环境因子对土壤中二氯喹啉酸降解的影响

Effects of environmental factors on the degradation of quinclorac in soil

为明确环境因素对土壤中二氯喹啉酸降解的影响,以华南地区水稻田土壤为对象,测定其在不同温度、湿度和pH值条件下的降解速率和半衰期。二氯喹啉酸按照1 mg·kg-1的剂量进行添加。不同处理的土壤被放置在各自的培养环境中,1 h,1、3、7、14、21、30、45、60、120 d后取样。用高效液相色谱法对二氯喹啉酸进行定量分析。结果表明：pH值对二氯喹啉酸的降解影响最为明显,中性环境下（pH=7.0）降解最为迅速,半衰期为10.58 d,碱性环境下（pH=8.0）的半衰期为18.53 d,酸性环境下（pH=6.0）降解最慢,半衰期为30.81 d;温度对其降解存在一定影响,在5~25℃范围内,温度升高,二氯喹啉酸降解加快,（25±0.5）℃的半衰期为15.04 d,（35±0.5）℃的半衰期为17.33 d;湿度对二氯喹啉酸的降解无明显促进作用,30%、60%、90%湿度条件下,其半衰期分别为24.32、20.69和25.77 d。因此,调节土壤pH值为中性或在25~35℃范围内施用二氯喹啉酸有利于其降解,可减少其残留和药害的发生。

The degradation rate of quinclorac was investigated to afford scientific basis for its rational application with paddy soil of South China at different temperature,humidity and pH value.Quinclorac was sprayed into soil at the concentration of 1 mg·kg-1.The soils were placed in corresponding temperature condition.Soil samples were taken for analysis on 1 h and 1,3,7,14,21,30,45,60,120 d and extracted with potassium hydroxide solution.The supernatant was cleaned up with methylene dichloride and was evaporated on a rotary evaporator.Quinclorac was analyzed by high performance liquid chromatography.The results showed that pH value was the most obvious impact factor,the degradation rate of quinclorac was the fastest at pH = 7.0 and the half-life is 10.58 d.The degradation rate of quinclorac at pH = 7.0 was followed by alkaline（pH = 8.0） and acidic soil（pH = 6.0） and the half-lives are 18.53 and 30.81 d,respectively.Quinclorac degraded faster with higher temperature at 5-25 ℃.The half-lives at（25±0.5） ℃ and（35±0.5） ℃ were 15.04 d and 17.33 d,respectively.Humidity had little effect to promote the degradation of quinclorac and the half-lives were more than20 d at 30%,60%,90%.Therefore,adjusting the pH value of paddy soil to 7 or applying quinclorac in warm seasons 25-35 ℃ are beneficial to its degradation,which causes less residue and phytotoxicity.