Particulate Air Pollution and its Effects on California
This page last reviewed January 20, 2017
Particulate Air Pollution
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.
Figure 2. Major dust source areas based on TOMS Satellite Aerosol Index data (NASA). Arrow marks Taklamakan Desert in western China.
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.
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.
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.
Figure 4. Space shuttle image of Taklamakan Desert (upper left) and Himalayan Plateau (bottom). Mountains are clear, but desert basin is obscured by dust.
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 (huangshain China, kosa in Japan). Figure 5 shows a natural color satellite image of such a dust storm.
Figure 5. A storm pushes Chinese dust across the Yellow sea to Korea and Japan (bottom right) in April, 2001 (CNES).
Figure 6. Pedestrians shelter from "yellow sand" in Beijing.
Asian Pollution Crosses the Pacific
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.
Figure 7 below shows the dust cloud and some of the measurement sites used to analyze it.
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.
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)
For more information about air pollution research, please contact Heather Choi at (916) 322-3893.