The document discusses various topics related to atmospheric chemistry and air pollution. It begins with an overview of the composition and structure of the atmosphere, including the different layers (troposphere, stratosphere, mesosphere, thermosphere). It then covers various atmospheric reactions and processes, such as photochemical reactions, lapse rates, temperature inversions, and ozone layer formation and depletion. The document also discusses different air pollutants, their sources, effects, and methods for air quality monitoring and pollution control. Finally, it touches on related issues like the greenhouse effect, global warming, acid rain, and indoor air pollution.
Forensic Biology & Its biological significance.pdf
1 Unit Atmosphere .pptx
1. Dr. Pranjali Bisht
Assistant Professor
Department of Chemistry
MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY
Bhopal
Subject – Environmental Chemistry
Subject Code – CH 123
3. ATMOSPHERE AND AIR POLLUTION
Atmospheric composition
Structure of Atmosphere
Atmospheric reactions
Photochemical reactions in atmosphere
Lapse rate
Temperature inversion
Types of inversions
Smog formation - causes, effects and control with reactions
Ozone layer - mechanism of ozone depletion
4. Classification and Effects of Air Pollutants (Oxides of S, C, N,
Hydrocarbons and Particulates)
Air quality index, Ways of Monitoring, Prevention and control of Air
Pollution
Greenhouse effect and Global warming - major sources, effects and
remedial measures
Acid rain and their adverse effects, Indoor Pollution - causes and
effects
Volatile Organic Compounds – origin and negative effects
5. Environment studies basically concern with the
learning the way we should live with our
surrounding.
It helps individual to develop an understanding
of living in physical environment & how to
resolve present environmental issues around.
It helps to develop sustainable environment
conditions for the better growth for us.
7. What is the Atmosphere
The thin envelope or blanket of gases forming a protective covering
around the Earth.
It consists of mixture of gases that surrounds the planet & are
essential for photosynthesis and other activities of life.
Because of atmosphere life is possible on earth as all living animals &
plants on the earth need the atmosphere to survive.
Earth's atmosphere consists of about 78% nitrogen, 21% oxygen and
0.93% argon.
The remaining gas which is less than 0.1%, contains carbon dioxide,
nitrous oxides, methane, helium, neon and ozone.
8.
9.
10. AURORA –
They lie about 1,300
kilometers (800 miles) from
the geographic poles, but are
slowly moving. In the
ionosphere, the ions of the
solar wind collide with atoms
of oxygen and nitrogen from
the Earth's atmosphere. The
energy released during these
collisions causes a colorful
glowing halo around the
poles.
11. • Meteoroid: A “space rock”—a relatively small object
traveling through space, between the size of a grain of
dust and a small asteroid.
• Meteor: A meteoroid that enters Earth’s atmosphere
and burns up.
• Meteorite: A meteoroid, especially one that has hit
Earth’s surface.
• Asteroid: A rocky object that orbits the sun and has an
average size between a meteoroid and a planet.
• Comet : an object made of ice and dust, often with gas
halo and tail and sometimes it orbits the sun.
12. Importance of the Atmosphere
It provides oxygen to breathe.
It regulates water cycle & plays important role in precipitation.
It protects us from harmful ultraviolet (UV) radiation coming from
the Sun.
It keeps the surface of earth warm by the greenhouse effect &
prevents extreme differences between day and night temperatures.
It regulate Earth’s climate.
It creates the pressure without which liquid water couldn’t exist on
Earth’s surface.
The gases of the atmosphere even allow us to hear.
13. The layer closest to the surface is the troposphere, which
contains over 80% of the atmospheric mass and nearly all the
water vapor.
The next layer, the stratosphere, contains most of the
atmosphere’s ozone, which absorbs high-energy radiation from
the SUN and makes life on the surface possible.
Above the stratosphere are the mesosphere and thermosphere.
These two layers include regions of charged atoms and
molecules, or ions.
The upper mesosphere and lower thermosphere are called the
ionosphere, this region is important to radio communications,
because radio waves can bounce off the layer and travel great
distances.
17. Earth's atmosphere is
composed of about 78%
nitrogen, 21% oxygen, and
0.93% argon.
