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Indexed by:Journal Papers

Date of Publication:2014-07-01

Journal:JOURNAL OF ENVIRONMENTAL SCIENCES

Included Journals:ISTIC、SCIE、EI

Volume:26

Issue:7

Page Number:1383-1387

ISSN No.:1001-0742

Key Words:Nitrite ion; Photodegradation; 2,4-Dichlorophenoxyacetic acid (2,4-D); NO2 center dot

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 center dot radical was generated in the NO2- solution under simulated sunlight irradiation, indicating that 2,4-D photodegradation could be induced by NO2 center dot. 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. (C) 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.