on four emissions
Over the next decade, power plant operators will face new requirements to
make substantial reductions in emissions of sulfur dioxide (SO2 ) and
nitrogen oxides (NOx ) beyond the levels called for in the Clean Air Act
Amendments of 1999.
They could also face requirements to reduce carbon dioxide (CO2 ) and
mercury emissions. Several proposed bills in Congress have targeted
reductions of these four emissions. At present, neither the future reduction
requirement nor the complete timetable is known for any of these airborne
emissions, which makes planning for compliance difficult.
Sulfur dioxide belongs to the family of sulfur oxide gases. These gases
are formed when fuel containing sulfur (mainly coal and oil) is burned and
during metal smelting and other industrial processes.
The highest monitored concentrations of SO2 are recorded in the vicinity
of large industrial facilities. Fuel combustion, accounts for most of the
total SO2 emissions.
SO2 emissions decreased 31 percent from 1981 to 2000 and 24 percent from
1991 – 2000.Reductions in SO2 concentrations and emissions since 1994
are due, in large part, to controls implemented under EPA ’s Acid Rain
Program beginning in 1995.
Nitrogen dioxide (NO2 )is a reddish brown, highly reactive gas that is
formed in the ambient air through the oxidation of nitric oxide (NO).
Nitrogen oxides (NOx), the term used to describe the sum of NO, NO2 and
other oxides of nitrogen, play a major role in the formation of ozone,
particulate matter, haze and acid rain.
The major sources of man-made NOx emissions are high-temperature
combustion processes, such as those occurring in automobiles and power
plants. Home heaters and gas stoves also produce substantial amounts of
NO2 in indoor settings.
(From the DOE website. For full text click
Mercury exists in trace
amounts in coal, waste and other materials. When these materials burn,
mercury gases are released into the air. The amount of mercury being
deposited today on land and in water is much lower than in recent
decades. Mercury deposition, at its highest in the 1950s, fell by more
than half by the 1980s.
continued to fall in the decade of the 1990s. In 1993, U.S. yearly
emissions totaled about 242 tons. By the end of the decade, emissions had
declined to less than 160 tons per year. About 50 tons of mercury
emissions come from power plants, about 1/3 of the total.
Carbon dioxide (CO2) is a colorless, odorless gas that humans breath out
and plants breath in during respiration. Although carbon dioxide emissions
are not harmful to health, they have a warming effect on the atmosphere.
This warming, along with a natural rise in temperature is referred to as "global warming." Carbon dioxide, methane,
particulate matter (especially black carbon or soot), nitrous oxide,
fluorinated compounds, and ozone, are some of the compounds contributing
to global warming. Carbon dioxide emissions are largely due to the
combustion of fossil fuels in electric power generation, motor vehicles,