Roughly half the aerosols that affect air quality and climate change in North America may be coming from other continents, including Asia, Africa and Europe, according to a new study. Researchers at the University of Maryland, College Park, NASA Goddard Space Flight Center, University of Maryland at Baltimore County and the Universities Space Research Association reported the findings a recent issue of Science.
Atmospheric particles can travel
thousands of miles downwind and impact the environment in other regions, found
lead researcher Hongbin Yu of the University of Maryland, and his team. This
could offset emission controls in North America and suggests there are more
factors affecting domestic pollution than the Environmental Protection Agency
has accounted for.
"People have been concerned about
how an emerging Asian economy and increased manmade pollution will influence
North American air quality and climate, but we found that dust makes large
contributions here," says Yu, an associate research scientist in UMD's
Earth System Science Interdisciplinary Center (ESSIC). "So we cannot just
focus on pollution. We need to consider dust."
The study, which provides the first
satellite-measurement-based estimate of the amount of airborne particles that
come to North America from overseas, shows this migrating dust usually comes in
at high altitudes and in the United States is most likely to affect upper
Most of the pollution migrating into the
North American atmosphere is not industrial emissions but dust from Asia,
Africa and the Middle East, Yu found. Out of the total annual accumulation of
foreign aerosols, 87.5 percent is dust from across the Pacific, 6.25 percent is
comprised of combustion aerosols from the same region and 6.25 percent is
Saharan dust from across the Atlantic.
The researchers say the EPA is aware that
foreign pollution affects U.S. air, but it is unclear on the amount of imported
aerosols, Yu says. The study revealed that much of the dust migration occurs at
high altitudes and is unlikely to affect the air we breathe.
Current satellite sensor technology
allows scientists to track aerosol plumes across the ocean and measure their
composition and particle characteristics. The 3-D satellite measurements can
distinguish dust from other types of aerosols such as those released from
burning biomass and fuel. While dust and combustion aerosol migration occurs
year round, it is heightened in the spring due to strong seasonal wind patterns
and extra-tropical cyclones.
UMD climate scientist Antonio (Tony)
Busalacchi, who is chairman of the Joint Scientific Committee for the World
Climate Research Programme and chairman of the Board on Atmospheric Sciences
and Climate of the U.S. National Academy of Sciences/National Research Council,
says one of the most interesting points Yu and his coauthors make in their
study is that even a reduction of industrial emissions by the emerging
economies of Asia could be overwhelmed by an increase in dust emissions due to
changes in meteorological conditions and potential desertification.
Half of the Particulate Pollution in North America Comes from Other Continents
September 19, 2012