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| Titel |
Uptake of 13N-labeled N2O5 to citric acid aerosol particles |
| VerfasserIn |
Goran Grzinic, Thorsten Bartels-Rausch, Mario Birrer, Andreas Türler, Markus Ammann |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250076663
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| Zusammenfassung |
| Dinitrogen pentoxide is a significant reactive intermediate in the night time chemistry of
nitrogen oxides. Depending on atmospheric conditions it can act either as a NO3 radical
reservoir or as a major NOx sink by heterogeneous hydrolysis on aerosol surfaces. As such, it
can influence tropospheric ozone production and therefore the oxidative capacity of the
atmosphere. Furthermore it’s suspected of being a non negligible source of tropospheric Cl,
even over continental areas [1,2].
We used the short-lived radioactive tracer 13N delivered by PSI’s PROTRAC facility [3]
in conjunction with an aerosol flow tube reactor in order to study N2O5 uptake kinetics
on aerosol particles. 13NO is mixed with non labeled NO and O3 in a gas reactor
where N2O5 is synthesized under dry conditions to prevent hydrolysis on the reactor
walls. The resulting N2O5 flow is fed into an aerosol flow tube reactor together
with a humidified aerosol flow. By using movable inlets we can vary the length of
the aerosol flow tube and thus the reaction time. The gas feed from the reactor
is then directed into a narrow parallel plate diffusion denuder system that allows
for selective separation of the gaseous species present in the gas phase. Aerosol
particles are trapped on a particle filter placed at the end of the denuder system. The
activity of 13N labeled species trapped on the denuder plates and in the particle filter
can be monitored via scintillation counters. Aerosol uptake measurements were
performed with citric acid aerosols in a humidity range of 27-61.5% RH. The results
obtained from our measurements have shown that the uptake coefficient increases
with humidity from 1.65±0.3x10-3 (~27% RH) to 1.25±0.3x10-2 (45% RH) and
2.00±0.3x10-2 (61.5% RH). Comparison to literature data shows that this is similar to
values reported for some polycarboxylic acids (like malonic acid), while being higher
than some others [4]. The increase is likely related to the increasing amount of
water associated with citric acid at higher humidity that promotes hydrolysis of
N2O5.
References
1. Chang, W.L., et al., Heterogeneous Atmospheric Chemistry, Ambient Measurements,
and Model Calculations of N(2)O(5): A Review. Aerosol Science and Technology, 2011.
45(6): p. 665-695.
2. Thornton, J.A. et al., A large atomic chlorine source inferred from mid-continental
reactive nitrogen chemistry. Nature, 2010. 464:7286 p. 271-274.
3. Ammann, M., Using 13N as tracer in heterogeneous atmospheric chemistry
experiments. Radiochim. Acta, 2001. 89: p. 831-838.
4. IUPAC Subcommittee on Gas Kinetic Data Evaluation., Data Sheet VI.A3.8 N2O5 +
H2O (aqueous organic aerosols), 2009. |
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