reacts with water to form acids either while airborne or after dry deposition.
On a regional scale, farther downwind from
emission sources, wet deposition is the major acid
deposition mechanism and has earned acid deposition the popular name “acid rain,” though dry
deposition makes substantial contributions to ecosystem acidification [46]. Acid deposition reduces
ecosystem Acid Neutralizing Capacity (ANC)
[47], making future influxes of acids more difficult
to cope with. It also has deleterious effects on soils,
vegetation, and aquatic ecosystems.
Leaching of soil nutrients is a major impact of
acid deposition. Acids deposited in soil react
with the soil’s base cations (largely Ca
2+ but
also Mg
2+ and K
+ ) and increase their mobility
in soils, causing them to leach out of soils and
making them unavailable for plant uptake
[47]. Base cations can be the limiting factor in
forest development and their loss has been identified as the source of decline in many forests
[48]. Increased acidity in soils also negatively
impacts the microbial community in the soil, on
which plant life depends, notably decreasing biological nitrogen fixation rates [49]. Acid deposition stresses plant root systems and leaves [50]
and can leach nutrients (Ca, Mg, and K) from
leaves just as it does from soils [51]. Acid and/or
nitrogen deposition have also been seen to
increase risk of winter injury in Red Spruce
[52]. Acid deposition lowers the pH of lakes
and streams, negatively affecting organisms at
all levels of the aquatic biosphere in terms of
production and growth in lakes with low natural
ANC [53]. Acute mortality and reproductive failure has been a result among fish and some species
have even been lost entirely [53].
Governments in North America and Europe
have addressed acid deposition by limiting the
use of sulfur-rich fuels and introducing technologies to reduce emissions of chemicals that eventually result in acid deposition. Acid deposition
has been substantially reduced as a result of these
strategies, though many of its effects persist.
China has not yet addressed acid rain to the extent
that North American and European governments
have, and today almost 30% of China’s area suffers from acid rain [54]. Given the transboundary
nature of acid deposition, it is likely that much
more area is threatened.
Damage to the Biosphere In addition to the
damages to forests and wildlife caused by acid
deposition, there are other damages caused by
other forms of air pollution. Grantz et al. [55]
provides Guderian’s categories of effects of air
pollutants on ecosystems:
• Accumulation of pollutants in plants and other
ecosystem components (e.g., soil, water)
• Damage to humans as a result of pollutant
accumulation
• Shifts in competition causing changes in species diversity
• Disruption of biogeochemical cycles
• Disruption of stability and reduction in selfregulation capabilities
• Breakdown of stands and associations
• Expansion of denuded zones
Many of these types of impacts have been
observed and linked to particular pollutants. For
example, mercury has been shown to be toxic to
microorganisms, plants, and animals [56], and toxicity of other heavy metals such as lead has also been
confirmed [19]. By binding to proteins, mercury can
also accumulate in organisms and ecosystems [21].
Ground-level ozone (O 3 ) is a known hazard,
leading to reduced production of fine roots in
some trees [57], reduced tree growth [58], and
damage to a plant’s photosynthetic systems
[59]. The reduced activity of plant life as a result
of ozone will reduce an ecosystem’s ability to
store carbon and thereby exacerbates climate
change [60]. Damage and reduced yields of plants
will reduce the availability of food for wild animals, stressing those populations as well.
Visibility
Air Pollution (mostly particles) can reduce visibility. Severe visibility problems arising from
poor air quality have recently been experienced
in some Chinese cities [61]. Human enjoyment of
the environment is impeded by poor visibility and
in extreme cases poor visibility poses a safety
hazard in aviation.
Air Pollution Monitoring and Sustainability
393
On a regional scale, farther downwind from
emission sources, wet deposition is the major acid
deposition mechanism and has earned acid deposition the popular name “acid rain,” though dry
deposition makes substantial contributions to ecosystem acidification [46]. Acid deposition reduces
ecosystem Acid Neutralizing Capacity (ANC)
[47], making future influxes of acids more difficult
to cope with. It also has deleterious effects on soils,
vegetation, and aquatic ecosystems.
Leaching of soil nutrients is a major impact of
acid deposition. Acids deposited in soil react
with the soil’s base cations (largely Ca
2+ but
also Mg
2+ and K
+ ) and increase their mobility
in soils, causing them to leach out of soils and
making them unavailable for plant uptake
[47]. Base cations can be the limiting factor in
forest development and their loss has been identified as the source of decline in many forests
[48]. Increased acidity in soils also negatively
impacts the microbial community in the soil, on
which plant life depends, notably decreasing biological nitrogen fixation rates [49]. Acid deposition stresses plant root systems and leaves [50]
and can leach nutrients (Ca, Mg, and K) from
leaves just as it does from soils [51]. Acid and/or
nitrogen deposition have also been seen to
increase risk of winter injury in Red Spruce
[52]. Acid deposition lowers the pH of lakes
and streams, negatively affecting organisms at
all levels of the aquatic biosphere in terms of
production and growth in lakes with low natural
ANC [53]. Acute mortality and reproductive failure has been a result among fish and some species
have even been lost entirely [53].
Governments in North America and Europe
have addressed acid deposition by limiting the
use of sulfur-rich fuels and introducing technologies to reduce emissions of chemicals that eventually result in acid deposition. Acid deposition
has been substantially reduced as a result of these
strategies, though many of its effects persist.
China has not yet addressed acid rain to the extent
that North American and European governments
have, and today almost 30% of China’s area suffers from acid rain [54]. Given the transboundary
nature of acid deposition, it is likely that much
more area is threatened.
Damage to the Biosphere In addition to the
damages to forests and wildlife caused by acid
deposition, there are other damages caused by
other forms of air pollution. Grantz et al. [55]
provides Guderian’s categories of effects of air
pollutants on ecosystems:
• Accumulation of pollutants in plants and other
ecosystem components (e.g., soil, water)
• Damage to humans as a result of pollutant
accumulation
• Shifts in competition causing changes in species diversity
• Disruption of biogeochemical cycles
• Disruption of stability and reduction in selfregulation capabilities
• Breakdown of stands and associations
• Expansion of denuded zones
Many of these types of impacts have been
observed and linked to particular pollutants. For
example, mercury has been shown to be toxic to
microorganisms, plants, and animals [56], and toxicity of other heavy metals such as lead has also been
confirmed [19]. By binding to proteins, mercury can
also accumulate in organisms and ecosystems [21].
Ground-level ozone (O 3 ) is a known hazard,
leading to reduced production of fine roots in
some trees [57], reduced tree growth [58], and
damage to a plant’s photosynthetic systems
[59]. The reduced activity of plant life as a result
of ozone will reduce an ecosystem’s ability to
store carbon and thereby exacerbates climate
change [60]. Damage and reduced yields of plants
will reduce the availability of food for wild animals, stressing those populations as well.
Visibility
Air Pollution (mostly particles) can reduce visibility. Severe visibility problems arising from
poor air quality have recently been experienced
in some Chinese cities [61]. Human enjoyment of
the environment is impeded by poor visibility and
in extreme cases poor visibility poses a safety
hazard in aviation.
Air Pollution Monitoring and Sustainability
393