模拟日光照射下土霉素的复合光化学转化动力学及环境归趋
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摘要
环境水体中存在众多可解离的有机污染物,而不同的解离形态表现出相异的环境行为,如光化学反应活性和归趋.本文以土霉素(OTC)为例,研究了水中可解离化合物的表观光降解、光氧化等复合光化学转化动力学,并揭示了其相应的环境光化学归趋和贡献.模拟日光(λ>290nm)照射下,OTC的光降解遵循准一级反应动力学,光解速率常数(k)对pH表现出明显的依赖性.这是由于随pH值升高,解离形态(i)从OTCH_2~0、OTCH~-到OTC~(2-)渐变,相应的k_i和量子产率(Φ_i)显著增大.竞争动力学实验进一步表明,·OH和~1O_2均可以氧化降解OTC,且降解速率随着pH的增大而加快.这与3种解离形态不同的去质子化程度和氧化反应活性有关.去质子化增加化合物的电子密度,利于活性氧物种的亲电攻击,从而促进光氧化反应.基于以上OTC解离形态的不同光化学转化活性,评估了环境表层水体(pH=6~9)中的复合光化学转化半减期(t_(1/2,E)).t_(1/2,E)值依赖于基质pH和季节,北纬45°晴天正午,t_(1/2,E)在0.131 h(仲夏,pH=9)到3.63 h(仲冬,pH=6)之间.多数情况下,OTC的表观光解是其最主要的光化学转化途径,~1O_2氧化次之,而·OH氧化的贡献非常小.以上结果证明了OTC不同解离形态具有不同的光化学转化动力学.因此,为了准确评价水环境中抗生素等可解离有机污染物的光化学归趋和风险,有必要综合考虑所有解离形态的复合光化学行为.
Many ionizable organic pollutants are present in the aqueous environment.They are of great concern because their environmental behavior( e.g.,photochemical reactivities and fate) is highly dependent on different dissociation forms. In this study,we adopted oxytetracycline( OTC) as a case to investigate the kinetics of multivariate photochemical reactions,apparent photolysis and photooxidation,and to reveal the corresponding environmental photochemical fate.It was observed that the photodegradation followed the pseudo-first-order kinetics under simulated solar irradiation( λ > 290 nm). The photolytic rate constants( k) obviously depended on the solution pH,due to the changes of dissociation forms( from OTCH_2~0 to OTCH~- and OTC~(2-)) with the increasing pH. OTC~(2-)photolysis is the fastest and had the highest photolytic efficiency,followed by OTCH~-and OTCH_2~0. Competition kineticexperiments indicated that OTC was oxidized by ·OH and ~1O_2,and the reaction was facilitated by the increasing pH.This pH dependence is attributed to the diverse deprotonation degrees and photooxidation reactivities of the 3 dissociation forms. Deprotonation can enhance the electron donating ability,decrease the steric hinerance,and hence facilitate the reactions of OTC with reactive oxygen species. Furthermore,the environmental multivariate phototransformation half-lives( t_(1/2,E)) were dependent on matrix pH and seasons,ranging from 0.131 h at pH 9 in summer to 3.63 h at pH 6 in winter at 45° N latitude.Among the multivariate photochemical processes,apparent photolysis is the most dominant,followed by ~1O_2 and ·OH oxidation. This study confirmes that different dissociation species of OTC have distinct phototransformation kinetics.Thus,to better understand the photochemical fate and risk of ionizable organic pollutants( e.g.,antibiotics) in surface waters,the effects of acid-base dissociation and multiple photoreactions should be considered.
Many ionizable organic pollutants are present in the aqueous environment.They are of great concern because their environmental behavior( e.g.,photochemical reactivities and fate) is highly dependent on different dissociation forms. In this study,we adopted oxytetracycline( OTC) as a case to investigate the kinetics of multivariate photochemical reactions,apparent photolysis and photooxidation,and to reveal the corresponding environmental photochemical fate.It was observed that the photodegradation followed the pseudo-first-order kinetics under simulated solar irradiation( λ > 290 nm). The photolytic rate constants( k) obviously depended on the solution pH,due to the changes of dissociation forms( from OTCH_2~0 to OTCH~- and OTC~(2-)) with the increasing pH. OTC~(2-)photolysis is the fastest and had the highest photolytic efficiency,followed by OTCH~-and OTCH_2~0. Competition kineticexperiments indicated that OTC was oxidized by ·OH and ~1O_2,and the reaction was facilitated by the increasing pH.This pH dependence is attributed to the diverse deprotonation degrees and photooxidation reactivities of the 3 dissociation forms. Deprotonation can enhance the electron donating ability,decrease the steric hinerance,and hence facilitate the reactions of OTC with reactive oxygen species. Furthermore,the environmental multivariate phototransformation half-lives( t_(1/2,E)) were dependent on matrix pH and seasons,ranging from 0.131 h at pH 9 in summer to 3.63 h at pH 6 in winter at 45° N latitude.Among the multivariate photochemical processes,apparent photolysis is the most dominant,followed by ~1O_2 and ·OH oxidation. This study confirmes that different dissociation species of OTC have distinct phototransformation kinetics.Thus,to better understand the photochemical fate and risk of ionizable organic pollutants( e.g.,antibiotics) in surface waters,the effects of acid-base dissociation and multiple photoreactions should be considered.
