【作者】 何玲；

【导师】 朱优峰； 王秀丽；

【作者基本信息】 浙江大学 ， 环境工程（专业学位）， 2020， 硕士

【摘要】 2,4-二氯苯氧丙酸(DCPP)和2甲4氯丙酸(MCPP)是典型的手性苯氧丙酸除草剂,尽管在土壤中降解相对迅速,但仍在许多国家的地表水和地下水中频繁检出。它们的对映体一般具有不同的环境行为,因此需要在手性层面研究其在环境中的降解转化。不少文献报道了手性苯氧丙酸除草剂在环境介质中降解时的对映体选择性,但关于环境因素对其对映体选择性降解影响的研究仍比较有限。本文研究了合肥森林土和宁波菜地土在不同初始浓度(1 mg/kg和10 mg/kg)、含水率(田间持水量(water holding capacity,WHC)的30%、60%和125%)和温度(4℃、25℃和40℃)条件下分别降解Rac-DCPP和Rac-MCPP时的对映体选择性、稳定性碳同位素分馏和微生物群落结构及多样性。主要结果如下:(1)初始浓度降低、含水率增加和温度升高时,两种土壤中Rac-DCPP和Rac-MCPP的降解速率均增大。除4℃,1 mg/kg,60%WHC外,其余培养条件下Rac-DCPP和Rac-MCPP在两种土壤中的降解均符合一级动力学反应模型,降解半衰期分别为3.4～17.7 d和3.3～28.7 d。(2)不同初始浓度、含水率和温度条件下,两种土壤中Rac-DCPP降解时均是S-DCPP被优先降解,但其对映体选择性的强弱不同:初始浓度增加、含水率降低和温度升高时,Rac-DCPP在合肥森林土中的对映体选择性均增强,而在宁波菜地土中均减弱。(3)不同初始浓度、含水率或温度条件下,土壤中Rac-MCPP降解时的对映体选择性不同:两种土壤在1 mg/kg,60%WHC,25℃时均为R-MCPP的优先降解,而在10 mg/kg,60%WHC,25℃时均为S-MCPP的优先降解;合肥森林土在30%WHC,1 mg/kg,25℃时优先降解S-MCPP,而125%WHC,1 mg/kg,25℃时优先降解R-MCPP;宁波菜地土在4℃,1 mg/kg,60%WHC和40℃,1mg/kg,60%WHC时分别优先降解S-MCPP和R-MCPP。(4)除合肥森林土10 mg/kg,60%WHC,25℃下的Rac-MCPP组及宁波菜地土10 mg/kg,60%WHC,25℃和30%WHC,1 mg/kg,25℃下的Rac-DCPP和Rac-MCPP组外,其余培养条件下Rac-DCPP和Rac-MCPP降解时均会发生明显的稳定性碳同位素分馏,其碳同位素富集因子ε=-1.68‰～-4.25‰,表观碳同位素效应AKIE=1.017～1.040,表明降解过程中有C-H键氧化断裂的发生。(5)与空白对照相比,宁波菜地土中添加Rac-DCPP和Rac-MCPP后,Sphingomonadaceae和Xanthomonadaceae的相对丰度均显著增加;合肥森林土添加Rac-DCPP后,除10 mg/kg,60%WHC,25℃外,其余条件下Sphingomonadaceae的相对丰度均显著增加,而添加Rac-MCPP后,Sphingomonadaceae的相对丰度仅在40℃,1 mg/kg,60%WHC下显著增加。(6)不同初始浓度、含水率或温度条件下,土壤中Rac-DCPP或Rac-MCPP培养时的微生物群落结构存在显著差异。初始浓度和含水率增加时,合肥森林中Rac-DCPP组的物种多样性都增大,Rac-MCPP组均减少;宁波菜地土中RacDCPP组的物种多样性均减少,而Rac-MCPP组在前者降低,在后者升高。两种土壤中Rac-DCPP和Rac-MCPP组的物种多样性随温度的升高均下降。更多还原

