乙草胺、丁草胺和异丙甲草胺在室外天然水中的非生物降解及其影响因素
Abiotic degradation and influencing factors of acetochlor, butachlor and metolachlor in different waters under natural conditions
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摘要: 在亚热带冬、夏两季室外自然光照和温度条件下,研究了环境浓度下乙草胺、丁草胺和异丙甲草胺在河水和海水基底中的非生物降解(水解+光解)行为,并结合室内实验研究了非生物降解的影响因素.室外实验结果表明,冬季(气温12.30—26.98 ℃,平均17.47 ℃)乙草胺、丁草胺和异丙甲草胺在河水中的非生物降解半衰期(t1/2)为64—131 d、水解t1/2为105—346 d、光解t1/2为159—410 d,海水中非生物降解t1/2为89—193 d、水解t1/2为77—277 d、光解t1/2为417—630 d;夏季(气温20.77—30.37 ℃,平均27.22 ℃)3种目标农药在河水中非生物降解t1/2为4—20 d、水解t1/2为7—54 d、光解t1/2为7—32 d,海水中非生物降解t1/2为10—50 d、水解t1/2为23—67 d、光解t1/2为17—192 d.目标农药在海水中的残留持久性远高于河水;超纯水条件下,光解在目标农药的非生物降解中占主导地位;河水中的光解速率快于海水.室内实验发现,硝酸盐促进了3种目标农药的水解,同时对乙草胺和丁草胺的光解也起到促进作用;pH升高促进了异丙甲草胺的水解和光解速率,但是抑制了丁草胺的水解和乙草胺、丁草胺的光解;腐殖质添加浓度为10 mg·L-1和20 mg·L-1时促进了3种目标农药的水解,但在浓度达30 mg·L-1时则抑制了乙草胺的水解及异丙甲草胺的光解.总体而言,3种目标农药在实际水环境中的降解半衰期均较长,其降解机理和毒性效应值得进一步研究.Abstract: Abiotic degradation (photolysis and hydrolysis) and its influence factors of three widely-used amide herbicides, acetochlor, butachlor and metolachlor in river water and seawater were studied under both natural and indoor controlled conditions. Outdoor results indicated that in winter season (temperature 12.30—26.98 ℃, average 17.47 ℃) the half-lives of acetochlor, butachlor and metolachlor in river water were 64—131 d for abiotic degradation, 105—346 d for hydrolysis, and 159—410 d for photolysis, while in sea water the corresponding half-lives were 89—193 d, 77—277 d and 417—630 d, respectively. In summer season (temperature 20.77—30.37 ℃, average 27.22 ℃), the corresponding half-lives were 4—20 d, 7—54 d and 7—32 d in river water, and 10—50 d, 23—67 d and 17—192 d in sea water. Target pesticides showed longer stability in sea water than in river water. Photolysis played predominant roles in abiotic degradation and photolysis rates in river water were faster than those in sea water. Under indoor controlled conditions, NO3- and NO-2 were found to promote the hydrolysis process and the photolysis rates of acetochlor and butachlor. High pH accelerated metolachlor's hydrolysis and photolysis, but inhibited butachlor's hydrolysis and photolysis of acetochlor and butachlor. Humic acids at low concentrations of 10 mg·L-1 and 20 mg·L-1 enhanced the hydrolysis process, but inhibited hydrolysis of acetochlor and photolysis of metolachlor at high concentration of 30 mg·L-1. In summary, acetochlor, butachlor and metolachlor are all relatively persistent in aquatic environment, and their degradation mechanisms and toxic effects deserve further study.
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Key words:
- amide herbicides /
- abiotic degradation /
- hydrolysis /
- photolysis /
- river water /
- seawater
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