引文
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Cooper W J,Zika R G,Petasne R G,et al.2009.Sunlight-induced photochemistry of humic substances in natural waters:major reactive species[J].Advances in Chemistry,219(1):333-362
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Edhlund B L,Arnold W A,Mc Neill K.2006.Aquatic photochemistry of nitrofuran antibiotics[J].Environmental Science&Technology,40(17):5422-5427
Ge L K,Chen J W,Wei X X,et al.2010.Aquatic photochemistry of fluoroquinolone antibiotics:Kinetics,pathways,and multivariate effects of main water constituents[J].Environmental Science&Technology,44(7):2400-2405
Ge L K,Na G S,Chen C E,et al.2016.Aqueous photochemical degradation of hydroxylated PAHs:Kinetics,pathways,and multivariate effects of main water constituents[J].Science of the Total Environment,547:166-172
Ge L K,Na G S,Zhang S Y,et al.2015.New insights into the aquatic photochemistry of fluoroquinolone antibiotics:Direct photodegradation,hydroxyl-radical oxidation,and antibacterial activity changes[J].Science of the Total Environment,527-528C:12-17
葛林科,任红蕾,鲁建江,等.2015.我国环境中新兴污染物抗生素及其抗性基因的分布特征[J].环境化学,34(5):875-883
Jiao S J,Zheng S R,Yin D Q,et al.2008.Aqueous oxytetracycline degradation and the toxicity change of degradation compounds in photoirradiation process[J].Journal of Environmental Sciences,20:806-813
Jin X,Xu H,Qiu S,et al.2017.Direct photolysis of oxytetracycline:Influence of initial concentration,p H and temperature[J].Journal of Photochemistry and Photobiology A:Chemistry,332:224-231
Knapp C W,Cardoza L A,Hawes J N,et al.2005.Fate and effects of enrofloxacin in aquatic systems under different light conditions[J].Environmental Science&Technology,39(23):9140-9146
Larson R A,Weber E J.1996.Reaction mechanisms in environmental organic chemistry[J].Carbohydrate Polymers,29(3):293-294
Latch D E,Packer J L,Stender B L,et al.2005.Aqueous photochemistry of triclosan:Formation of 2,4-dichlorophenol,2,8-dichlorodibenzo-pdioxin,and oligomerization products[J].Environmental Toxicology and Chemistry,24(3):517-525
Leifer A.1988.The Kinetics of Environmental Aquatic Photochemistry:Theory and Practice[M].Washington,DC:American Chemical Society
Luo Y,Xu L Q,Rysz M,et al.2011.Occurrence and transport of tetracycline,sulfonamide,quinolone,and macrolide antibiotics in the Haihe River Basin,China[J].Environmental Science&Technology,45(5):1827-1833
MatykiewiczováN,KlánováJ,Klán P.2007.Photochemical degradation of PCBs in snow[J].Environmental Science&Technology,41(24):8308-8314
Mill T.1999.Predicting photoreaction rates in surface waters[J].Chemosphere,38(6):1379-1390
Na G,Fang X,Cai Y,et al.2013.Occurrence,distribution,and bioaccumulation of antibiotics in coastal environment of Dalian,China[J].Marine Pollution Bulletin,69(1/2):233-237
Na G S,Gu J,Ge L K,et al.2011.Detection of 36 antibiotics in coastal waters using high performance liquid chromatography-tandem mass spectrometry[J].Chinese Journal of Oceanology and Limnology,29(5):1093-1102
Niu J F,Li Y,Wang W L.2013.Light-source-dependent role of nitrate and humic acid in tetracycline photolysis:Kinetics and mechanism[J].Chemosphere,92(11):1423-1429
Qiang Z,Adams C.2004.Potentiometric determination of acid dissociation constants(p Ka)for human and veterinary antibiotics[J].Water Research,38(12):2874-2890
Vione D,Minella M,Maurino V,et al.2014.Indirect photochemistry in sunlit surface waters:Photoinduced production of reactive transient species[J].Chemistry-A European Journal,20(34):10590-10606
Wei R C,Ge F,Huang S Y,et al.2011.Occurrence of veterinary antibiotics in animal wastewater and surface water around farms in Jiangsu Province,China[J].Chemosphere,82:1408-1414
Wei X X,Chen J W,Xie Q,et al.2013.Distinct photolytic mechanisms and products for different dissociation species of ciprofloxacin[J].Environmental Science&Technology,47(9):4284-4290
