Cheluviation

Organic acids have the ability to dissolve soil minerals, and can destroy silicate minerals and iron and aluminum oxides, so that metal ions are precipitated and complexed with organic complexing agents through ion exchange, surface absorption, and chelation-reaction mechanisms. For example, at low pH, a large number of metal ions are complexed with organic acids. When the organic acid occupies the coordination position of the metal ion, it can prevent the precipitation and crystallization of the metal oxide and increase its solubility. Conversely, at high pH (e.g. 7–8), dissolved metal ions, such as Fe(III), will precipitate out of the solution as insoluble complexes. == Eluviation of chelate compounds ==

The eluviation of chelate compounds is the downward movement of soil chelates. The eluviation of chelate compounds can be affected by: • Acidity. Organic acids produced under acidic conditions can increase the solubility of metal elements such as iron and aluminum, thereby enhancing soil eluviation. Iron and aluminum are easily leached at low pH. As the pH increases, ferric hydroxide and aluminum hydroxide compounds precipitate. Under oxidative conditions, metal ions are easily precipitated, and the chelate is easily polymerized, thereby separating the chelate from the metal ions. • Soil texture. Clay has a certain adsorption capacity for chelates, which weakens the leaching of complexes. On the other hand, soils with a coarse texture and water-saturated soils will likely enhance the leaching effect of chelates. ==References==