Abstract:

Sorption and desorption characteristics of two phenolic acids, phydroxybenzoic acid and benzoic acid, in the rhizosphere soil of continuous cropping poplar plantations were investigated in order to find accumulation mechanism of the phenolic acids. An isotherms adsorption and desorption method and HPLC test were used. The results showed that rhizosphere soil of poplar plantation had strong adsorptive capacity to phydroxybenzoic acid and benzoic acid. The average adsorption rate of benzoic acid in the rhizosphere soil acid was from 39.53% to 47.46%, which was lower than that of phydroxybenzoic acid with an average adsorption rate from 63.39% to 72.26%. Fruendlich isotherms adsorption equation well described the adsorption process of those two phenolic acids in poplar rhizosphere soil, and there existed a significant linear relation between C_e (adsorption equilibrium concentration) and C_s (absorbance). The adsorption of those two phenolic acids belonged to physical adsorption. But, phydroxybenzoic acid had a stronger desorption capacity in different poplar plantation rhizosphere soil and the average desorption rate was from 46.62% to 52.89%. In comparison, the desorption rate of benzoic acid was lower, especially in balanced adsorption solution at high concentration. This rule was in accordance with the adsorption constant in the rhizosphere soil of different poplar generation. The sorption and desorption of those two phenolic acids reflected the property of environmental behavior in rhizosphere soil and could interpret accumulation of the phenolic acids in poplar rhizosphere soil.

Key words: poplar rhizosphere, phydroxybenzoic acid, benzoic acid, sorption and desorption, environmental behavior, accumulation mechanism