INTRODUCTION

Environmental chemistry is the scientific study of the chemical and

biochemical phenomena that occur in natural places. It can be defined as
the study of the sources, reactions, transport, effects, and fates of
chemical species in the air, soil, and water environments; and the effect of
human activity and biological activity on these. It includes topics such as
astrochemistry, atmospheric chemistry, environmental modelling,
geochemistry, marine chemistry and pollution remediation.
The environment can be divided into 4 spheres:
• Lithosphere: The lithosphere, sometimes called the geosphere, refers to
all of the rocks of the earth. It includes the planet's mantle and crust, the
two outermost layers.
• Hydrosphere: This sphere contains all the water bodies on Earth, like
river, ponds and lakes.
• Atmosphere: The atmosphere is the body of gasses that surrounds our
planet, held in place by earth's gravity. Most of our atmosphere is located
close to the earth's surface where it is most dense.
• Biosphere: The biological envelope surrounding the globe which
contains life and is able to sustain life without the help of any artificial
system is termed as biosphere. The energy requirement of biosphere for
sustaining life is met by the sun, mainly through the process known as
photosynthesis.
ENVIRONMENTAL POLLUTION AND POLLUTANTS
Pollution is the introduction of contaminants into the natural environment
that cause adverse change. Environmental pollution is the unfavorable
alteration of our surroundings, wholly or largely as a byproduct of man’s
actions, through direct or indirect effects of the changes in the energy
pattern, radiation levels, and chemical and physical constitution and
abundance of organisms. Pollutants, the components of pollution, can be
either foreign substances/energies or naturally occurring contaminants.
Pollutants damage the quality of air, water, and land.
ENVIRONMENTAL POLLUTANTS
The physical, chemical and biological agents which, when released into
the environment, adversely affect the human interests are called
pollutants. Types of pollutants in our environment:
 Physical pollutants: The physical factors which cause unbearable
effects on the human system and its surroundings are called
physical pollutants.
 Chemical pollutants: Harmful gases such as CO, SO2 , S, heavy
metals, petroleum and radioactive substances are some important
chemical pollutants.
 Biological pollutants: Important biological pollutants are certain
microorganisms and overpopulation.
Odum (1971) can be classified into:
 Non-degradable pollutants: The substances which either do not
degrade or degrade very slowly in natural environment are called
non-biodegradable pollutants.
 Biodegradable pollutants: Substances which degrade readily in
natural environment by microorganisms are called biodegradable
pollutants.
AIR POLLUTION
Air pollution is the presence of substances in the atmosphere that are
harmful to the health of humans and other living beings, or cause damage
to the climate or to materials. There are many different types of air
pollutants, such as gases (including ammonia, carbon monoxide, sulphur
dioxide, nitrous oxides, methane, carbon
dioxide and chlorofluorocarbons), particulates (both organic and
inorganic), and biological molecules. 

TYPES OF AIR POLLUTNATS

• Primary pollutants: Pollutants which are emitted directly from the
sources are called primary pollutants.
• Secondary pollutants: Pollutants which come into existence in the
atmosphere on account of chemical reactions involving primary pollutants
are called secondary pollutants.
MAJOR AIR POLLUTANTS
• Carbon dioxide: Because of its role as a greenhouse gas it has been
described as "the leading pollutant" and "the worst climate pollutant".
Carbon dioxide is a natural component of the atmosphere, essential for
plant life and given off by the human respiratory system. CO2 increase in
earth's atmosphere has been accelerating

• Oxides of Sulphur: Particularly sulphur dioxide, a chemical compound

with the formula SO2. SO2 is produced by volcanoes and in various
industrial processes. Coal and petroleum often contain sulphur
compounds, and their combustion generates sulphur dioxide. Further
oxidation of SO2, usually in the presence of a catalyst such as NO2,
forms H2SO4, and thus acid rain is formed. This is one of the causes for
concern over the environmental impact of the use of these fuels as power
sources.