【Abstract】 2,4-dichlorophenoxypropionic acid(DCPP)and 2-methyl-4-chloropropionic acid(MCPP)are typical chiral phenoxypropionic acid herbicides.Although they relatively rapidly degrade in soil,they are frequently detected in surface water and groundwater in many countries.Their enantiomers generally have different environmental behaviors,so it is necessary to study their degradation and transformation in the environment at the chiral level.Many literatures reported the enantioselectivity degradation of chiral phenoxypropionic acid herbicides in environmental media,but the effect of environmental factors on enantioselective degradation is still limited.In this paper,under different initial concentration(1 mg/kg and 10 mg/kg),moisture content(30%,60% and 125% of water holding capacity(WHC))and temperature(4 ℃,25 ℃ and 40 ℃)conditions,the enantioselectivity degradation,stable carbon isotope fractation,microbial community composition and diversity in Hefei forest soil and Ningbo vegetable soil when incubated with Rac-DCPP and RacMCPP respectively were studied.The main results are as follows:(1)When initial concentration decreased,moisture content increased and temperature increased,the degradation rates of Rac-DCPP and Rac-MCPP in the two soils increased.Except for 4℃,1 mg/kg,60% WHC,under other incubation conditions,the degradation of Rac-DCPP and Rac-MCPP in the two soils fitted the first-order kinetic reaction model,and the degradation half-lives were 3.4 ～ 17.7 d and 3.3 ～ 28.7 d,respectively.(2)Under different initial concentration,moisture content and temperature conditions,S-DCPP was preferentially degraded in the two soils during Rac-DCPP degradation,but its degree of enantioselectivity was different: when initial concentration increased,moisture content decreased and temperature increased,the enantioselectivity of Rac-DCPP in Hefei forest soil both enhanced,while it weakened in Ningbo vegetable soil.(3)Under different initial concentration,moisture content or temperature conditions,the enantioselectivity of Rac-MCPP during degradation in soils was different: the two soils were preferential degradation of R-MCPP at 1 mg/kg,60% WHC,25℃,while were preferential degradation of S-MCPP at 10 mg/kg,60% WHC,25℃;in Hefei forest soil,S-MCPP was preferentially degraded at 30% WHC,1 mg/kg,25℃,and R-MCPP was preferentially degraded at 125% WHC,1 mg/kg,25℃;in Ningbo vegetable soil,S-MCPP and R-MCPP were preferentially degraded at 4℃,1 mg/kg,60% WHC and 40℃,1 mg/kg,60% WHC,respectively.(4)Except for Hefei forest soil when incubated with Rac-MCPP at 10 mg/kg,60% WHC,25℃ and Ningbo vegetable soil when incubated with Rac-DCPP and RacMCPP at 10 mg/kg,60% WHC,25℃ and 30% WHC,1 mg/kg,25℃ respectively,significant stable carbon isotope fractionation occurred under other incubation conditions,the carbon isotope enrichment factor ε =-1.68‰ ～-4.25‰,and the apparent carbon isotope effect AKIE = 1.017 ～ 1.040,which indicated that oxidative cleavage of C-H bonds occurred during the degradation process.(5)Compared with controls,the relative abundances of Sphingomonadaceae and Xanthomonadaceae both significantly increased in Ningbo vegetable soil when incubated with Rac-DCPP and Rac-MCPP;in Heifei forest soil,the relative abundance of Sphingomonadaceae significantly increased after Rac-DCPP addition except for 10 mg/kg,60% WHC,25℃,and after Rac-MCPP addition,the relative abundance of Sphingomonadaceae only significantly increased at 40℃,1 mg/kg,and 60% WHC.(6)Under different initial concentration,moisture content or temperature conditions,the microbial community structure in Rac-DCPP or Rac-MCPP incubated soil was significantly different.When initial concentration and moisture content increased,in Hefei forest soil,the species diversity of Rac-DCPP group increased,and the Rac-MCPP group decreased;in Ningbo vegetable soil,the species diversity of RacDCPP group decreased,while the Rac-MCPP group decreased in the former and increased in the latter.The species diversity of the Rac-DCPP and Rac-MCPP groups in the two soils decreased with increasing temperature.更多还原