Chemistry of Urban Grime: Inorganic Ion Composition of Grime vs Particles in Leipzig, Germany

Abstract

Always cite the published version, so the author(s) will receive recognition through services that track citation counts, e.g. Scopus. If you need to cite the page number of the author manuscript from TSpace because you cannot access the published version, then cite the TSpace version in addition to the published version using the permanent URI (handle) found on the record page. Deposition of atmospheric constituents -either gas phase or particulate -onto urban 16 impervious surfaces gives rise to a thin "urban grime" film. The area exposed by these 17 impervious surfaces in a typical urban environment is comparable to, or greater than, that 18 of particles present in the urban boundary layer, however it is largely overlooked as a site 19 for heterogeneous reactions. Here we present the results of a field campaign to determine 20 and compare the chemical composition of urban grime and of particles collected 21 simultaneously during the autumn of 2014 at an urban site in central Leipzig, Germany. 22We see dramatically reduced ammonium and nitrate levels in the film as compared to 23 particles suggesting a significant loss of ammonium nitrate, thus enhancing the mobility 24 of these species in the environment. Nitrate levels are 10% lower for films exposed to 25 sunlight compared to those that were shielded from direct sun, indicating a possible 26 mechanism for recycling nitrate anion to reactive nitrogen species. Finally, chloride 27 levels in the film suggest that it could represent an unrecognized source of continental 28 chloride available for ClNO 2 production even in times of low particulate chloride. Such 29 source and recycling processes could prove to be important to local and regional air 30 quality. 31

Formation of reactive nitrogen oxides from urban grime photochemistry

“…The concentrations of HONO and NO 2 were calculated using the method described by Fiedler and Gherman (Fiedler et al, 2003;Gherman et al, 2008) and previously used by us (Reeser et al, 2013). This uses measured mirror reflectivity (Washenfelder et al, 2008), Rayleigh cross sections of the carrier gas (Bodhaine et al, 2010) and the absorption cross sections of NO 2 (Vandaele et al, 1998) and HONO (Stutz et al, 2000) to fit the experimental spectra with DOASIS software (Lehmann, 2009). DOASIS uses a linear least-squares method to fit the absorption bands to reference spectra and a polynomial to fit broad features such as those from Rayleigh scattering, Mie scattering and temperature drifts.…”

HONO emission and production determined from airborne measurements over the Southeast U.S.

“…Although atmospheric HONO has been measured for several decades [ Perner and Platt , ], sources of HONO to the atmosphere remain uncertain [e.g., Stutz et al ., ; Kleffmann , ; Zhou et al ., ; Li et al ., ; VandenBoer et al ., ; Gall et al ., ]. HONO sources include direct emission from combustion [ Kirchstetter et al ., ; Kurtenbach et al ., ; Stutz et al ., ; Wood et al ., ; Jurkat et al ., ; Burling et al ., ] and soils [ Oswald et al ., ], formation by gas phase reaction of OH and NO [ Calvert et al ., ], and production by surface reaction of nitrogen‐containing compounds [e.g., Stutz et al ., ; Stemmler et al ., ; Kleffmann , ; Zhou et al ., ; VandenBoer et al ., ; Baergen et al ., ]. During the day, rapid photolysis (11 min lifetime for solar zenith angle < 20°) [ Stockwell and Calvert , ] limits HONO mixing ratios.…”

Introductory lecture: atmospheric chemistry in the Anthropocene

“…This is consistent with the much higher than expected photolysis rates of surface-bound nitrate species in "urban grime". [240][241][242] For example, while one might expect the surface HNO 3 to be dissociated in the presence of water, there is evidence that a large fraction is actually in the form of nitric acid hydrates and even the nitric acid dimer. 243 There is also indirect evidence for a rich and reactive surface-bound "soup" of different species in concentrated nitric acid, 243,244 which might bear some similarity to the surface-bound acid concentrated in urban surface lms.…”

“…585 In addition, ab initio molecular dynamics simulations show that for water lms on surfaces, N 2 O 5 can be stabilized at the air-water interface in such a way that reaction with Cl À via an S N 2 reaction can occur. 588 Baergen et al 242 proposed that similar chemistry could occur in "urban grime" which contains both oxides of nitrogen and chloride ions, as well as a complex mixture of organics.…”