• Oxides of Nitrogen: Nitrogen oxides, particularly nitrogen dioxide, are

expelled from high temperature combustion, and are also produced during
thunderstorms by electric discharge. They can be seen as a brown haze
dome above or a plume downwind of cities. Nitrogen dioxide is a
chemical compound with the formula NO2. It is one of several nitrogen
oxides. One of the most prominent air pollutants, this reddish-brown toxic
gas has a characteristic sharp, biting odour. •
Carbon monoxide: CO is a colourless, odourless, toxic gas. It is a
product of combustion of fuel such as natural gas, coal or wood.
Vehicular exhaust contributes to the majority of carbon monoxide let into
our atmosphere. It creates a smog type formation in the air that has been
linked to many lung diseases and disruptions to the natural environment
and animals. •
Volatile Organic Compounds: VOCs are a well-known outdoor air
pollutant. They are categorized as either methane (CH4) or non-methane
(NMVOCs). Methane is an extremely efficient greenhouse gas which
contributes to enhanced global warming. Other hydrocarbon VOCs are
also significant greenhouse gases because of their role in creating ozone
and prolonging the life of methane in the atmosphere. This effect varies
depending on local air quality. •
Chlorofluorocarbons (CFCs): They are harmful to the ozone layer and
are emitted from products which are currently banned from use. These are
gases which are released from air conditioners, refrigerators, aerosol
sprays, etc. On release into the air, CFCs rise to the stratosphere. Here
they come in contact with other gases and damage the ozone layer. This
allows harmful ultraviolet rays to reach the earth's surface. This can lead
to skin cancer, eye disease and can even cause damage to plants. •
Particulate Matter: Some particulates occur naturally, originating from
volcanoes, dust storms, forest and grassland fires, living vegetation, and
sea spray. Human activities, such as the burning of fossil fuels in vehicles,
power plants and various industrial processes also generate significant
amounts of aerosols. Averaged worldwide, anthropogenic aerosols—
those made by human activities—currently account for approximately 10
percent of our atmosphere. Increased levels of fine particles in the air are
linked to health hazards such as heart disease, altered lung function and
lung cancer. Particulates are related to respiratory infections and can be
particularly harmful to those already suffering from conditions like
asthma. •
Ammonia: Emitted mainly by agricultural waste. Ammonia is a
compound with the formula NH3. It is normally encountered as a gas with
a characteristic pungent odour. Ammonia contributes significantly to the
nutritional needs of terrestrial organisms by serving as a precursor to
foodstuffs and fertilizers. Although in wide use, ammonia is both caustic
and hazardous. In the atmosphere, ammonia reacts with oxides of
nitrogen and sulphur to form secondary pollutants

 Odors — such as from garbage, sewage, and industrial

processes
 Radioactive pollutants – produced by nuclear explosions,
nuclear events, war explosives, and natural processes such as
the radioactive decay of radon.

Secondary pollutants include:

 Particulates created from gaseous primary pollutants and

compounds in photochemical smog. Smog is a kind of air
pollution. Classic smog results from large amounts of coal
burning in an area caused by a mixture of smoke and sulfur
dioxide. Modern smog does not usually come from coal but
from vehicular and industrial emissions that are acted on in the
atmosphere by ultraviolet light from the sun to form secondary
 pollutants that also combine with the primary emissions to form
photochemical smog.
 Ground level ozone (O3) formed from NOx and VOCs. Ozone
(O3) is a key constituent of the troposphere. It is also an
important constituent of certain regions of the stratosphere
commonly known as the Ozone layer. Photochemical and
chemical reactions involving it drive many of the chemical
processes that occur in the atmosphere by day and by night. At
abnormally high concentrations brought about by human
activities (largely the combustion of fossil fuel), it is a pollutant
and a constituent of smog.
 Peroxyacetyl nitrate (C2H3NO5) – similarly formed from
NOx and VOCs.

SOURCES OF AIR POLLUTANTS

• Anthropogenic (Human-made) Sources: Smoke stacks of
fossil fuel power stations, manufacturing facilities (factories)
and waste incinerators, as well as furnaces and other types of
fuel-burning heating devices produce air pollutants. In
developing and poor countries, traditional biomass burning is
the major source of air pollutants. Motor vehicles, trains, marine
vessels and aircraft produce a large amount of exhaust gases
including Carbon dioxide and Carbon monoxide.
 • Natural Sources: Dust from natural sources, smoke from
wildfires and methane by digestion of food from animals.
Radon gas from radioactive decay within the Earth's crust.
Radon is a colorless, odorless, naturally occurring,
radioactive noble gas that is formed from the decay of radium.
It is considered to be a health hazard. Radon gas from natural
sources can accumulate in buildings, especially in confined
areas such as the basement and it is the second most frequent
cause of lung cancer, after cigarette smoking.

