Behavior of phenolic substances in the decaying process of plants

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Abstract
The relationship between the elution of heavy metals with phenolic substances and the chemical structure of phenolic substances, as well as the interaction between phenolic substances and metals were studied using batch and column methods. The elution of3 metals (Fe, Al and Mn) with 4 phenolic acids (p-hydroxybenzoic, salicylic, α-resorcylic, and protocatechuic acids) and phthalic acid were investigated using 3 different soils. The results are as follows: 1) The elution of heavy metals was largely influenced by the chemical structures of the Phenolic acids. Protocatechuic, salicylic, and phthalic acids which had different chelating sites easily extracted iron, aluminum, and manganese from the soils. Hydroxybenzoic and α-resorcylic acids which had no chelating sites contributed little to the elution process. 2) In many cases, protocatechuic acid showed a stronger affinity to iron than to aluminum, ut salicylic acid showed the opposite trend. The affinity of phthalic acid to metals was much less than that of both phenolic acids. 3) The elution of heavy metals was also influenced by the soil pH. The amounts of heavy metals eluted with protocatechuic acid increased as the soil pH increased. The amounts eluted With salicylic and phthalic acids increased as the soil pH decreased. 4) The results suggested that chelating phenolics such as protocatechuic and salicylic acids, Which Were exuded from plant residues or produced during the decaying process of plant residues, eluted heavy metals such as iron, aluminum and manganese from soil particles and accelerated the downward movement of these metal ions.