Recent Results of Individual Asian Dust Particle Analysis

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Recent Results of Individual Asian Dust Particle
Analysis
Daizhou Zhang Prefectural University of
Kumamoto, Japan Yasunobu Iwasaka, et al. Nagoya
University, Japan Guangyu Shi, et al. Institute
of Atmospheric Physics, Chinese Academy of
Science, China
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Our observation sites
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1. At the source region (Dunhuang) Results by
balloon observation
A dust layer at 35 km over the desert areas in
summer 2002 when no dust events were reported or
recorded.
Source was not identified and there isnt further
information about the layer except some LIDAR
observation.
The layer was confirmed by the onboard particle
counter and LIDAR observations.
A similar layer was found in another balloon
mission on March 24, 2003 (spring).
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2. Over the Sea of Japan (Wakasa Bay) Results
by aircraft observation
A dust layer was found above 4 km over the Sea of
Japan by two flight missions in July 2000 and
July 2001 when no dust events were reported or
recorded.
The layer was confirmed by the onboard particle
counter and LIDAR observations.
The particles were likely from the arid areas of
China and Mongolia.
Is this layer related to the layer observed at
Dunhuang?
Does it mean the constant summer contribution of
mineral to the ocean?
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3. At a coastal site of China (Qingdao)
Results by surface observation
Anthropogenic mineral particles In the
pre-frontal air, high concentration of mineral
particles were observed. Most of them contained
anthropogenic pollutants such as sulfur. They
were from East China.
Asian dust particles Mineral particles in the
post-frontal air rarely contained pollutants such
as sulfur. They were from the arid areas in West
China and were the so-called Asian dust particles.
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3. At a coastal site of China (Qingdao)
Results by surface observation
In the investigation of the chemical composition
of Asian dust particles in the continental
atmosphere, the pre- and post-frontal mineral
particles should be considered separately. In
particular, we must be careful when using results
of the analysis of integrated filter samples.
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4. At southwest Japan (Kumamoto) Results by
surface observation
Comparisons to results at Qingdao
More than 60 of dust particles mixed with sea
salt during their dispersion from China to Japan.
The distributions showed similar patterns with
peaks around 3 ?m while the dominant particles
were absolutely different.
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4. At southwest Japan (Kumamoto)
Distributions segregated by the mixture levels of
mineral and sea salt.
The distribution patterns were independent from
mixture levels.
Dust particle size increased due to the
combination with sea salt.
Where were the particles whose diameter became
larger than 3mm? ? Most of them must have been
removed, otherwise the distributions should have
shifted to larger ranges.
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4. At southwest Japan (Kumamoto)
Our suggestions for the interpretation of the
distribution consistence of dust storm particles
at different sites along the transport routes.
The size distributions of dust storm particles
observed at downstream areas should not be
conserved by the original dust particles. They
should be the results of growth of smaller
particles and removal of larger particles.
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5 At southwestern Japan (Kumamoto) on Cl loss
from sea salt
Dust particles modify the chlorine chemistry in
marine atmosphere through adsorbing HCl and
restraint of HCl release from sea salt components
in mixture particles. Cl deposition onto dust
particles is not ignorant compared to S
deposition in marine atmosphere.
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Summary
1. There were dust layers in the free troposphere
over East Asia in summer.
2. At the coastal area of China, Asian dust
particles were in the post-frontal air and rarely
contained anthropogenic pollutants. The
pollutants were found on anthropogenic mineral
particles in the pre-frontal air.
3. The size distributions of dust storm particles
observed at downstream areas should be the
results of growth of smaller particles and
removal of larger particles.
4. Dust particles modify the chlorine chemistry
in marine atmosphere through adsorbing HCl and
restraint of HCl release from sea salt components
in mixture particles.