Geoscience Reference
In-Depth Information
complexes are concentrated. The nss-SO
2
4
can be formed by heterogeneous
oxidation reaction on the aerosol surface.
10
,
11
Observational data support sulfate and nitrate formation on the min-
eral aerosols.
12
-
15
The important mechanism of the aerosol transformation
seems to be the aging processes of naturally emitted aerosols in East Asia
during long range transport.
16
-
18
Through the aerosol aging process volatile
inorganic compounds such as carbonate or bicarbonate in the dust aerosol in
the source region are substituted by particulate sulfate and nitrate, result-
ing in elevated sulfate and nitrate concentration on the dust aerosols.
Since the Asian dust aerosols have rich trace metal components of Al,
Ca,Fe,Na,K,andMg
16
,
19
these components have a strong alkaline nature
and can act as natural neutralizers of the acid species
20
under certain atmo-
spheric conditions. This process is likely to elevate the levels of sulfate and
nitrate on the aerosol.
The purpose of this study is to examine the spatial distributions of Asian
Dust and anthropogenic aerosol concentrations over Asia for the period
from 1 to 31 March 2002.
2. Model Description
2.1.
Aerosol dynamic model
An aerosol dynamic model developed by Chang and Park
21
with the gas-
phase chemistry of the California Institute of Technology (CIT) model
and the aqueous-phase chemistry of the Regional Acid Deposition Model
(RADM) together with meteorological output of the MM5 model on a
60
60 km
2
grid has been used to estimate anthropogenic aerosols and
gaseous pollutants in Asia for the period March 1-31, 2002 (Fig. 1).
The aerosol dynamic model includes such processes as nucleation, con-
densation/evaporation, coagulation, sedimentation, hygroscopic growth,
dry, and wet deposition processes. The detailed model description is given
in Ref. 21.
×
2.2.
Asian dust aerosol model
The Asian Dust Aerosol Model (ADAM) developed by Park and In
6
and
modified by spectral dust emission flux in the source regions
7
has been
used to calculate the temporal and spatial distributions of the Asian Dust
concentration in the model domain. The detailed model description is given
in Refs. 6 and 7.
