| Autor: |
Baergen AM; Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6., Styler SA; Atmospheric Chemistry Department (ACD), Leibniz-Institut für Troposphärenforschung (TROPOS) , Permoserstrasse 15, 04318 Leipzig, Saxony, Germany., van Pinxteren D; Atmospheric Chemistry Department (ACD), Leibniz-Institut für Troposphärenforschung (TROPOS) , Permoserstrasse 15, 04318 Leipzig, Saxony, Germany., Müller K; Atmospheric Chemistry Department (ACD), Leibniz-Institut für Troposphärenforschung (TROPOS) , Permoserstrasse 15, 04318 Leipzig, Saxony, Germany., Herrmann H; Atmospheric Chemistry Department (ACD), Leibniz-Institut für Troposphärenforschung (TROPOS) , Permoserstrasse 15, 04318 Leipzig, Saxony, Germany., Donaldson DJ; Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.; Department of Physical and Environmental Sciences, University of Toronto Scarborough , 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada. |
| Abstrakt: |
Deposition of atmospheric constituents--either gas phase or particulate--onto urban impervious surfaces gives rise to a thin "urban grime" film. The area exposed by these impervious surfaces in a typical urban environment is comparable to, or greater than, that of particles present in the urban boundary layer; however, it is largely overlooked as a site for heterogeneous reactions. Here we present the results of a field campaign to determine and compare the chemical composition of urban grime and of particles collected simultaneously during the autumn of 2014 at an urban site in central Leipzig, Germany. We see dramatically reduced ammonium and nitrate levels in the film as compared to particles, suggesting a significant loss of ammonium nitrate, thus enhancing the mobility of these species in the environment. Nitrate levels are 10% lower for films exposed to sunlight compared to those that were shielded from direct sun, indicating a possible mechanism for recycling nitrate anion to reactive nitrogen species. Finally, chloride levels in the film suggest that urban grime could represent an unrecognized source of continental chloride available for ClNO2 production even in times of low particulate chloride. Such source and recycling processes could prove to be important to local and regional air quality. |
