Effect of Water Vapor Absorption on Measurements of Atmospheric Nitrate Radical by LP-DOAS |
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Authors: | Su-wen Li Wen-qing Liu Pin-hua Xie Yi-jun Yang De-bao Chen a Zheng Li a |
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Affiliation: | Department of Physics, Huaibei Coal Industry Teachers College, Huaibei 235000, China;Key Laboratory of Environmental Optical and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;Key Laboratory of Environmental Optical and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;Department of Physics, Huaibei Coal Industry Teachers College, Huaibei 235000, China;Department of Physics, Huaibei Coal Industry Teachers College, Huaibei 235000, China;Department of Physics, Huaibei Coal Industry Teachers College, Huaibei 235000, China |
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Abstract: | During the measurement of atmospheric nitrate radical by long-path differential optical absorption spectroscopy, water vapor strong absorption could affect the measurement of nitrate radical and detection limits of system. Under the tropospheric condition, the optical density of water vapor absorption is non-linearly dependent on column density. An effective method was developed to eliminate the effect of water vapor absorption. Reference spectra of water vapor based on the daytime atmospheric absorption spectra, when fitted together with change of cross section with water vapor column densities, gave a more accurate fitting of water vapor absorptions, thus its effect on the measurements of nitrate radical could be restricted to a minimum and detection limits of system reached 3.6 ppt. The modified method was applied during an intensive field campaign in the Pearl River Delta, China. The NO3 concentration in polluted air masses varied from 3.6 ppt to 82.5 ppt with an average level of 23.6±1.8 ppt. |
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Keywords: | Nitrate radical Water vapor absorption Long-path differential optical absorption spectroscopy Detection limit |
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