The remainder, less than
0.1%, contains such trace
gases as water vapor,
carbon dioxide, and ozone.
The atmosphere can be
divided into vertical layers
determined by the way
temperature changes with
altitude.
18. As you increase in elevation, there is less air
above you thus the pressure decreases.
As the pressure decreases, air molecules
spread out further (i.e. air expands), and the
temperature decreases.
If the humidity is at 100 percent (because it's
snowing), the temperature decreases more
slowly with height.”
19. What is lapse rate?
Lapse rate is the rate at which the temperature in the earth's atmosphere increases with a
decrease in altitude or decreases with the increase in the altitude.
The temperature decreases at the rate of 1° C for every 165 meters of height.
The rate of temperature change with altitude, the “lapse rate,” is by definition is the
negative of the change in temperature with altitude, i.e., −dT/dz.
There are three types of lapse rates that are used to express the rate of temperature
change with a change in altitude, namely the dry adiabatic lapse rate, the wet adiabatic
lapse rate and the environmental lapse rate.
The lapse rate is considered positive when the temperature decreases with elevation, zero
when the temperature is constant with elevation, and negative when the temperature
increases with elevation (temperature inversion).
20. Q What is the difference between environmental
lapse rate and adiabatic lapse rate?
The environmental lapse rate refers to the
temperature drop with increasing altitude in the
troposphere; that is the temperature of the
environment at different altitudes.
It implies no air movement.
Adiabatic cooling is associated only with ascending
air, which cools by expansion.
21.
22. Most prevalent gases are nitrogen (78%)
and oxygen (21%), with the remaining 1- %
consisting of argon, (0. 9%) and traces
of hydrogen ozone ( a form of oxygen), and
other constituents.
Temperature and water vapor content in the
troposphere decrease rapidly with altitude.
23. Reactions taking place in troposphere
The troposphere is the lowest region and lies just above the surface of
the earth. When sunlight enters the troposphere, carbon dioxide and
water vapor molecules present in this region absorb a large amount of
energy and gets excited as per the following reaction:
CO2
𝒉𝒗
CO2 (excited)
H2O
𝒉𝒗
H2O (excited)
These excited molecules then combine with other molecules, thus
increasing the temperature of the atmosphere. These two molecules may
also react forming carbonic acid.
H2O + CO2 → H2CO3
24. Troposphere Reactions
1. Formation of OH- radical-
O3 + hv O + O2 (λ ≤ 310 nm)
O + O2 O3 + M
O + H2O 2OH-
2. Reactions of NO2, CO & CH4
NO2 + O2 + hv NO + O3
CO + 2O2 + hv CO2 + O3
CH4 + 4O2 + 2hv HCHO + H2O + 2O3
25.
26. Peroxyacyl nitrates (also known as Acyl peroxy nitrates, APN or PANs) are
powerful respiratory and eye irritants present in photochemical smog.
They are nitrates produced in the thermal equilibrium between
organic peroxy radicals by the gas-phase oxidation of a variety of volatile
organic compounds (VOCs), or by aldehydes and other oxygenated VOCs
oxidizing in the presence of NO2.
Peroxyacetyl nitrate (CH3CO·O2NO2, abbreviated as PAN) is a trace molecular
species present in the troposphere and lower stratosphere due primarily to
pollution from fuel combustion and the pyrogenic outflows from biomass
burning.
PAN is formed by oxidation of non-methane volatile organic compounds
(NMVOCs) in the presence of NOx.
NMVOCs and NOx have both natural and anthropogenic sources.
27. In the Stratosphere, ultraviolet light reacts
with O 2 molecules to form atomic oxygen.
Atomic oxygen then reacts with an
O 2 molecule to produce ozone (O 3).
As a result of this reaction,
the Stratosphere contains an appreciable
concentration of ozone molecules that
constitutes the ozone layer.
28. The pattern of temperature increase with height in
the stratosphere is the result of solar heating as
ultraviolet radiation in the wavelength range of
0.200 to 0.242 micrometer which dissociates
diatomic oxygen (O2).
The resultant attachment of single oxygen atoms
to O2 produces ozone (O3).
29. Ozone is naturally produced in
the stratosphere by a two- step reactive process.