 Smoke and carbon monoxide from wildfires. During periods of

active wildfires, smoke from uncontrolled biomass combustion
can make up almost 75% of all air pollution by concentration.[36]
 Vegetation, in some regions, emits environmentally significant
amounts of volatile organic compounds (VOCs) on warmer
days. These VOCs react with primary anthropogenic pollutants
—specifically, NOx, SO2, and anthropogenic organic carbon
compounds — to produce a seasonal haze of secondary
pollutants.[37] Black gum, poplar, oak and willow are some
examples of vegetation that can produce abundant VOCs. The
 VOC production from these species result in ozone levels up to
eight times higher than the low-impact tree species.[38]
 Volcanic activity, which produces sulfur, chlorine, and ash
particulates
CONTROL OF AIR POLLUTION
• Using public transports: Using public transport contributes to less air
pollution as it provides with less gas and energy, even carpools contribute
to it. In addition to less release of fuels and gas, using a public transport
can also help in saving money.
• Reuse, Reduce and Recycle: The concept of recycle and reuse is not
just conserve resources and use them judicially but also is helpful for air
pollution as it helps in reducing pollution emissions. The recycled
products also take less power to make other products.

• Reduction of forest fires and smoking: The collecting of garbage and

getting it on fire in dry seasons or dry leaves catching fires is a huge
factor for causing air pollution, moreover smoking also causes air
pollution and causes the air quality to worsen along with obviously
damaging one’s health.
• Implementing afforestation: The practice of planting trees provides a
lot of benefits to the environment and helps with the release of oxygen. It
also reduces air pollution and increases the quality of air.
 Use filters for chimneys:The gas that is emitted from fireplaces
in homes and factories are extremely dangerous for air pollution
and harms the air quality severely. The use of filters should be
used at least if the consumption couldn’t be lessened, this will
help to reduce the effect of harmful gases absorbing in the air.
SMOG
Smog is a type of intense air pollution .The term "smog" was first used in
the early 1900s to describe a mix of smoke and fog. The smoke usually
came from burning coal. Smog was common in industrial areas, and
remains a familiar sight in cities today. Today, most of the smog we see
is photochemical smog. Photochemical smog is produced when sunlight
reacts with nitrogen oxides and at least one volatile organic compound
(VOC) in the atmosphere.
TYPES OF SMOG:
• London smog: Sulphurous smog, which is also called “London smog”
and “Industrial smog” results from a high concentration of sulphur oxides
in the air and is caused by the use of sulphur bearing fossil fuels,
particularly coal. This type of smog is aggravated by dampness and a high
concentration of suspended particulate matter in the air. It causes
bronchial irritation, poor atmospheric visibility and acid rain.

• Photochemical smog: 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 and other sources, which then undergo
photochemical reactions in the lower atmosphere. The highly toxic gas
ozone arises from the reaction of nitrogen oxides with hydrocarbon
vapours in the presence of sunlight, and some nitrogen dioxide is
produced from the reaction of nitrogen oxide with sunlight. The resulting
smog causes a light brownish coloration of the atmosphere, reduced
visibility, plant damage, irritation of the eyes, and respiratory distress.
FORMATION OF PHOTOCHEMICAL SMOG
The reactions involved in formation of photochemical smog are:
• The hydrocarbons and oxides of nitrogen released by automobiles get
accumulated in the atmosphere.

• Nitrogen dioxide thus accumulated in the atmosphere absorbs sunlight

in the blue and near ultraviolent region of the spectrum and decomposes
into nitric oxide and atomic oxygen.

• NO is converted into NO2 with the simultaneous formation of ozone and

aldehydes.

