On July 6, 2011, the US Environmental Protection Agency finalized the rule that
protects the health of millions of Americans by helping states reduce air pollution
and attain clean air standards. This rule, known as the Cross-State Air Pollution Rule
(CSAPR), requires states to significantly improve air quality by reducing power
plant emissions that contribute to ozone and/or fine particle pollution in other states
[60]. In a separate, but related, regulatory action, US EPA finalized a supplemental
rulemaking on December 15, 2011 to require five states – Iowa, Michigan, Missouri,
Oklahoma, and Wisconsin – to make summertime NO X reductions under the
CSAPR ozone season control program. CSAPR requires a total of 28 states to reduce
annual SO 2 emissions, annual NO X emissions, and/or ozone season NO X emissions
to assist in attaining the 1997 ozone and fine particle and 2006 fine particle National
Ambient Air Quality Standards (NAAQS).
8.3 Causes of Acid Rain
Two elements, sulfur and nitrogen, are primarily responsible for the harmful effects
of acid rain. Sulfur is found as a trace element in coal and oil. When these are burned
in power plants (see Fig. 7.13) and industrial boilers, the sulfur combines with
oxygen to form sulfur dioxide (SO 2 ). Because SO 2 does not react with most
chemicals found in the atmosphere, it can travel long distances. Eventually, if it
comes in contact with ozone or hydrogen peroxide, it can be converted to sulfur
trioxide. Sulfur trioxide can dissolve in water, forming a dilute solution of sulfuric
acid. In the gas phase sulfur dioxide is oxidized by reaction with the hydroxyl radical
via an intermolecular reaction:
SO 2 þ OH • ! HOSO 2 •
which is followed by:
HOSO 2 • þ O 2 ! HO 2 • þ SO 3
In the presence of water, sulfur trioxide (SO 3 ) is converted rapidly to sulfuric
acid:
SO 3 gas
ð ÞþH 2 O liquid
ð
Þ!H 2 SO 4 aqueous
ð
Þ
Nitrogen makes up about 78% of the atmosphere. When heated to the temperatures found in steam boilers and internal combustion engines, it can combine with
oxygen from the atmosphere to form nitrogen oxide and nitrogen dioxide (NO x ).
NO x is the sum of nitrogen oxide and nitrogen dioxide in a given parcel of air. These
can dissolve in water, forming weak solutions of nitric and nitrous acids. Nitrogen
dioxide reacts with OH to form nitric acid:
7 Lake Restoration
287
protects the health of millions of Americans by helping states reduce air pollution
and attain clean air standards. This rule, known as the Cross-State Air Pollution Rule
(CSAPR), requires states to significantly improve air quality by reducing power
plant emissions that contribute to ozone and/or fine particle pollution in other states
[60]. In a separate, but related, regulatory action, US EPA finalized a supplemental
rulemaking on December 15, 2011 to require five states – Iowa, Michigan, Missouri,
Oklahoma, and Wisconsin – to make summertime NO X reductions under the
CSAPR ozone season control program. CSAPR requires a total of 28 states to reduce
annual SO 2 emissions, annual NO X emissions, and/or ozone season NO X emissions
to assist in attaining the 1997 ozone and fine particle and 2006 fine particle National
Ambient Air Quality Standards (NAAQS).
8.3 Causes of Acid Rain
Two elements, sulfur and nitrogen, are primarily responsible for the harmful effects
of acid rain. Sulfur is found as a trace element in coal and oil. When these are burned
in power plants (see Fig. 7.13) and industrial boilers, the sulfur combines with
oxygen to form sulfur dioxide (SO 2 ). Because SO 2 does not react with most
chemicals found in the atmosphere, it can travel long distances. Eventually, if it
comes in contact with ozone or hydrogen peroxide, it can be converted to sulfur
trioxide. Sulfur trioxide can dissolve in water, forming a dilute solution of sulfuric
acid. In the gas phase sulfur dioxide is oxidized by reaction with the hydroxyl radical
via an intermolecular reaction:
SO 2 þ OH • ! HOSO 2 •
which is followed by:
HOSO 2 • þ O 2 ! HO 2 • þ SO 3
In the presence of water, sulfur trioxide (SO 3 ) is converted rapidly to sulfuric
acid:
SO 3 gas
ð ÞþH 2 O liquid
ð
Þ!H 2 SO 4 aqueous
ð
Þ
Nitrogen makes up about 78% of the atmosphere. When heated to the temperatures found in steam boilers and internal combustion engines, it can combine with
oxygen from the atmosphere to form nitrogen oxide and nitrogen dioxide (NO x ).
NO x is the sum of nitrogen oxide and nitrogen dioxide in a given parcel of air. These
can dissolve in water, forming weak solutions of nitric and nitrous acids. Nitrogen
dioxide reacts with OH to form nitric acid:
7 Lake Restoration
287