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| Titel |
Quantifying atmospheric nitrate formation pathways based on a global model of the oxygen isotopic composition (Δ¹⁷O) of atmospheric nitrate |
| VerfasserIn |
B. Alexander, M. G. Hastings, D. J. Allman, J. Dachs, J. A. Thornton, S. A. Kunasek |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 14 ; Nr. 9, no. 14 (2009-07-28), S.5043-5056 |
| Datensatznummer |
250007531
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| Publikation (Nr.) |
 copernicus.org/acp-9-5043-2009.pdf |
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| Zusammenfassung |
| The oxygen isotopic composition (Δ17O) of atmospheric nitrate
is a function of the relative abundance of atmospheric oxidants (O3,
ROx=OH+HO2+RO2) and the formation pathway of nitrate
from its precursor NOx (=NO+NO2). Coupled observations and
modeling of nitrate Δ17O can be used to quantify the relative
importance of chemical formation pathways leading to nitrate formation and
reduce uncertainties in the budget of reactive nitrogen chemistry in the
atmosphere. We present the first global model of atmospheric nitrate Δ17O and compare with available observations. The largest uncertainty
for calculations of nitrate Δ17O is the unconstrained
variability in the Δ17O value of tropospheric ozone. The model
shows the best agreement with a global compilation of observations when
assuming a Δ17O value of tropospheric ozone equal to 35‰ and
preferential oxidation of NOx by the terminal oxygen atoms of ozone.
Calculated values of annual-mean nitrate Δ17O in the lowest
model layer (0–200 m above the surface) vary from 7‰ in the tropics to
41‰
in the polar-regions. The global, annual-mean tropospheric inorganic nitrate
burden is dominated by nitrate formation via NO2+OH (76%),
followed by N2O5 hydrolysis (18%) and NO3+DMS/HC
(4%). Calculated nitrate Δ17O is sensitive to the relative
importance of each nitrate formation pathway, suggesting that observations
of nitrate Δ17O can be used to quantify the importance of
individual reactions (e.g. N2O5 hydrolysis) leading to nitrate
formation if the Δ17O value of ozone is known. |
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