In the first step, solar ultraviolet radiation
(sunlight) breaks apart an oxygen molecule to
form two separate oxygen atoms.
In the over- all process, three oxygen molecules
plus sunlight react to form two ozone molecules.
30.
31. The mesosphere is very important for earth's
protection.
The mesosphere burns up most meteors and
asteroids before they are able to reach the earth's
surface.
The mesosphere is the coldest atmospheric layer
surrounding the earth.
It becomes cold enough to freeze water vapour in
its atmosphere into ice clouds.
32. The percentage of oxygen, nitrogen,
and carbon dioxide in the air in the
mesosphere is essentially the same as that in
the levels of the Earth's atmosphere
immediately above the Earth's surface.
Atomic oxygen is notoriously difficult to
measure, especially with remote sensing
techniques from orbiting satellite sensors
33. O + OH H + O2
H + O2 + M HO2 + M
H + O3 OH + O2
O + O + M O2 + M
O + O2 + M O3 + M
O + O3 O2 + O2
34. The layer present right above the mesosphere
extending to a height of 450 km is the
thermosphere.
This layer is composed of electrically charged ions
that are responsible for reflecting the radio waves
back to the Earth's surface.
Due to the presence of these ions,
thermosphere is also known as ionosphere.
35. The Ionosphere is ionized by solar radiation.
It plays an important role in atmospheric
electricity and forms the inner edge of the
magnetosphere.
It has practical importance because, among
other functions, it influences radio
propagation to distant places on the Earth.
36.
37. In the upper thermosphere, atomic oxygen (O),
atomic nitrogen (N), and helium (He) are the main
components of air.
Much of the X-ray and UV radiation from the Sun
is absorbed in the thermosphere.
When the Sun is very active and emits more high-
energy radiation, the thermosphere gets hotter
and expands or "puffs up".
38. Photochemical smog is
produced when sunlight
reacts with nitrogen oxides
and at least one volatile
organic compound (VOC) in
the atmosphere. Nitrogen
oxides come from car
exhaust, coal power plants,
and factory emissions.
VOCs are released from
gasoline, paints, and many
cleaning solvents.
39. At least two distinct types
of smog are recognized:
sulfurous smog
and photochemical smog.
Sulfurous smog, which is
also called “London smog,”
results from a high
concentration of sulfur
oxides in the air and is
caused by the use of
sulfur-bearing fossil fuels,
particularly coal.
40. This kind of visible air pollution is composed
of nitrogen oxides, sulphur oxides, ozone,
smoke and other particulates.
Man-made smog is derived from coal
combustion emissions, vehicular emissions,
industrial emissions, forest and agricultural
fires and photochemical reactions of these
emissions.
41. Photochemical smog happens when nitrogen
oxides and volatile organic compounds react
together in the presence of sunlight as a catalyst
and form ozone at lower levels.
The nitrogen oxides come from vehicle exhausts,
and volatile organic compounds come from many
chemicals, such as paint and cleaning agents.
NO2 + VOC O3 + NO
42. Photochemical smog, which is also known as “Los Angeles smog,” occurs most prominently
in urban areas that have large numbers of automobiles. It requires neither smoke nor fog. This
type of smog has its origin in the nitrogen oxides and hydrocarbon vapours emitted by
automobiles
Alternative Reactions -
NO and NO2 can also react with the hydrocarbons instead of ozone to form other volatile
compounds known as PAN (peroxyacetyl nitrate).
The accumulation of ozone and volatile organic compounds along with the energy from
the sun forms the brown, photochemical smog seen on hot, sunny days.
43.
44.
45. Why is it harmful?
When inhaled, smog irritates our airways,
increasing our risk of
serious heart and lung diseases.
These health risks are the reasons for why many
cities monitor smog levels.
On a high ozone-alert day, for example,
your eyes and throat may burn, and you may cough
and wheeze.
47. Mobile sources – such as cars, buses, planes,
trucks, and trains.
Stationary sources – such as power plants, oil
refineries, industrial facilities, and factories.
Area sources – such as agricultural areas,
cities, and wood burning fireplaces.
Natural sources – such as wind-blown dust,
wildfires, and volcanoes.
48. Particulate matter is the sum of all solid and
liquid particles suspended in air many of
which are hazardous.
