NO_3 radicals accumulate during the night, thereby being the most critical night oxidant. Owing to the low concentration and dramatic variation, the detection of atmospheric NO_3 radicals is still challenging. In this...NO_3 radicals accumulate during the night, thereby being the most critical night oxidant. Owing to the low concentration and dramatic variation, the detection of atmospheric NO_3 radicals is still challenging. In this paper, an LED-based Long Path Differential Optical Absorption Spectroscopy（LPDOAS） instrument is developed for measuring the atmospheric NO_3 radicals. This instrument is composed of a Schmidt-Cassegrain telescope, a combined emitting and receiving fiber,and a red LED equipped with a thermostat, and has a center wavelength of 660 nm, covering the NO_3 strongest absorption peak（662 nm）. The influence of LED temperature fluctuations is discussed. The temperature of the LED lamp with a home-made thermostat is tested, showing a stability of ±0.1℃. The principle and fitting analyses of LED-LPDOAS are presented. A retrieval example and a time series of NO_3 radical concentrations with good continuity for one night are shown. The detection limit of NO_3 for 2.6-km optical path is about 10 ppt.展开更多
Rate coefficients for the reaction of N03 radicals with 6 unsaturated volatile organic compounds(VOCs) in a 7300 L simulation chamber at ambient temperature and pressure have been determined by the relative rate metho...Rate coefficients for the reaction of N03 radicals with 6 unsaturated volatile organic compounds(VOCs) in a 7300 L simulation chamber at ambient temperature and pressure have been determined by the relative rate method.The resulting rate coefficients were determined for isoprene,2-carene,3-carene,methyl vinyl ketone(MVK),methacrolein(MACR)and crotonaldehyde(CA),as(6.6±0.8)×10-13,(1.8±0.6)×10-11,(8.7±0.5)×10-12,(1.24±1.04)×10-16,(3.3±0.9)×10-15 and(5.7±1.2)×10-15 cm3/(molecule·sec),respectively.The experiments indicate that NO3 radical reactions with all the studied unsaturated VOGs proceed through addition to the olefinic bond,however,it indicates that the introduction of a carbonyl group into unsaturated VOGs can deactivate the neighboring olefinic bond towards reaction with the NO3 radical,which is to be expected since the presence of these electronwithdrawing substituents will reduce the electron density in the π orbitals of the alkenes,and will therefore reduce the rate coefficient of these electrophilic addition reactions.In addition,we investigated the product formation from the reactions of 2-carene and 3-carene with the NO3 radical.Qualitative identification of an epoxide(C10H16OH+),caronaldehyde(C10H16O2 H+) and nitrooxy-ketone(C10H16O4 NH+) was achieved using a proton transfer reaction time-of-flight mass spectrometer(PTR-TOF-MS) and a reaction mechanism is proposed.展开更多
基金Project supported by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(Grant Nos.XDB05040200 and XDB05010500)
文摘NO_3 radicals accumulate during the night, thereby being the most critical night oxidant. Owing to the low concentration and dramatic variation, the detection of atmospheric NO_3 radicals is still challenging. In this paper, an LED-based Long Path Differential Optical Absorption Spectroscopy（LPDOAS） instrument is developed for measuring the atmospheric NO_3 radicals. This instrument is composed of a Schmidt-Cassegrain telescope, a combined emitting and receiving fiber,and a red LED equipped with a thermostat, and has a center wavelength of 660 nm, covering the NO_3 strongest absorption peak（662 nm）. The influence of LED temperature fluctuations is discussed. The temperature of the LED lamp with a home-made thermostat is tested, showing a stability of ±0.1℃. The principle and fitting analyses of LED-LPDOAS are presented. A retrieval example and a time series of NO_3 radical concentrations with good continuity for one night are shown. The detection limit of NO_3 for 2.6-km optical path is about 10 ppt.
基金supported by Labex Voltaire(No.ANR-10-LABX100-01)the French National Research Agency(Agence Nationale de la Recherche)and the Research Grants Council(ANR-RGC)program(project ANR-16-CE01-0013)+2 种基金ARD PIVOTS program(Ambition Recherche Développement Plateformes d’Innovation,de Valorisation,d’Optimisation,Technologiques environnmentale S,supported by the centre-Val de Loire regional council)funding from the European Union’s Horizon 2020 research and innovation program through the EUROCHAMP-2020 Infrastructure Activity(No.730997)the Marie Sk?odowska Curie Actions Programme(No.690958)(MARSU)
文摘Rate coefficients for the reaction of N03 radicals with 6 unsaturated volatile organic compounds(VOCs) in a 7300 L simulation chamber at ambient temperature and pressure have been determined by the relative rate method.The resulting rate coefficients were determined for isoprene,2-carene,3-carene,methyl vinyl ketone(MVK),methacrolein(MACR)and crotonaldehyde(CA),as(6.6±0.8)×10-13,(1.8±0.6)×10-11,(8.7±0.5)×10-12,(1.24±1.04)×10-16,(3.3±0.9)×10-15 and(5.7±1.2)×10-15 cm3/(molecule·sec),respectively.The experiments indicate that NO3 radical reactions with all the studied unsaturated VOGs proceed through addition to the olefinic bond,however,it indicates that the introduction of a carbonyl group into unsaturated VOGs can deactivate the neighboring olefinic bond towards reaction with the NO3 radical,which is to be expected since the presence of these electronwithdrawing substituents will reduce the electron density in the π orbitals of the alkenes,and will therefore reduce the rate coefficient of these electrophilic addition reactions.In addition,we investigated the product formation from the reactions of 2-carene and 3-carene with the NO3 radical.Qualitative identification of an epoxide(C10H16OH+),caronaldehyde(C10H16O2 H+) and nitrooxy-ketone(C10H16O4 NH+) was achieved using a proton transfer reaction time-of-flight mass spectrometer(PTR-TOF-MS) and a reaction mechanism is proposed.
