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Global Particulate
(PM) Air Pollution and its Effects on California
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| Particulate Air Pollution: |
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The global atmospheric particle
load comes from a mix of natural and human sources. Dust from Earth's great deserts mixes with dust from
roads, farms, and other soil disturbance. Smoke from wildfires mixes with smoke from burning forests and
grasslands as well as coal and oil.
Particle sulfate forms from atmospheric
chemical conversion of sulfur gases to particles; the sulfur gases come from natural sources, such as volcanoes
and plankton in the oceans, as well as from sulfur contamination in fossil fuels.
Global dust sources are dominated
by Earth's great deserts, as shown in Fig. 2 below.
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Figure 2.
Major dust source areas based on TOMS Satellite Aerosol Index data (NASA). Arrow marks Taklamakan Desert
in western China.
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Carbon monoxide is accompanied by
other combustion-related pollutants, such as smoke, soot, sulfates, and toxic materials. Present global levels
of population, urban and industrial development, and vegetation burning are causing rising concentrations of air
pollution to be spread throughout the Northern Hemisphere.
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| Asian Dust: |
| Sheltered from the Asian monsoon by the "wall"
of the Himalayan Plateau, The desert " belt " of northern China is so dry that dust wells up from the
land even without strong winds, creating a " fog " called the buran. |
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Figure 3. Satellite
composite maps of the continental U.S. (top) and China (bottom) at the same scale. The great desert belt
of northern China is shown in red, the mountain region of the Himalayan Plateau in blue.
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Figure 4. Space shuttle image
of Taklamakan Desert (upper left) and Himalayan Plateau (bottom). Mountains are clear, but desert basin is obscured
by dust.
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Major
spring storms passing over the Chinese deserts can raise enormous
clouds of dust that are then pushed into eastern China and across the
Pacific. These clouds are called " yellow sand " storms (huangsha
in China, kosa in Japan). Figure 5 shows a natural color satellite
image of such a dust storm.
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Figure 5. A storm
pushes Chinese dust across the Yellow sea to Korea and Japan (bottom right) in April, 2001 (CNES).
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Figure 6. Pedestrians shelter
from "yellow sand" in Beijing.
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| Asian Pollution Crosses
the Pacific: |
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In April, 1998, a very large Asian
dust storm hit North America, spreading a dust haze across much of the U.S. and Canada, and providing a natural
experiment that California scientists used to analyze the impact of Asian dust on North America.
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Figure 7 below
shows the dust cloud and some of the measurement sites used to analyze it.
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Analysis of the April 1998
dust gave scientists a chemical signature for the dust, which was used to analyze historical air samples.
This lead to the discovery that dilute Asian dust, accompanied by combustion products, is present most of the time
at elevated sites in North America.
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| Papers by ARB staff on the
subject of Global Particulate
(PM) Air Pollution and its Effects on California are listed below: |
VanCuren, R. A., S. S. Cliff, K. D. Perry, and M. Jimenez-Cruz
(2005), Asian continental aerosol persistence above the marine boundary layer over the eastern North Pacific: Continuous
aerosol measurements from Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2), /J. Geophys.
Res/., *110*, D09S90, doi:10.1029/2004JD004973.
(PDF
- 1,258 KB) |
VanCuren, R. A., Asian aerosols in North America: Extracting
the chemical composition and mass concentration of the Asian continental aerosol plume from long-term aerosol records
in the western United States,/ J. Geophys. Res./, *108*(D20), doi:10.1029/2003JD003459, 2003.
(PDF
- 1,060 KB) |
VanCuren, R. A., Cahill, T. A., Asian aerosols in North
America: Frequency and concentration of fine dust, /J. Geophys. Res./ *107*(D24), doi:10.1029/2002JD002204, 2002.
(PDF
- 913 KB) |
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