Field Measurement of Alkyl Nitrates in the Atmosphere
Alkyl nitrates(ANs),chemicals with the formula RONO2,are important oxidation products during the reaction between atmospheric nitrogen oxides(NOx)and volatile organic compounds(VOCs).The generation of ANs removes NOx from the atmosphere,and inhibits atmospheric oxidation by terminating the HOx cycle.Some ANs are easily taken up by particulate,as important precursors of secondary organic aerosols,thereby affecting atmospheric air quality and global cli-mate change.Atmospheric model simulations and field campaigns have shown that ANs are important for local complex pollution and nitrogen cycling.However,as ANs are widely distributed in the atmosphere,with a wide variety and active chemical properties,it makes the field measurements of ANs very scarce due to the lack of measurement methods and stand-ard substances.In this study,firstly,the atmospheric chemical mechanism focused on ANs is introduced,and then the meas-urement techniques for single species and total ANs are summarized,which mainly include gas chromatography electron capture(GC-ECD),mass spectrometry(MS),thermal dissociation laser-induced fluorescence(TD-LIF)and absorption spec-trometry.Overall,mass spectrometry is an important development direction for single-species measurement methods of ANs,while absorption spectroscopy is an emerging total measurement method with great development potential.Field measure-ments of ANs were carried out mainly in Europe and the United States.However,the atmospheric environment of high NOx and high anthropogenic VOCs in China is different from that of low NOx and high biogenic VOCs in Europe and the United States,and thus there are differences in the atmospheric distributions of ANs,which introduces challenge for field measure-ments of ANs.Finally,the distribution characteristics of ANs in the environments of ocean,forest,city,and free atmosphere in the troposphere are summarized,and an outlook on the difficulties and development trends of ANs chemistry at present is given,which will provide a reference for the development of the measurement technology and the research on the chemical mechanism of ANs in China.
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