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| Titel |
Emission of nitrous acid from soil and biological soil crusts as a major source of atmospheric HONO on Cyprus |
| VerfasserIn |
Hannah Meusel, Alexandra Tamm, Dianming Wu, Uwe Kuhn, Anna-Lena Leifke, Bettina Weber, Hang Su, Jos Lelieveld  , Thorsten Hoffmann, Ulrich Pöschl, Yafang Cheng |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140220
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| Publikation (Nr.) |
 EGU/EGU2017-3576.pdf |
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| Zusammenfassung |
| Elucidation of the sources and atmospheric chemistry of nitrous acid (HONO) is highly
relevant, as HONO is an important precursor of OH radicals. Up to 30% of the OH budget are
formed by photolysis of HONO, whereas major fractions of HONO measured in the field
derive from yet unidentified sources. Heterogeneous conversion of nitrogen dioxide (NO2) to
HONO on a variety of surfaces (soot, humic acid aerosol) is assumed to be a major HONO
source (Stemmler et al., 2007, Ammann et al., 1998). In rural regions, however, NO2
concentrations were found to be too low to explain observed HONO concentrations,
as e.g., in the case of a recent field study on the Mediterranean island of Cyprus
(Meusel et al., 2016). In this study a good correlation between missing sources of
HONO and nitrogen oxide (NO) was found indicating a common origin of both
reactive nitrogen compounds. Simultaneous emission of HONO and NO from soil was
reported earlier (Oswald et al., 2013), and enhanced emission rates were found
when soil was covered by biological soil crusts in arid and semi-arid ecosystems
(Weber et al., 2015). In the present study we measured HONO and NO emissions of
43 soil and soil crust samples from Cyprus during full wetting and drying cycles
under controlled laboratory conditions by means of a dynamic chamber system.
The observed range of HONO and NO emissions was in agreement with earlier
studies, but unlike the study of Weber et al. (2015), we found highest emission
from bare soil, followed by soil covered by light and dark cyanobacteria-dominated
biological soil crusts. Emission rates correlated well with the nitrite and nitrate
contents of soil and biological soil crust samples, and higher nutrient contents of
bare soil samples, as compared to the previous biological soil crust study, explain
the higher bare soil emissions. Integrating the emission rates of bare soil and the
different types of biological soil crusts, based on their local relative abundance, the
calculated total community flux of NO was found to be by far too low to explain the
NO missing source observed during the Cyprus field campaign. For HONO, the
calculated community flux was in good agreement with the mean of the missing
HONO source found during the field study in Cyprus, indicating that soil and the
biological soil crust communities represent a dominant source in remote or rural
areas.
Ammann, M. et al.: Heterogeneous production of nitrous acid on soot in polluted air
masses, Nature, 395, 157-160, 1998.
Meusel, H. et al.: Daytime formation of nitrous acid at a coastal remote site in Cyprus
indicating a common ground source of atmospheric HONO and NO, Atmos. Chem. Phys.,
16, 14475-14493, 2016.
Oswald, R. et al.: HONO Emissions from Soil Bacteria as a Major Source of Atmospheric
Reactive Nitrogen, Science, 341, 1233-1235, 2013.
Stemmler, K. et al.: Light induced conversion of nitrogen dioxide into nitrous acid on
submicron humic acid aerosol, Atmos. Chem. Phys., 7, 4237-4248, 2007.
Weber, B. et al.: Biological soil crusts accelerate the nitrogen cycle through large NO and
HONO emissions in drylands, Proceedings of the National Academy of Sciences of the
United States of America, 112, 15384-15389, 2015. |
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