红壤性水稻土-上覆水系统毒死蜱消解的室内模拟实验

Chlorpyrifos dissipation in a red soil-developed paddy soil′s soil-overlying water system:A laboratory incubation experiment

以我国南方红壤丘陵区稻田土壤为对象,通过60 d的室内模拟培养实验,研究了毒死蜱在水稻土-上覆水系统中的消解与转化规律。加药后,15、25℃和40℃条件下上覆水中毒死蜱均在前期快速消解,后期消解速率逐渐降低,符合一级动力学方程。3种温度处理下上覆水中毒死蜱的半衰期DT50(0.70~1.01 d)和消解速率常数(0.6888~0.9852 d^(-1))差异较小。毒死蜱投加之后,易转化成3,5,6-三氯-2-吡啶醇(TCP),在上覆水中发生累积。转化受温度影响显著,经过60 d的培养,40℃时17.3%~25.5%的毒死蜱转化为TCP。表层(0~3 cm)土壤中毒死蜱的积累受温度影响显著,未灭菌处理在15、25℃和40℃下,表层土壤中毒死蜱的残留量分别为163.66、80.29 mmol▪kg^(-1)和34.95 mmol▪kg^(-1),约为其初始投加含量的57.38%、28.15%和12.25%。总之,土壤-上覆水系统中,在第60 d时,投加的毒死蜱中仅0.39%~2.24%滞留在上覆水中,10.18%~58.32%迁移到土壤中,0.47%~25.53%降解为TCP存在于上覆水中。总体而言,毒死蜱在上覆水中的残留率较低,在土壤中残留率较高且主要为表层土壤所吸附,温度与微生物对毒死蜱的消解具有协同作用。

A 60-day laboratory microcosm experiment was conducted with paddy soil collected from the hilly,red soil area of southern China.The dissipation and transformation of chlorpyrifos in the paddy soil’s overlying water system were studied.After application,chlorpyrifos in the overlying water at 15,25℃,and 40℃ dissipated rapidly during the early stage,gradually decreasing in the later stage.The dynamics of chlorpyrifos in the overlying water conformed to first-order kinetics.The half-life(0.70~1.01 d)and digestion rate constant(0.6888~0.9852 d^(-1))of chlorpyrifos in the overlying water were similar at the three tested temperatures.The added chlorpyrifos was easily converted into 3,5,6-trichloro-2-pyridinol(TCP)and accumulated in the overlying water.Chlorpyrifos degradation was significantly affected by temperature.After 60 d of incubation,17.3%~25.5%of chlorpyrifos was degraded into TCP at 40℃.The accumulation of chlorpyrifos in the surface soil(0~3 cm)was significantly affected by temperature.In the unsterilized treatment,the chlorpyrifos residue in the surface soil at 15,25℃,and 40℃ was 163.66,80.29 mmol·kg^(-1)and 34.95 mmol·kg^(-1),respectively,approximately 57.38%,28.15%and 12.25%of the initial amount of chlorpyrifos added,respectively.Overall,in the soil-overlying water system,only 0.39%~2.24%of the added chlorpyrifos remained in the overlying water after 60 d,10.18%~58.32%migrated into the soil,and 0.47%~25.53%degraded into TCP in the overlying water.The residual rate of chlorpyrifos in the overlying water was lower than that in the soil,and its enrichment in the surface layer was distinct.Temperature and microorganisms synergistically affect chlorpyrifos dissipation.