Soluble organic acids and their chelating influence on Al and other metal dissolution from forest soils

The effects of mineral acid deposition on chemical properties of leachates of three granitic forest soils and pine O₁-litter were investigated under controlled laboratory conditions. Of the array of organic acids released from litter and SOM as detected by HPLC analysis, nine compounds were identified and six compounds have been quantified. Organic acids possessing certain functional group arrangements, such as di- and tri-carboxylic acids containing β-hydroxyl groups, and phenolic acids with ortho-hydroxyls were about three to ten times faster in dissolving Al than similar organics with other functional group combinations or mineral acids at comparable pH and concentration levels. There was little correlation between the initial pH of chelating organic acid input solution and rate of metal dissolution. On a mole metal-leached per gram basis, dissolution of metals from Shaver soil followed the order Al>Mn>Fe in both organic and mineral acids.