Characteristics and global
warming/cooling effects
of atmospheric aerosols
M. Kasahara*, R. Höller, S. Tohno
and Y. Ohnishi
Graduate
School of Energy Science, Kyoto University,
Uji,
Kyoto 611-0011, Japan
Tel:
(81 77) 438 4408 Fax: (81 77) 438 4411 Email : kasahara@energy.kyoto-u.ac.jp
ABSTRACT
Last one decade, the importance of global environmental
problems such as global warming and acid rain has been recognized at the
worldwide. Atmospheric aerosols play an important role in such global
environmental problems as well as the local air pollution problem. The grasp
of physical and chemical properties of aerosol particles is essential to make
clear the behavior of aerosols in the atmosphere and also their effects on
human health and atmospheric environment.
In this paper, the
characteristics of atmospheric aerosols and the effects of aerosols on the
atmospheric environment, especially on global warming/cooling effect, are
discussed.
Characteristics
and environmental effects of
atmospheric
aerosols
The properties of aerosol
particles are described by a number of physical and chemical factors such as
particle size, concentration, chemical component, density, optical property,
reactivity, etc. And the most important factors are generally the concentration,
particle size and chemical composition. The physical and chemical properties of
atmospheric aerosols depend on their sources and scavenging mechanisms.
After
aerosol particles are emitted from various kinds of natural and anthropogenic
sources, they are transported by wind and dispersed. The properties of aerosols
are changed by physical and chemical reactions during the transportation.
Gas-to-particle conversion including the cloud formation is very important
processes in aerosol behavior. The cloud formation is closely related to the
global warming/cooling and acid rain problems.
Characterization of atmospheric
aerosols
In order
to characterize the atmospheric aerosols, the atmospheric aerosols were
collected using a Low Pressure Cascade impactor. The LPC impactor can classify
the particles between about 0.01 and 30 micrometer into 13 size ranges. The
elemental concentrations of collected particles were measured by the PIXE
analysis. Figure 1 shows the typical size distribution of the total mass, S and
Fe elements. The thin solid line, thin broken line and thick solid line mean
the insoluble component, soluble component and sum of them, respectively. The
particle size distribution was grouped into three types. The first type shown
typically in S, Zn and Pb size distribution skewed to the smaller size range
and had only one peak in the fine particle region. The second type shown in Si,
Ca, Fe and Ti skewed to the larger size range and had nearly one peak in the
coarse particle region. The third type was the bimodal distribution with one
peak each in fine and coarse fractions and the distributions of the total mass,
K, V, Mn and Cu were represented by this type.
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Figure 1. Particle size distribution of total mass, S and
Fe: Thin solid line = insoluble component;
Thin broken line = soluble component; and Thick solid line = total.
Global warming/cooling effects
of atmospheric aerosols
The
atmospheric aerosols influence on global warming in two ways. One is direct
effect by absorbing and scattering the radiation. The other is indirect effect
through the cloud formation. The effects of aerosols on the global warming/cooling
depend on their physical and chemical properties, especially the amount of
elemental carbon (EC).
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Acknowledgements
A part of this work has been done under the program of
the Research for the Future (RFTF) of the Japan Society for the Promotion of
Science (JSPS- RFTF97P01002) and Grant-in-Aid
for Scientific Research (B) under Grant No. 09044161 from Ministry of Education,
Science, Sports and Culture, Japan.
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