Geoscience Reference
In-Depth Information
Formaldehyde is the only major VOC that's readily detected via satellite, says
Gunnar Schade, an assistant professor in atmospheric sciences at Texas A&M Univer-
sity in College Station. Its presence generally signals hydrocarbon sources such as for-
ests, biomass burning, vehicles, and industrial processes that emit formaldehyde pre-
cursors such as ethene, isoprene, and methane. Deciduous forests tend to be the largest
source of formaldehyde detected by satellites, though urban hotspots also show up.
Formaldehyde is short-lived in the atmosphere, but global images show modest
long-distance transport at lower concentrations. The concentrations tracked by satel-
lite “are not a real health concern,” Schoeberl says. However, formaldehyde and other
VOCs do contribute to the formation of ground-level ozone. Although VOCs pose a
variety of known human health risks, it is hard to say whether the concentrations in the
atmosphere that can be tracked by satellite pose those same risks.
The SO
2
is created primarily through combustion processes in power plants and
various industrial processes such as pulp and paper mills. Important natural sources
include volcanoes and biomass burning. Health effects include premature mortality,
multiple respiratory problems, headache, nausea, and thyroid system disruptions.
Like VOCs, SO
2
is diffi cult to track via satellite because of its spectral properties.
Only major events such as volcanic eruptions and concentrated sources such as major
urban areas tend to show up. It is even harder translating atmospheric contamination
into surface levels. “SO
2
on the ground has been a challenge,” Haynes says, although
recent advancements have allowed near-ground retrievals of SO
2
from such major
events.
Signifi cant breakthroughs in satellite instruments or algorithms do not appear to
be on the near horizon. However, SO
2
remains a concern for long-range transport. In
an article by Chulkyu Lee and colleagues in the March 2008 issue of Atmospheric
Environment, a team of Korean and German researchers using satellite data as one
tool concluded that Chinese sources of SO
2
boosted the pollutant at ground level at a
Korean location in May 2005 by up to 7.8 ppb. That's a signifi cant portion of the EPA
annual standard of 30 ppb or the 24-hour standard of 140 ppb.
THE GOLDEN AGE?
Satellite instruments may become increasingly important for tracking long-dis-
tance air pollutant transport, filling in data gaps between monitors, cross-checking
ground-based emissions estimates and measurements, forecasting air quality, pro-
viding advance alerts for health care professionals, and supplying additional infor-
mation for regulators as well as people and organizations trying to meet regulations.
Along with information on air pollutants, satellite information is also being used
to help with other important environmental health concerns, such as the spread of
infectious diseases (as reflected by changes in vegetation and temperature, which
can influence disease vector populations), dust, heat, land use changes, and climate
change.
