Sorption and retention of phenolic acids in soil of poplar plantation in eastern China

Adsorption and retention on soil particles are vital behaviors affecting the amount of allelochemicals in soil, which perhaps results in their accumulation. To investigate the accumulation mechanism of three phenolic acids i.e. p-hydroxybenzoic acid, benzoic acid and cinnamic acid, which existed in the soil of poplar (Populus Sect. Aigeiros Duby) plantation, we studied their sorption and retention properties by exogenous application. The controlled experiments indicated the adsorption process of three phenolic acids in soils could be divided into two stages, quick sorption and slow sorption. Three exogenous phenolic acids had large adsorptive capacity on soils of poplar plantations. Langmuir kinetic equation and first-class kinetic equation were the optimum models to describe the adsorption process. The retention dynamics showed the amount of three phenolic acids decreased over incubation time. This processes could be described by secondary kinetic equation. The retention half-life of p-hydroxybenzoic acid was about 4.24 d, while benzoic acid and cinnamic acid was only about 2.61 d and 1.29 d, and the residue rate of p-hydroxybenzoic acid was 4.3~5.2% and benzoic acid was only 1.3~1.7% at 15th day. While, the residual ratio of cinnamic acid in soil was only about 3.52% and was completely eliminated for 9 days. These results indicated that cinnamic acid was more easily eliminated and while p-hydroxybenzoic acid was more easily accumulated.