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

Our observation sites

Dunhuang

Qingdao Wakasa Bay

Kumamoto

The Pacific Ocean

CHINA

MONGOLIA

1. At the source region (Dunhuang) Results by balloon observation

Dunhuang

The Pacific Ocean

CHINAA dust layer at 3~5 km over the desert areas in summer 2002 when no dust events were reported or recorded.

A similar layer was found in another balloon mission on March 24, 2003 (spring).

The layer was confirmed by the onboard particle counter and LIDAR observations.

Rel

ativ

e w

eig

ht r

atio

Particle analyzed

Source was not identified and there isn’t further information about the layer except some LIDAR observation.

The Pacific Ocean

CHINA

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.

Does it mean the constant summer contribution of mineral to the ocean?

Is this layer related to the layer observed at Dunhuang?

The Pacific Ocean

CHINA

MONGOLIA

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.

Status of dust plumes and polluted air refer to the cold front at the coastal area during the dust storm event

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.

The Pacific Ocean

CHINA

MONGOLIA

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.

Status of dust plumes and polluted air refer to the cold front at the coastal area during the dust storm event

4. At southwest Japan (Kumamoto) Results by surface observation

The Pacific Ocean

CHINA

MONGOLIA

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100

Q-1 (236) Q-2 (161) Q-3 (168) K-1 (761) K-2 (751) K-3 (798)

Num

ber frac

tion

(%)

Mixture particles Neat dust particles

Mixture of dust particles and sea salt at Qingdao(Q) Kumamoto(K)

・ More than 60% of dust particles mixed with sea salt during their dispersion from China to Japan.

Comparisons to results at Qingdao:

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40

60

80

100

0 2 4 6 8 10

Diameter(m)

dN/d

logD

Neat dustMixture

0

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60

80

100

0 2 4 6 8 10

Diameter(m)

dN/d

logD

Neat dustMixture

Number-size distribution of dust particles at Qingdao(a) and Kumamoto(b)

(a) (b)

・ The distributions showed similar patterns with peaks around 3 m while the dominant particles were absolutely different.

4. At southwest Japan (Kumamoto)

The Pacific Ocean

CHINA

MONGOLIA

・ Dust particle size increased due to the combination with sea salt.

Where were the particles whose diameter became larger than 3m? Most of them must have been removed, otherwise the

distributions should have shifted to larger ranges.

0

10

20

30

40

50

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0 1 2 3 4 5 6 7 8 9 10

Diameter(m)

dN/d

logD

Neat dustMineral>>SeasaltMineral Seasalt～Mineral<<SeasaltSeasalt

K-2

Distributions segregated by the mixture levels of mineral and sea salt.

・ The distribution patterns were independent from mixture levels.

Asian Continent PacificSea Japan

Dust Plume

Seasalt Seasalt

Dust Plume Dust Plume

Most Particles of diameter>3～4m by Gravitational Settling

Most Particles are <3m

Most Particles are <3m

GROWTHby combination

with Seasalt

Neat Dust

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.

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.

Chlorine chemistry associated with sea salt in marine atmospherewhen dust particles appear

NaClSea saltparticle

SO2, NOx, etc

Deposition

HCl

Reaction

Dust particle

Re-deposition

or

Mixing particle

Deposition

SO2, NOx, etc

HCl

Reaction

HCl scavenged

HCl release restrained

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.