Werner J J,Arnold W A,Mc Neill K.2006.Water hardness as a photochemical parameter:Tetracycline photolysis as a function of calcium concentration,magnesium concentration,and p H[J].Environmental Science&Technology,40(23):7236-7241
Xie Q,Chen J W,Zhao H X,et al.2013.Different photolysis kinetics and photooxidation reactivities of neutral and anionic hydroxylated polybrominated diphenyl ethers[J].Chemosphere,90(2):188-194
Xu H,Cooper W J,Jung J,et al.2011.Photosensitized degradation of amoxicillin in natural organic matter isolate solutions[J].Water Research,45(2):632-638
杨常青,王龙星,侯晓虹,等.2012.大辽河水系河水中16种抗生素的污染水平分析[J].色谱,30(8):756-762
Yang X H,Xie H B,Chen J W,et al.2013.Anionic phenolic compounds bind stronger with transthyretin than their neutral forms:Nonnegligible mechanisms in virtual screening of endocrine disrupting chemicals[J].Chemical Research in Toxicology,26(9):1340-1347
张翠,胡学锋,骆永明.2016.模拟太阳光下水中土霉素的光化学降解[J].环境化学,35(3):430-438
Zhang Q Q,Ying G G,Pan C G,et al.2015.A comprehensive evaluation of antibiotics emission and fate in the river basins of china:Sourceanalysis,multimedia modelling,and linkage to bacterial resistance[J].Environmental Science and Technology,49(11):6772-6782
Ziolli R L,Jardim W F.2003.Photochemical transformations of watersoluble fraction(WSF)of crude oil in marine waters:A comparison between photolysis and accelerated degradation with Ti O2using GC-MS and UVF[J].Journal of Photochemistry and Photobiology A:Chemistry,155(1):243-252
Bodrato M,Vione D.2014.APEX(Aqueous photochemistry of environmentally occurring xenobiotics):a free software tool to predict the kinetics of photochemical processes in surface waters[J].Environmental Science:Processes&Impacts,16(4):732-740
Boreen A L,Arnold W A,Mc Neill K.2004.Photochemical fate of sulfa drugs in the aquatic environment:Sulfa drugs containing fivemembered heterocyclic groups[J].Environmental Science&Technology,38(14):3933-3940
Boreen A L,Arnold W A,Mc Neill K.2005.Triplet-sensitized photodegradation of sulfa drugs containing six-membered heterocyclic groups:Identification of an SO2extrusion photoproduct[J].Environmental Science&Technology,39(10):3630-3638
Chen K,Zhou J L.2014.Occurrence and behavior of antibiotics in water and sediments from the Huangpu River,Shanghai,China[J].Chemosphere,95(5):604
Cooper W J,Zika R G,Petasne R G,et al.2009.Sunlight-induced photochemistry of humic substances in natural waters:major reactive species[J].Advances in Chemistry,219(1):333-362
DolinováJ,R 7)u6icˇka R,KurkováR,et al.2006.Oxidation of aromatic and aliphatic hydrocarbons by OH radicals photochemically generated from H2O2in ice[J].Environmental Science&Technology,40(24):7668-7674
Edhlund B L,Arnold W A,Mc Neill K.2006.Aquatic photochemistry of nitrofuran antibiotics[J].Environmental Science&Technology,40(17):5422-5427
Ge L K,Chen J W,Wei X X,et al.2010.Aquatic photochemistry of fluoroquinolone antibiotics:Kinetics,pathways,and multivariate effects of main water constituents[J].Environmental Science&Technology,44(7):2400-2405
Ge L K,Na G S,Chen C E,et al.2016.Aqueous photochemical degradation of hydroxylated PAHs:Kinetics,pathways,and multivariate effects of main water constituents[J].Science of the Total Environment,547:166-172
Ge L K,Na G S,Zhang S Y,et al.2015.New insights into the aquatic photochemistry of fluoroquinolone antibiotics:Direct photodegradation,hydroxyl-radical oxidation,and antibacterial activity changes[J].Science of the Total Environment,527-528C:12-17
葛林科,任红蕾,鲁建江,等.2015.我国环境中新兴污染物抗生素及其抗性基因的分布特征[J].环境化学,34(5):875-883
Jiao S J,Zheng S R,Yin D Q,et al.2008.Aqueous oxytetracycline degradation and the toxicity change of degradation compounds in photoirradiation process[J].Journal of Environmental Sciences,20:806-813
Jin X,Xu H,Qiu S,et al.2017.Direct photolysis of oxytetracycline:Influence of initial concentration,p H and temperature[J].Journal of Photochemistry and Photobiology A:Chemistry,332:224-231
