 |
| Titel |
The effect of organic aerosol material on aerosol reactivity towards ozone |
| VerfasserIn |
Anneke Batenburg, Cassandra Gaston, Joel Thornton, Annele Virtanen |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102228
|
| Publikation (Nr.) |
 EGU/EGU2015-1535.pdf |
|
|
|
|
|
| Zusammenfassung |
| After aerosol particles are formed or emitted into the atmosphere, heterogeneous
reactions with gaseous oxidants cause them to “age”. Aging can change aerosol
properties, such as the hygroscopicity, which is an important parameter in how the
particles scatter radiation and form clouds. Conversely, heterogeneous reactions on
aerosol particles play a significant role in the cycles of various atmospheric trace
gases.
Organic compounds, a large part of the total global aerosol matter, can exist in
liquid or amorphous (semi)solid physical phases. Different groups have shown
that reactions with ozone (O3) can be limited by bulk diffusion in organic aerosol,
particularly in viscous, (semi)solid materials, and that organic coatings alter the surface
interactions between gas and aerosol particles. We aim to better understand and
quantify how the viscosity and phase of organic aerosol matter affect gas-particle
interactions.
We have chosen the reaction of O3 with particles composed of a potassium iodide (KI)
core and a variable organic coating as a model system. The reaction is studied in an aerosol
flow reactor that consists of a laminar flow tube and a movable, axial injector for the injection
of O3. The aerosol-containing air is inserted at the tube’s top. The interaction length (and
therefore time), between the particles and the O3 can be varied by moving the injector.
Alternatively, the production of aerosol particles can be modulated. The remaining O3
concentration is monitored from the bottom of the tube and particle concentrations are
measured simultaneously, which allows us to calculate the reactive uptake coefficient
γ.
We performed exploratory experiments with internally mixed KI and polyethylene glycol
(PEG) particles at the University of Washington (UW) in a setup with a residence time
around 50 s. Aerosol particles were generated in an atomizer from solutions with varying
concentrations of KI and PEG and inserted into the flow tube after they were diluted
and humidified and excess flow was ventilated. It proved necessary to separate the
particles before the O3 monitor to prevent interference with the optical O3 detection
method. Unfortunately, large O3 losses occurred on the used filter, which limited the
accuracy of the γ-determinations. Nevertheless, it was found that already a small
amount of added PEG considerably reduced the observed γ. Other aerosol separation
methods are currently being investigated for the follow-up experiments in Kuopio. |
|
|
|
|
|
|