Download IIS VIOLA MARCHESINI CLIL MODULE “AIR POLLUTION” A.S.

IIS VIOLA MARCHESINI CLIL MODULE “AIR POLLUTION”
2) AIR POLLUTION
Air pollution may be defined as any
atmospheric condition in which substances
are present at concentrations high enough
above their normal ambient levels to
produce a measurable effect on man,
animals, vegetation, or materials.
Substances
mean
any
natural
or
anthropogenic
(man-made)
chemical
compounds capable of being airborne. They
may exist in the atmosphere as gases, liquid
drops, or solid particles.
The science of air pollution centers on
measuring, tracking, and predicting
concentrations of key chemicals in the
atmosphere.
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reaction (such as photosynthesis) or
because they are scavenged from the
atmosphere and carried to Earth by rain,
snow, or fog.
Air pollution trends are strongly affected by
atmospheric
conditions
such
as
temperature, pressure, and humidity, and
by global circulation patterns. For example,
winds carry some pollutants far from their
sources across national boundaries and
even across the oceans.
Transport is fastest along east-west routes:
longitudinal winds can move air around the
globe in a few weeks, compared to months
or longer for air exchanges from north to
south.
Four types of processes affect air pollution
levels
· Emissions. Chemicals are emitted to the
atmosphere by a range of sources.
Anthropogenic emissions come from human
activities, such as burning fossil fuel.
Biogenic emissions are produced by natural
functions of biological organisms, such as
microbial breakdown of organic materials.
Emissions can also come from non living
natural sources, most notably volcanic
eruptions and desert dust.
· Chemistry. Many types of chemical
reactions in the atmosphere create, modify,
and destroy chemical pollutants.
· Transport. Winds can carry pollutants far
from their sources, so that emissions in one
region cause environmental impacts far
away. Long-range transport complicates
efforts to control air pollution because it
can be hard to distinguish effects caused by
local versus distant sources and to
determine who should bear the costs of
reducing emissions.
· Deposition. Materials in the atmosphere
return to Earth, either because they are
directly absorbed or taken up in a chemical
Local weather patterns also interact with
and affect air pollution. Rain and snow carry
atmospheric
pollutants
to
Earth.
Temperature inversions, like the conditions
that caused London's Great Smog in 1952,
occur when air near the Earth's surface is
colder than air aloft. Cold air is heavier than
warm air, so temperature inversions limit
vertical mixing and trap pollutants near
Earth's surface. Such conditions are often
found at night and during the winter
months.
Stagnation events characterized by weak
winds are frequent during summer and can
lead to accumulation of pollutants over
several days.
Scientists can measure air pollutants
directly when they are emitted—for
example, by placing instruments on factory
smokestacks—or as concentrations in the
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IIS VIOLA MARCHESINI CLIL MODULE “AIR POLLUTION”
ambient outdoor air.
To
track
ambient
concentrations,
researchers create networks of airmonitoring stations, which can be
groundbased or mounted on vehicles,
balloons, airplanes, or satellites.
In the laboratory, scientists use tools
including laser spectrometers and electron
microscopes to identify specific pollutants.
They measure chemical reaction rates in
clear plastic bags ("smog chambers") that
replicate the smog environment under
controlled conditions, and observe emission
of pollutants from combustion and other
sources.
AIR POLLUTANTS CLASSIFICATION.
a) according to chemical composition:
1. Sulfur-containing compounds.
2. Nitrogen-containing compounds.
3. Carbon-containing compounds.
4. Halogen-containing compounds.
5. Toxic substances (any of about).
6. Radiative compounds.
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Knowledge
of
pollutant
emissions,
chemistry,
and
transport
can
be
incorporated into computer simulations
("air quality models") to predict how
specific actions, such as requiring new
vehicle emission controls or cleanerburning fuels, will benefit ambient air
quality. However, air pollutants pass
through many complex reactions in the
atmosphere and their residence times vary
widely, so it is not always straightforward
to estimate how emission reductions from
specific sources will impact air quality over
time.
1. Ozone, O 3.
2. Carbon monoxide, CO.
3. Sulfur dioxide, SO 2.
4. Nitrogen oxides, NO x.
5. Lead, Pb.
6. Particulates, PM10-2,5
7. VOC
8. Radon
b) according to the manner in which they
reach the atmosphere:
1. Primary pollutants (those emitted directly
from the sources).
2. Secondary pollutants (those formed in the
atmosphere by chemical interactions among
primary pollutants and normal atmospheric
conditions).
c) Criteria air pollutants are six major
pollutants defined by EPA (Environmental
Protection Agency) for which ambient air
standards have been set to protect human
health and welfare.
Criteria pollutants (defined by EPA):
1. Ozone, O 3.
2. Carbon monoxide, CO.
3. Sulfur dioxide, SO 2.
4. Nitrogen oxides, NO x.
5. Lead, Pb.
6. Particulates, PM10-2,5
POLLUTANTS STUDIED IN THIS MODULE
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