Formation of Reactive Nitrogen Oxides from Urban Grime Photochemistry
نویسندگان
چکیده
Impervious surfaces are ubiquitous in urban environments and constitute a substrate onto which atmospheric 10 constituents can deposit and undergo photochemical and oxidative processing, giving rise to “urban grime” films. HNO3 and N2O5 are important sinks for NOx in the lower atmosphere and may be deposited onto these films, forming nitrate through surface hydrolysis. Although such deposition has been considered as a net loss of NOx from the atmosphere, there is increasing evidence that surface-associated nitrate undergoes further reaction. Here, we examine the gas phase products of the photochemistry of real, field-collected urban grime using incoherent broadband cavity enhanced absorption spectroscopy 15 (IBBCEAS). Gas phase nitrogen oxides are emitted upon illumination of grime samples and their production increases with ambient relative humidity (RH) up to 35% after which the production becomes independent of RH. These results are discussed in the context of water uptake onto and evaporation from grime films.
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Interactive comment on “Formation of Reactive Nitrogen Oxides from Urban Grime
It is believed that the deposition of NOy (mainly HNO3, even if N2O5 is also discussed here) is a sink process for NOx, however this study challenges this point of view and demonstrates, for the time, that photochemistry of photochemistry of urban grime is as a potential source of gaseous nitrous acid (HONO). This has been suggested before but never demonstrated. This study therefore a nice pie...
متن کاملInteractive comment on “Formation of Reactive Nitrogen Oxides from Urban Grime Photochemistry” by A. M. Baergen and D. J. Donaldson
Manuscript by Alyson Baergen and D. J. Donaldson focuses on formation of HONO, a key chemical species and/or reaction intermediate in atmospheric chemistry, during photolysis of urban grime. Given the fact that sources and formation of daytime HONO in urban setup are poorly understood, this study reveals potential chemical and photochemical reaction pathways and mechanisms to yield HONO. The kn...
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