This complex mixture includes both organic
and inorganic particles, such as dust, pollen,
soot, smoke, and liquid droplets.
These particles vary greatly in size,
composition, and origin.
49. Both terms aerosol and particulate matter describe the
particles in the air.
The key difference between aerosol and particulate matter
is that aerosol refers to a collection of suspended particles
and the surrounding gases, whereas particulate matter
refers to the suspended solid or liquid matter in the air.
50. These are dispersed solid or liquid particles
of microscopic size in gaseous media.
Particulates can either be natural or
anthropogenic.
Dust, smoke, fly ash, fumes, mist etc comes
under particulate matter.
59. AQI : Air quality Index is a numerical value and
ratio derived form the series of observations for
reporting daily air quality.
It tells us how clean and polluted our air is and
what associated health effects might be concern.
AQI usually calculate main five major air
pollutants, they are CO, SO2, O3, NO2, dust and
smoke.
60.
61. The greenhouse effect is a natural process that warms the Earth's
surface.
When the Sun's energy reaches the Earth's atmosphere, some of
it is reflected back to space and the rest is absorbed and re-
radiated by greenhouse gases.
The absorbed energy warms the atmosphere and the surface of
the Earth.
The greenhouse effect is caused by the atmospheric
accumulation of gases such as carbon dioxide and methane,
which contain some of the heat emitted from Earth's surface.
The atmosphere allows most of the visible light from the Sun to
pass through and reach Earth's surface.
62. Greenhouse gases keep our
planet livable by holding
onto some of Earth's heat
energy so that it doesn't all
escape into space. This heat
trapping is known as
the greenhouse effect. Just
as too little greenhouse
gas makes Earth too cold,
too much greenhouse
gas makes Earth too warm.
63. Maintain Temperature
Levels.
They help in maintaining a
certain temperature level on
the earth's surface.
Block Harmful Radiations.
They help in blocking
harmful solar radiation
from reaching the planet's
surface.
Maintains Water Level.
64. greenhouse effect are
quite evident: Global
warming.
The increasing amount
of greenhouse gases are
causing a gradual rise in
the earth's temperature.
As a result, the ice in the
Polar Regions has started
melting and resulting in
massive climate changes.
65.
66. Global warming, the
gradual heating of Earth's
surface, oceans and
atmosphere, is caused by
human activity, primarily
the burning of fossil
fuels that pump carbon
dioxide (CO2), methane
and other greenhouse
gases into the
atmosphere.
67.
68. Acid rain, or acid
deposition, is a broad term
that includes any form
of precipitation with acidic
components, such as
sulfuric or nitric acid that
fall to the ground from the
atmosphere in wet or dry
forms.
This can include rain, snow,
fog, hail or even dust that
is acidic
69.
70. Airborne particles can be removed from a polluted airstream by a
variety of physical processes.
Common types of equipment for collecting fine particulates include
cyclones, scrubbers, electrostatic precipitators, and baghouse filters.
Once collected, particulates adhere to each other, forming
agglomerates that can readily be removed from the equipment and
disposed of, usually in a landfill.
71. An electrostatic precipitator is a type of filter (dry scrubber) that uses
static electricity to remove soot and ash from exhaust fumes before they
exit the smokestacks.
This one common air pollution control device.
Most power stations burn fossil fuels such as coal or oil to generate
electricity for use.
72. An electrostatic
precipitator (ESP) is a
filter less device
that removes fine particles,
like dust and smoke, from a
flowing gas using the force
of an induced electrostatic
charge minimally impeding
the flow of gases through
the unit.
73. A cyclone removes particulates by causing the dirty airstream to flow in a spiral path inside
a cylindrical chamber.
Dirty air enters the chamber from a tangential direction at the outer wall of the device,
forming a vortex as it swirls within the chamber.
The larger particulates, because of their greater inertia, move outward and are forced
against the chamber wall. Slowed by friction with the wall surface, they then slide down the
wall into a conical dust hopper at the bottom of the cyclone.
The cleaned air swirls upward in a narrower spiral through an inner cylinder and emerges
from an outlet at the top. Accumulated particulate dust is periodically removed from the
hopper for disposal.
