title: Photodegradation of 2,4-D induced by NO₂(-) in aqueous solutions: the role of NO₂.
abstract: To elucidate the effect of nitrite ion (NO₂(-)) on the photodegradation of organic pollutants, a 300 W mercury lamp and Pyrex tubes restricting the transmission of wavelengths below 290 nm were used to simulate sunlight, and the photodegradation processes of 2,4-dichlorophenoxyacetic acid (2,4-D) with different concentrations of NO₂(-) in freshwater and seawater were studied. The effect of reactive oxygen species (ROS) on the photolysis of 2,4-D was also demonstrated using electron paramagnetic resonance (EPR). The results indicated that the 2,4-D photolysis reaction followed the first-order kinetics in freshwater and seawater under different concentrations of NO₂(-). Meanwhile, the photochemical reaction rate of 2,4-D increased with increasing concentration of NO₂(-). When the concentration of NO₂(-) was lower than 23 mg/L, the photodegradation rate of 2,4-D in seawater was higher than that in freshwater. However, when the concentration of NO₂(-) was reached 230 mg/L, 2,4-D degradation slowed down in seawater. It was important to note that EPR spectra showed NO₂ radical was generated in the NO₂(-) solution under simulated sunlight irradiation, indicating that 2,4-D photodegradation could be induced by NO₂. These results show the key role of NO₂(-) in photochemistry and are helpful for better understanding of the phototransformation of environmental contaminants in natural aquatic systems.
authors: National Marine Environmental Monitoring Center, Dalian 116023, China. Electronic address: cyyu@nmemc.gov.cn.
authors: Chunyan
authors: C
authors: Yu
authors: School of Fisheries and Life Science, Dalian Ocean University, Dalian 116023, China.
authors: Hua
authors: H
authors: Wang
authors: School of Fisheries and Life Science, Dalian Ocean University, Dalian 116023, China.
authors: Xuan
authors: X
authors: Liu
authors: Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China. Electronic address: quanxie@dlut.edu.cn.
authors: Xie
authors: X
authors: Quan
authors: Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors: Shuo
authors: S
authors: Chen
authors: Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors: Jianlin
authors: J
authors: Zhang
authors: National Marine Environmental Monitoring Center, Dalian 116023, China.
authors: Peng
authors: P
authors: Zhang
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005618:Fresh Water; D009573:Nitrites / Q000737:chemistry*; D010782:Photolysis; D017382:Reactive Oxygen Species / Q000737:chemistry; D012623:Seawater; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013472:Sunlight
chemical_list: D009573:Nitrites; D017382:Reactive Oxygen Species; D012996:Solutions; D015084:2,4-Dichlorophenoxyacetic Acid
keywords: 2,4-Dichlorophenoxyacetic acid (2,4-D); NO(2)(); Nitrite ion; Photodegradation