外源酚酸在杨树人工林土壤中的吸附与滞留动态研究

Study on Adsorption and Retention of Exogenous Phenolic Acids in the Soil of Poplar (Populus deltoids Marsh) Plantation

采集不同连作代数杨树人工林土壤样品,采用外源添加酚酸的方法结合HPLC定量测定,研究了对羟基苯甲酸和苯甲酸在杨树人工林土壤中的吸附动态和滞留规律,探讨了两种酚酸在杨树人工林土壤中的累积机制。结果表明:(1)两种酚酸在杨树人工林土壤中的吸附可大致分为两个过程,即快速吸附阶段和慢吸附阶段,对羟基苯甲酸的快速吸附阶段大约在16h内完成,而苯甲酸约需24h。达到吸附平衡时,对羟基苯甲酸在土壤中的平均吸附率为58.78%,苯甲酸的平均吸附率为37.07%。(2)杨树人工林土壤对两种酚酸均具有较强的吸附能力,达到吸附平衡时,对羟基苯甲酸在土壤中的平均吸附量为2483.19μg/g,苯甲酸为1377.51μg/g,对羟基苯甲酸的吸附能力强于苯甲酸。(3)Langmuir动力学方程和一级动力学方程是描述两种酚酸在土壤中吸附过程的最优模型。(4)酚酸滞留量检测结果表明,酚酸添加15d后,对羟基苯甲酸在土壤中的残留率为4.3%～5.2%,而苯甲酸的残留率仅为1.3%～1.7%。两种酚酸在土壤中的滞留动态可以用准二级动力学方程进行描述,对羟基苯甲酸的消除半衰期平均为4.24d,苯甲酸消除半衰期平均为2.61d,对羟基苯甲酸在土壤中的滞留期长于苯甲酸。(5)两种酚酸的吸附与滞留行为与土壤有机质、金属离子、土壤质地等性质关系密切,微生物数量也是决定酚酸在土壤中滞留能力的重要因素。

The adsorption and retention of allelochemicals in soil colloid are vital factors to their distribution and accumulation.The fate of allelochemicals is closely related to the sorption and degradation in rhizosphere soil.Two phenolic acids,p-hydroxybenzoic acid and benzoic acid,found in the extracted solution of rhizosphere soil from poplar（Populus deltoids Marsh） plantation,took on significant accumulation in continuous cropping plantations.To detect their accumulation mechanism in soil,we studied their adsorption and retention characteristics by exogenous addition.Soil samples were collected from different generation of poplar plantation lands and the amount of adsorption and retention of exogenous phenolic acids was detected by HPLC.The results showed that,the adsorption process of two phenolic acids could be divided into two stages,quick sorption and slow sorption.The quick sorption of p-hydroxybenzoic acid lasted about 16 hours,while benzoic acid could last about 24 hours.When adsorption equilibrium reached,The average adsorption rate of benzoic acid in poplar rhizosphere soil acid was 37.07% and that of p-hydroxybenzoic acid was 58.78%.Two phenolic acids had large adsorptive capacity on soil colloid of poplar plantaions.The average adsorption of p-hydroxybenzoic acid with 2 483.19 μg/g was more than benzoic acid with 1 377.51 μg/g when adsorption equilibrium reached.If using some models to describe the adsorption process of two phenolic acids in the soils of poplar plantation,we found Langmuir kinetic equation and first-class kinetic equation were the best models.The retention experiment showed that,the retention rate of p-hydroxybenzoic acid was 4.3%～5.2% and benzoic acid was only 1.3%～1.7% at 15th day after exogenous addition in soil.The retention process of two phenolic acids can be described by second kinetic equation.The retention half-time of p-hydroxybenzoic acid in popular rhziosphere soils was 4.24 d,while benzoic acid was 2.61 d,indicating p-hydroxybenzoic acid was more easily accumulated.The adsorption and retention behavior in poplar platation soils indicated to some extent the accumulation mechanism of those two phenolic acids.The adsorption and retention of two phenolic acids were close to soil properties such as the content of organic matter and metal ions,soil texture.The abundance of microbes was also important factor deciding the retention ability of phenolic acids in soil.