 |
| Titel |
Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O3, NO2, and H2O on soot coated with benzo[a]pyrene |
| VerfasserIn |
M. Springmann, D. A. Knopf, N. Riemer |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 19 ; Nr. 9, no. 19 (2009-10-07), S.7461-7479 |
| Datensatznummer |
250007672
|
| Publikation (Nr.) |
 copernicus.org/acp-9-7461-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| This study assesses in detail the effects of heterogeneous chemistry
on the particle surface and gas-phase composition by modeling the
reversible co-adsorption of O3, NO2, and H2O on soot coated
with benzo[a]pyrene (BaP) for an urban plume scenario over a period
of five days. By coupling the Pöschl-Rudich-Ammann (PRA) kinetic
framework for aerosols (Pöschl et al., 2007) to a box
model version of the gas phase mechanism RADM2, we are able to track
individual concentrations of gas-phase and surface species over the
course of several days. The flux-based PRA formulation takes into
account changes in the uptake kinetics due to changes in the
chemical gas-phase and particle surface compositions. This dynamic
uptake coefficient approach is employed for the first time in a
broader atmospheric context of an urban plume scenario. Our model scenarios include one to three adsorbents and
three to five coupled surface reactions. The results show a
variation of the O3 and NO2 uptake coefficients of more than
five orders of magnitude over the course of the simulation time and a
decrease in the uptake coefficients in the various scenarios by more
than three orders of magnitude within the first six hours.
Thereafter, periodic peaks of the uptake coefficients follow the
diurnal cycle of gas-phase O3-NOx reactions. Physisorption of
water vapor reduces the half-life of the coating substance BaP
by up to a factor of seven by permanently occupying ~75% of
the soot surface. Soot emissions modeled by replenishing
reactive surface sites lead to maximum gas-phase O3 depletions of
41 ppbv and 7.8 ppbv for an hourly and six-hourly replenishment
cycle, respectively. This conceptual study highlights the
interdependence of co-adsorbing species and their non-linear
gas-phase feedback. It yields further insight into the
atmospheric importance of the chemical oxidation of particles and
emphasizes the necessity to implement detailed heterogeneous
kinetics in future modeling studies. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|