 |
| Titel |
The effect of local sources on the isotopic composition of nitrous oxide in the tropical free troposphere and tropopause layer |
| VerfasserIn |
P. L. Croteau, K. A. Boering, E. L. Atlas, S. M. Schauffler, D. R. Blake |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024945
|
|
|
|
|
|
| Zusammenfassung |
| We present measurements and analysis of the complete isotopic composition of
nitrous oxide (δ15Nbulk, δ15Nα, δ15Nβ, and δ18O) in whole-air samples collected
in the tropical free troposphere and the tropical tropopause layer (TTL) aboard
the NASA DC-8 and WB-57 aircraft as part of the Costa Rica Aura Validation
Experiment (CRAVE) and Tropical Composition Cloud and Climate Coupling (TC4)
campaigns in 2006 and 2007, respectively. The measurements show that for δ18O the
vertical profile has structure throughout the troposphere, implying a significant
local influence. Using a modified Keeling plot approach, we determine that the
isotopic composition of the local source during the 08 August 2007 DC-8 flight
from the TC4 campaign is more consistent with an ocean source than with a soil
source. Further evidence of the influence of the ocean on the isotopic composition
of N2O in the tropical troposphere is obtained through tracer-tracer plots of the
isotopic composition, especially δ18O, with common tracers of marine influence
that were measured in the whole-air samples. We further demonstrate that there
is a strong and significant anti-correlation between the isotopic composition and
ethane in samples influenced by an industrial plume. This set of measurements
demonstrates that useful measurements of the variability of the isotopic composition of
tropospheric N2O are possible at currently attainable precision and that this variability is
a useful tool in investigating the sources of this important greenhouse gas. This
suggests that a large scale measurement campaign of N2O isotopic composition
would be useful in constraining the N2O budget and its biogeochemical cycling. |
|
|
|
|
|
|