How does a 10-fold pulse increase of aircraft-related NO x impact the global burdens of O 3 and secondary organic aerosol (SOA)?

Abstract

Aircraft emissions are an important and growing global source of nitrogen oxides (NO_x ). At cruising altitude, the atmosphere is particularly NO_x -sensitive and aircraft emissions contribute to ozone (O₃) production and oxidation of volatile organic pollutants that ultimately produce secondary organic aerosol (SOA). Rapid growth of the global fleet of aircraft and the number of flights require a careful investigation on the atmospheric impact of potential increases in total aircraft-emitted NO_x . In this study, we simulated atmospheric composition before, during and after two 10× pulses of total aircraft NO_x emissions, one in winter and one in summer of 2007. Results showed that the initial NO_x enhancement (up to 3.25% averaged over the globe) was removed after the first 2 months and the change in O₃ burden increases for 5 months (up to 3.1 and 2.7% averaged over the globe, respectively, for winter and summer perturbations). The NO_x and O₃ enhancements follow previously observed temporal patterns, but SOA showed strong season-specific results. During the summer, the NO_x pulse decreased total secondary organic gases (SOGs) and SOA burdens, suggesting an inverse relationship with enhanced oxidation. During the winter, the NO_x pulse increased the SOG and SOA burdens with SOA lagging SOG. The SOG enhancement has a spatio-temporal pattern similar to NO_x . The highest changes in SOA and SOG burdens of different regions during the summer and winter pulse increases were below 1.6%. However, O₃ pollution with burden increases as high as 8% in the winter months and 6% in the summer months of the northern hemisphere may even represent an air quality concern.

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