Heterogeneous conversion of NO2 and NO on HNO3 treated soot surfaces: atmospheric implications
Item
Title (Dublin Core)
Heterogeneous conversion of NO2 and NO on HNO3 treated soot surfaces: atmospheric implications
Description (Dublin Core)
In the present study, the heterogeneous conversion of nitrogen oxide (NO) and nitrogen dioxide (NO<sub>2</sub>) was studied at atmospheric humidity levels on flame soot surfaces treated with gaseous nitric acid (HNO<sub>3</sub>). In addition, the heterogeneous reaction of HNO<sub>3</sub> on soot was investigated at atmospheric humidity. <P style="line-height: 20px;"> For the treatment of soot by pure HNO<sub>3</sub> only reversible uptake with a surface coverage of ~1-2x10<sup>14</sup> HNO<sub>3</sub> cm<sup>-2</sup> was observed for HNO<sub>3</sub> mixing ratios in the range 250-800ppbv. Only for higher HNO<sub>3</sub> mixing ratios of >800ppbv the formation of NO and NO<sub>2</sub> was observed. The results were not affected by the addition of NO. In none of the experiments with HNO<sub>3</sub> the formation of nitrous acid (HONO) was observed. For HNO<sub>3</sub> mixing ratios <600ppbv the upper limit yields for HONO, NO<sub>2</sub> and NO were found to be <0.2%, <0.5% and <1%, respectively. Compared to untreated soot, the product formation of the reaction of NO<sub>2</sub> with soot was not significantly affected when the soot surface was treated with gaseous HNO<sub>3</sub> prior to the experiment. Only for high surface coverage of HNO<sub>3</sub> the formation of HONO was suppressed in the initial phase of the reaction, probably caused by the blocking of active sites by adsorbed HNO<sub>3</sub>. <P style="line-height: 20px;"> Under the assumption that the experimental findings for the used model flame soot can be extrapolated to atmospheric soot particles, the results show that the reactions of HNO<sub>3</sub> and HNO<sub>3</sub>+NO on soot surfaces are unimportant for a "renoxification" of the atmosphere and do not represent an atmospheric HONO source. In addition, the integrated HONO yield of ca. 10<sup>14</sup>cm<sup>-2</sup> in the reaction of NO<sub>2</sub> with soot is not significantly influenced by simulated atmospheric processing of the soot surface by HNO<sub>3</sub>, and is still too small to explain HONO formation in the atmosphere.
Creator (Dublin Core)
Kleffmann, J.
Wiesen, P.
Date (Dublin Core)
2018-06-28
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-5-77-2005
https://acp.copernicus.org/articles/5/77/2005/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
