. In practice, observing and experimenting can identify specific causes, allowing targeted measures to control and improve humic acid quality.