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Atompheric aerosols play an important role in offseting global
warming due totheir scattering solar radiation received by the
earth.In the present study,atmospheric aerosols were collected
at kenting national park from September to October in 1997.An
aerosol collecting system consists of an aerosol spectrometer to
acquire aerosol size distribution,an integrating Nephelometer to
measure aerosol scattering coefficient($sp),a Honeycomb denuder
couple with a cyclone inlet to obtain fine fraction for chemical
compositions was installed at the site.The results show daily
averages of aerosol scattering coefficients of green wavelength
ranged from 0.01 to 0.116km-1.Aerosol scatteriing coefficient
was highly correlated with meterological factors,e.g.,$sp was
enhanced as relative humidity was reached 75~80% and above.
During the sampling period,the weather was shifting from
summertime to prevailing northeast monsoon,which resulted in a
fluctuted wind speed for varying from 1 to 17ms-1.The $sp was
decreased with an increasing wind speed for wind speed less than
8ms-1,however,the trend was opposite as wind speed higher than
8ms-1.An increase of $sp was observed as submicron particles
were increased when an event occured at the nearby environment.
In the study,the average of the collected aerosol mass
concentration is 19.5ugm-3.A moderate inverse correlation
(r=0.55)is found for aerosol mass with wind speed as wind speed
is less than 8ms-1.In contrast,a low correlation(r=0.32)between
aerosol mass and wind speed 1s observed for wind speed higher
than 8ms-1.The chemical analysis shows,aerosols are composed of
37.2% water-soluble ions,22.7% carbonaceous contents,18.4% metal
ions,and 18.1% water mass(a value caluated from Lee and
Hsu,1998).Among chemical species,sulfate ions,nitrate ions,
ammonium ions,and aerosol water mass highly correlated with each
other.A stepwise regression analysis shows correlated with
selected aerosol chemical compositions.Meanwhile,$spis also
found a high correlation with the corresponding value caluated
from Mie theory(Bohern and Huffman,1983). An enhancemant factor
calculation indicates sulfate ions are with non-sea-salt source
as the ratio of SO42-/Na+ is always large than 10.For the source
apportionment of aerosols,a "chlorine loss schene"(Ohta and
Okita,1990)and an Absolute Principle Component Analysis(Thurston
and Spengler,1985)were adopted in this study.The apportioned
reslts from the two methods agreed well with each other except
for minor deviations in soil dusts and ses-salts. During the
sampling period,synoptic weather patterns can be recognized as
four major ones i.e.,Pacific high,prevaiing northeast moonsoon,
before the passage of the cold front.Eight-hour backward
trajeectory(Dharmavarm,1987)shows,a high $sp is usually
associated with the air mass passing through the land and
bringing more secondary aerosols.For weather patterns like
prevailing northeast moonsoon or before the passage of a cold
front,the wind speeds were high,which resulted in a high
fraction of sea-salt in the collected aerosols.In summary,the
$sp at kenting site shows the characteristics of aerosol optical
property in a clean area.From Mie calculation,the $sp is shown
to be dominated by the submicron particles.In the meantime,
either aerosol physical property like particle size distribution
or aerosol chemical compositions is demonstrated to estimated
$sp well.
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