The NO2-O3 system at sub-ppm concentrations: Influence of temperature and relative humidity

The stoichiometry and kinetics of the reaction of NO₂ with O₃ at sub-ppm concentration level have been investigated as a function of temperature and relative humidity. The experiments were performed in a continuous flow reactor using chemiluminescent and wet chemical methods of analysis.The rate constant found can be described by the Arrhenius expression: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaiikaiaaik% dacaGGUaGaaGyoaiaaiEdacqGHXcqScaaIWaGaaiOlaiaaigdacaaI% 0aGaaiykaiabgEna0kaaigdacaaIWaWaaWbaaSqabeaacqGHsislca% aIXaGaaG4maaaakiaabwgacaqG4bGaaeiCaiaacIcadaWcgaqaaiaa% cIcacqGHsislcaaIYaGaaGOnaiaaikdacaaIWaGaeyySaeRaaGyoai% aaicdacaGGPaaabaGaamivaiaacMcacaqGGaGaae4yaiaab2gadaah% aaWcbeqaaiaabodaaaGccaqGGaWaaSGbaeaacaqGTbGaae4BaiaabY% gacaqGLbGaae4yaiaabwhacaqGSbGaaeyzamaaCaaaleqabaGaaeyl% aiaabgdaaaaakeaacaqGZbWaaWbaaSqabeaacaqGTaGaaeymaaaaaa% aaaaaa!62A3![(2.97 pm 0.14) times 10^{ - 13} {text{exp}}({{( - 2620 pm 90)} mathord{left/ {vphantom {{( - 2620 pm 90)} {T){text{ cm}}^{text{3}} {text{ }}{{{text{molecule}}^{{text{ - 1}}} } mathord{left/ {vphantom {{{text{molecule}}^{{text{ - 1}}} } {{text{s}}^{{text{ - 1}}} }}} right. kern-nulldelimiterspace} {{text{s}}^{{text{ - 1}}} }}}}} right. kern-nulldelimiterspace} {T){text{ cm}}^{text{3}} {text{ }}{{{text{molecule}}^{{text{ - 1}}} } mathord{left/ {vphantom {{{text{molecule}}^{{text{ - 1}}} } {{text{s}}^{{text{ - 1}}} }}} right. kern-nulldelimiterspace} {{text{s}}^{{text{ - 1}}} }}}}] and are independent of the relative humidity. As commonly encountered in previous studies a lower-than-two reaction stoichiometry is observed.Heterogeneous reactions occurring at the reactor wall seem to be essential in the reaction mechanism. The NO₃ wall conversion to NO₂ and the N₂O₅ wall scavenging in the presence of H₂O are suggested to account for the observed stoichiometric factors.