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nitrate concentration (Fig. 4(b)) resembles that of NO
x
and VOC emissions
(Fig. 2). Nitrogen formation on the aerosol is small and more effective in
the regions where both VOC and NO
x
emissions are large, indicating the
importance of photochemistry. Also, the maximum ammonium concentra-
tion (Fig. 4(c)) occurs in southeast China where the maximum ammonia
emission occurs (Fig. 2).
The spatial distribution of monthly mean column PM
10
concentration
(Fig. 4(d)) shows that the high PM
10
concentrations in northern China
and Mongolia are mainly due to the Asian dust aerosol whereas those in
eastern China and Korea are a mixture of the Asian dust and anthropogenic
aerosols.
4.3.
Contribution of each type of aerosol to the total
aerosol mass
The fractional contributions of each type of aerosol to the time-area aver-
aged column integrated total mass of aerosols in the whole analysis period
of the whole domain (Fig. 1) are shown in Fig. 5. The time-area mean
column aerosol mass is about 160 mg/m
2
of which 79 and 21% contribute
to Asian dust and other aerosols, respectively (Fig. 5(a)).
In March 2002 in Asia, several severe dust storms occurred, so that the
contribution of Asian dust to the total aerosol mass was much larger than
that of the other aerosols. Averaged total nonsoil oriented aerosol mass is
35 mg/m
2
, of which 23, 24, 16, 11, 5, and 21% contributed to the PM
10
Fig. 5. The fractional contributions of each type of aerosol to the time-area averaged
column integrated (a) total aerosol mass and (b) anthropogenic aerosol mass in the whole
analysis domain in Fig. 1 for the period from 1 to 31 March 2002.
