Abstract
Abstract. Heterogeneous uptake of dinitrogen pentoxide (N2O5) and production of nitryl chloride (ClNO2) are important nocturnal atmospheric processes that have significant implications for the production of secondary pollutants. However, the understanding of N2O5 uptake processes and ClNO2 production remains limited, especially in China. This study presents a field investigation of the N2O5 heterogeneous uptake coefficient (γ(N2O5)) and ClNO2 production yield (ϕ) in a polluted area of northern China during the summer of 2014. The N2O5 uptake coefficient and ClNO2 yield were estimated by using the simultaneously measured ClNO2 and total nitrate in 10 selected cases, which have concurrent increases in the ClNO2 and nitrate concentrations and relatively stable environmental conditions. The determined γ(N2O5) and ϕ values varied greatly, with an average of 0.022 for γ(N2O5) (±0.012, standard deviation) and 0.34 for ϕ (±0.28, standard deviation). The variations in γ(N2O5) could not be fully explained by the previously derived parameterizations of N2O5 uptake that consider nitrate, chloride, and the organic coating. Heterogeneous uptake of N2O5 was found to have a strong positive dependence on the relative humidity and aerosol water content. This result suggests that the heterogeneous uptake of N2O5 in Wangdu is governed mainly by the amount of water in the aerosol, and is strongly water limited, which is different from most of the field observations in the US and Europe. The ClNO2 yield estimated from the parameterization was also overestimated comparing to that derived from the observation. The observation-derived ϕ showed a decreasing trend with an increasing ratio of acetonitrile to carbon monoxide, an indicator of biomass burning emissions, which suggests a possible suppressive effect on the production yield of ClNO2 in the plumes influenced by biomass burning in this region. The findings of this study illustrate the need to improve our understanding and to parameterize the key factors for γ(N2O5) and ϕ to accurately assess photochemical and haze pollution.
Highlights
The nocturnal heterogeneous reaction of dinitrogen pentoxide (N2O5) with aerosols is a loss pathway of NOx and a source of aerosol nitrate and gas-phase nitryl chloride (ClNO2) (Brown et al, 2006; Osthoff et al, 2008; Thornton et al, 2010; Sarwar et al, 2014) and thereby has important implications for air quality (e.g., Li et al, 2016; Tang et al, 2017)
The low N2O5 value is consistent with the short steady-state lifetime of N2O5 (τ (N2O5)) for the study period, ranging from 0.1 to 10 min, suggesting that the direct loss of N2O5 via heterogeneous reaction and/or indirect loss of N2O5 via decomposition to NO3 were rapid in this region
We present an in-depth analysis of the N2O5 uptake coefficient and ClNO2 yield in a polluted northern China environment during the summer of 2014
Summary
The nocturnal heterogeneous reaction of dinitrogen pentoxide (N2O5) with aerosols is a loss pathway of NOx and a source of aerosol nitrate and gas-phase nitryl chloride (ClNO2) (Brown et al, 2006; Osthoff et al, 2008; Thornton et al, 2010; Sarwar et al, 2014) and thereby has important implications for air quality (e.g., Li et al, 2016; Tang et al, 2017). Tham et al.: Heterogeneous N2O5 uptake and ClNO2 yield in polluted northern China phase nitrate radical (NO3) after sunset via the oxidation of nitrogen dioxide (NO2) by O3 and further reaction of NO3 with another NO2, yielding N2O5. The accommodation of N2O5 on the aqueous surface of the aerosol (Reaction R1) and reaction with liquid water (H2O) leads to the formation of a protonated nitric acid intermediate (H2ONO+2 ) and a nitrate (NO−3 ) (Reaction R2; Thornton and Abbatt, 2005; Bertram and Thornton, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