• The hydrocarbons present in the atmosphere undergo oxidation to form

a number of secondary pollutants such as formaldehyde, acrolein,
peroxyacetyl nitrates (PAN), these secondary pollutants form haze like
aerosols which constitute the photochemical smog.
MEASURES TO REDUCE SMOG
Formation of smog can be reduced by decreasing the concentration of
nitrogen oxides and hydrocarbons in the atmosphere. This could be
achieved by using catalytic converters in automobiles. The catalytic
converters reduce the quality of hydrocarbons and nitrogen oxides in the
smoke coming out of exhaust pipes of automobiles. XIV
ACID RAIN
Acid rain is a rain or any other form of precipitation that is unusually
acidic, meaning that it has elevated levels of hydrogen ions (low pH). It
can have harmful effects on plants, aquatic animals, and infrastructure.
FORMATION OF ACID RAIN
Acid rain is caused by a chemical reaction that begins when compounds
like sulphur dioxide and nitrogen oxides are released into the air. These
substances can rise very high into the atmosphere, where they mix and
react with water, oxygen and other chemicals to form acidic pollutants,
known as acid rain.
EFFECTS OF ACID RAIN
• Effects on fish and wildlife: The ecological effects of acid rain are
most clearly seen in aquatic environments, such as streams, lakes, and
marshes where it can be harmful to fish and other wildlife. As it flows
through the soil, acidic rain water can leach aluminium from soil clay
particles and then flow into streams and lakes. Generally, the young of
most species are more sensitive to environmental conditions than adults.
At pH 5, most fish eggs cannot hatch. At lower pH levels, some adult fish
die. Some acidic lakes have no fish. Even if a species of fish or animal
can tolerate moderately acidic water, the animals or plants it eats might
not.
Effects on plants and trees: Dead or dying trees are a common sight in
areas effected by acid rain. Acid rain leaches aluminium from the soil.
That aluminium may be harmful to plants as well as animals. Acid rain
also removes minerals and nutrients from the soil that trees need to grow.
At high elevations, acidic fog and clouds might strip nutrients from trees’
foliage, leaving them with brown or dead leaves and needles. The trees
are then less able to absorb sunlight, which makes them weak and less
able to withstand freezing temperatures.
MEASURES TO REDUCE ACID RAIN
• Use lesser energy so that lesser fuel is burnt.

• Use cleaner fuels.

• Remove oxides of sulphur and oxides of nitrogen before releasing the

air into atmosphere.
OZONE LAYER
The ozone layer or ozone shield is a region of Earth's stratosphere that
absorbs most of the Sun's ultraviolet radiation. It contains a high
concentration of ozone (O3) in relation to other parts of the atmosphere,
although still small in relation to other gases in the stratosphere. The
ozone layer contains less than 10 parts per million of ozone, while the
average ozone concentration in Earth's atmosphere as a whole is about 0.3
parts per million. The ozone layer is mainly found in the lower portion of
the stratosphere, from approximately 15 to 35 kilometers (9 to 22 mi)
above Earth, although its thickness varies seasonally and geographically.

FORMATION OF OZONE IN STRATOSPHERE

Stratospheric ozone is formed naturally through the interaction of solar
ultraviolet (UV) radiation with molecular oxygen (O2).
DEPLETION OF OZONE LAYER
When chlorine and bromine atoms come into contact with ozone in the
stratosphere, they destroy ozone molecules. One chlorine atom can
destroy over 100,000 ozone molecules before it is removed from the
stratosphere. Ozone can be destroyed more quickly than it is naturally
created
some compounds release chlorine or bromine when they are exposed to
intense UV light in the stratosphere. These compounds contribute to
ozone depletion, and are called ozone-depleting substances (ODS). ODS
that release chlorine include chlorofluorocarbons (CFCs),
hydrochlorofluorocarbons (HCFCs), carbon tetrachloride, and methyl
chloroform. ODS that release bromine include halons and methyl
bromide. XVIII
WATER POLLUTION
water pollution is the release of substances into
subsurface groundwater or into lakes, streams, rivers, estuaries,
and oceans to the point where the substances interfere with beneficial use
of the water or with the natural functioning of ecosystems. In addition to
the release of substances, such as chemicals or microorganisms, water
pollution may also include the release of energy, in the form
of radioactivity or heat, into bodies of water.