Knapp C W,Cardoza L A,Hawes J N,et al.2005.Fate and effects of enrofloxacin in aquatic systems under different light conditions[J].Environmental Science&Technology,39(23):9140-9146
Larson R A,Weber E J.1996.Reaction mechanisms in environmental organic chemistry[J].Carbohydrate Polymers,29(3):293-294
Latch D E,Packer J L,Stender B L,et al.2005.Aqueous photochemistry of triclosan:Formation of 2,4-dichlorophenol,2,8-dichlorodibenzo-pdioxin,and oligomerization products[J].Environmental Toxicology and Chemistry,24(3):517-525
Leifer A.1988.The Kinetics of Environmental Aquatic Photochemistry:Theory and Practice[M].Washington,DC:American Chemical Society
Luo Y,Xu L Q,Rysz M,et al.2011.Occurrence and transport of tetracycline,sulfonamide,quinolone,and macrolide antibiotics in the Haihe River Basin,China[J].Environmental Science&Technology,45(5):1827-1833
MatykiewiczováN,KlánováJ,Klán P.2007.Photochemical degradation of PCBs in snow[J].Environmental Science&Technology,41(24):8308-8314
Mill T.1999.Predicting photoreaction rates in surface waters[J].Chemosphere,38(6):1379-1390
Na G,Fang X,Cai Y,et al.2013.Occurrence,distribution,and bioaccumulation of antibiotics in coastal environment of Dalian,China[J].Marine Pollution Bulletin,69(1/2):233-237
Na G S,Gu J,Ge L K,et al.2011.Detection of 36 antibiotics in coastal waters using high performance liquid chromatography-tandem mass spectrometry[J].Chinese Journal of Oceanology and Limnology,29(5):1093-1102
Niu J F,Li Y,Wang W L.2013.Light-source-dependent role of nitrate and humic acid in tetracycline photolysis:Kinetics and mechanism[J].Chemosphere,92(11):1423-1429
Qiang Z,Adams C.2004.Potentiometric determination of acid dissociation constants(p Ka)for human and veterinary antibiotics[J].Water Research,38(12):2874-2890
Vione D,Minella M,Maurino V,et al.2014.Indirect photochemistry in sunlit surface waters:Photoinduced production of reactive transient species[J].Chemistry-A European Journal,20(34):10590-10606
Wei R C,Ge F,Huang S Y,et al.2011.Occurrence of veterinary antibiotics in animal wastewater and surface water around farms in Jiangsu Province,China[J].Chemosphere,82:1408-1414
Wei X X,Chen J W,Xie Q,et al.2013.Distinct photolytic mechanisms and products for different dissociation species of ciprofloxacin[J].Environmental Science&Technology,47(9):4284-4290
Werner J J,Arnold W A,Mc Neill K.2006.Water hardness as a photochemical parameter:Tetracycline photolysis as a function of calcium concentration,magnesium concentration,and p H[J].Environmental Science&Technology,40(23):7236-7241
Xie Q,Chen J W,Zhao H X,et al.2013.Different photolysis kinetics and photooxidation reactivities of neutral and anionic hydroxylated polybrominated diphenyl ethers[J].Chemosphere,90(2):188-194
Xu H,Cooper W J,Jung J,et al.2011.Photosensitized degradation of amoxicillin in natural organic matter isolate solutions[J].Water Research,45(2):632-638
杨常青,王龙星,侯晓虹,等.2012.大辽河水系河水中16种抗生素的污染水平分析[J].色谱,30(8):756-762
Yang X H,Xie H B,Chen J W,et al.2013.Anionic phenolic compounds bind stronger with transthyretin than their neutral forms:Nonnegligible mechanisms in virtual screening of endocrine disrupting chemicals[J].Chemical Research in Toxicology,26(9):1340-1347
张翠,胡学锋,骆永明.2016.模拟太阳光下水中土霉素的光化学降解[J].环境化学,35(3):430-438
Zhang Q Q,Ying G G,Pan C G,et al.2015.A comprehensive evaluation of antibiotics emission and fate in the river basins of china:Sourceanalysis,multimedia modelling,and linkage to bacterial resistance[J].Environmental Science and Technology,49(11):6772-6782
Ziolli R L,Jardim W F.2003.Photochemical transformations of watersoluble fraction(WSF)of crude oil in marine waters:A comparison between photolysis and accelerated degradation with Ti O2using GC-MS and UVF[J].Journal of Photochemistry and Photobiology A:Chemistry,155(1):243-252