Formation of reactive nitrogen oxides from urban grime photochemistry
Open Access
- 24 May 2016
- journal article
- research article
- Published by Copernicus GmbH in Atmospheric Chemistry and Physics
- Vol. 16 (10), 6355-6363
- https://doi.org/10.5194/acp-16-6355-2016
Abstract
Impervious surfaces are ubiquitous in urban environments and constitute a substrate onto which atmospheric 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 (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.Keywords
Funding Information
- Natural Sciences and Engineering Research Council of Canada (0000300001)
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