MAJOR WATER POLLUTANTS

• Microbial pollutants: Pathogens can be bacteria, protozoa or viruses.
Bacteria, for example, are commonly found in water. However, when
they start to increase above safe levels, water contamination occurs. Some
examples of microorganisms found in water that cause diseases are
Salmonella, Giardia lamblia, Norovirus, Cryptosporidium parvum, and E.
coli.
• Organic material: Organic materials are things like petroleum,
insecticides and herbicides, detergents, disinfecting cleaners, and
prescription drugs. One of the most frequently detected highly toxic
organic chemicals is methyl tert-butyl ether. Water contaminated with this
organic chemical can cause leukaemia, lymphoma and tumors in the
testicles, thyroid glands and kidneys.
• Inorganic material: Inorganic materials include things like ammonia,
chemical waste, fertilizers, and heavy metals. Heavy metals like arsenic,
mercury, copper, chromium, zinc and barium though harmless in very
small amounts, act as pollutants when they end up concentrated in water.
This can be due to leaching from waste disposal areas. This kind of water
pollution, especially in higher concentrations, can cause severe health
problems in humans and other organisms, including death.
• Macroscopic pollutants: Macroscopic pollutants are large, visible
items in waterways or bodies of water. Trash, either intentionally dumped
into bodies of water, or discarded on the ground and washed by rainfall
into storm drains, are eventually discharged into waterways. This has led
to the formation of the "great Pacific garbage patch," which is now the
size of France. These larger pollutants must be removed in order to avoid
disruption of aquatic ecosystems and contamination upon the chemical
breakdown of these objects.
• Thermal pollutants: Thermal pollution is the rise or fall in the
temperature of a natural body of water caused by human influence. A
common cause of thermal pollution is the use of water as a coolant by
power plants and industrial manufacturers. It can also be caused by the
release of very cold water from the base of reservoirs into warmer rivers.
Elevated water temperatures decrease oxygen levels, which can kill fish
and alter food chain composition, and reduce species biodiversity. Urban
runoff may also elevate temperature in surface waters.
SOIL POLLUTION
Soil pollution is defined as the presence of toxic chemicals (pollutants or
contaminants) in soil, in high enough concentrations to pose a risk to
human health and/or the ecosystem. In the case of contaminants which
occur naturally in soil, even when their levels are not high enough to pose
a risk, soil pollution is still said to occur if the levels of the contaminants
in soil exceed the levels that should naturally be present.
MAJOR SOIL POLLUTANTS
• Heavy metals: The presence of heavy metals (such as lead and mercury,
in abnormally high concentrations) in soils can cause it to become highly
toxic to human beings. Some metals that can be classified as soil
pollutants are Arsenic, Antimony, Lead and Zinc.
• Polycyclic aromatic compounds: Exposure to polycyclic aromatic
hydrocarbons has been linked to several forms of cancer. These organic
compounds can also cause cardiovascular diseases in humans. Soil
pollution due to Polycyclic aromatic compounds can be sourced to coke
(coal) processing, vehicle emissions, cigarette smoke, and the extraction
of shale oil.
• Industrial waste: The discharge of industrial waste into soils can result
in soil pollution. Some common soil pollutants that can be sourced to
industrial waste are chlorinated industrial solvents, dioxins produced from
the manufacture of pesticides and the incineration of waste,
plasticizers/dispersants, polychlorinated biphenyls.
Diseases Caused by Soil Pollution
Humans can be affected by soil pollution through the inhalation of gases
emitted from soils moving upward, or through the inhalation of matter
that is disturbed and transported by the wind because of the various
human activities on the ground. Soil pollution may cause a variety of
health problems, starting with headaches, nausea, fatigue, skin rash, eye
irritation and potentially resulting in more serious conditions like
neuromuscular blockage, kidney and liver damage and various forms of
cancer
GREEN CHEMISTRY
Green chemistry, also called sustainable chemistry, is an area of
chemistry and chemical engineering focused on the design of products
and processes that minimize or eliminate the use and generation of
hazardous substances. While environmental chemistry focuses on the
effects of polluting chemicals on nature, green chemistry focuses on the
environmental impact of chemistry, including reducing consumption of
non-renewable resources and technological approaches for preventing
pollution.
BENEFITS OF GREEN CHEMISTRY
• Cleaner air: Less release of hazardous chemicals to air leading to less
damage to lungs.
• Cleaner water: less release of hazardous chemical wastes to water
leading to cleaner drinking and recreational water
• Increased safety for workers in the chemical industry; less use of toxic
materials; less personal protective equipment required; less potential for
accidents.
• Plants and animals suffer less harm from toxic chemicals in the
environment.
• Lower potential for global warming, ozone depletion, and smog
formation.
• Less chemical disruption of ecosystems.
• Reduced use of petroleum products, slowing their depletion and
avoiding their hazards and price fluctuations.
Higher yields for chemical reactions, consuming smaller amounts of
feedstock to obtain the same amount of product
 BIBLIOGRAPHY

1. https://www.nature.com/subjects/environmental-chemistry
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3. https://en.wikipedia.org/wiki/Air_pollution
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5. ttps://www.nationalgeographic.org/encyclopedia/smog/
6. https://en.wikipedia.org/wiki/Acid_rain
7.https://www3.epa.gov/acidrain/education/site_students/whatcauses.html
8. https://www.epa.gov/acidrain/effects-acid-rain
9. https://www.yourarticlelibrary.com/geography/acid-rain-5-important-
measures-to-control-acid-rain/12370
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science
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water-pollutants
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14. https://www.epa.gov/greenchemistry/benefits-green-chemistry
15. NOOTAN ISC CHEMISTRY CLASS 11 (PART 2) BY DR.H. C.
SRIVASTAVA