The earth has just the right kind of conditions of temperature range, air, water, soil for supporting life and is protected from harmful rays from the outer space by the ozone layer.

With progressive increase in human population and human activities, the quality of air, water, soil and other natural sources get degraded and become unfit for use by organisms.

Increasing population, urbanization and industrialization has led to the decreased availability of water. The quality of water used is also being deteriorated as it is getting more and more polluted.

You may be aware of at least some health hazards and harmful effects of water pollution.

The main components of soil are 90–95%. Inorganic matter and 5–10% organic matter besides soil contains water and air, the composition of the soil varies considerably place to place.

Soil has become dumping ground of most of the waste products. There will be a great loss of earth crust. The dumping of nuclear waste is a world side problem, cause of soil pollution. In this lesson a detailed account of various types, sources and effects of water pollutants is given. Some methods of water pollution control and legislatures involved have also been discussed.

It causes unwanted effects. In this lesson you shall learn about the sources of pollutants and their effects on environment. Thus, the pollution in many ways threaten the existence of many organisms including human being on the earth.

Therefore, any threat of degradation or damage to the environment should be a matter of concern the green chemistry is environment friendly living on design of chemical products with their impacts on human health and on environment. It reduces the use of hazardous substances.

OBJECTIVES

􀁺 define environment and biosphere

􀁺 differentiate the various environmental segments;

􀁺 explain nature of threats to environment;

􀁺 define pollutants and its types;

􀁺 list sources of pollutants and

􀁺 explain the effects of pollutants on environment, organisms and humans in particular.

􀁺 list earth’s water resources;

􀁺 define water pollution and its different parameters;

􀁺 list the major types of water pollutants, their sources and effects;

􀁺 distinguish between natural and man -made pollutants;

􀁺 use the concept of biological oxygen demand (BOD) and account for the changes in a water body;

􀁺 state methods for the prevention of water pollution;

􀁺 compare primary, secondary and tertiary treatment of sewage;

􀁺 identify the sources of soil pollution;

􀁺 how to control of soil pollution,

􀁺 explain the principles of green chemistry;

􀁺 the achievements of green chemistry; and

􀁺 explain strategies to control environmental pollution.

32.1 COMPONENTS OF ENVIRONMENT

Different organisms live in different types of surroundings such as air, water and soil. Different kinds of living organisms share these surroundings. The surroundings are the “environment” of an organism.

Environment has two components

(i) physical or abiotic (non-living) components and (ii) living or biotic components.

Abiotic components of environment are air, water, soil, energy radiation, etc.

Biotic components of environment are microbes (such as bacteria, algae and fungi), plants, animals, etc.

Environment is the sum total of living and non-living components surrounding an organism.

Environment consists of four segments such as

(i) Biosphere (ii) Atmosphere (iii) Hydrosphere, and (iv) Lithosphere

Biosphere: All the parts of the earth are not suitable for survival of organisms.

Some parts are too hot or very cold to support life.

The part of earth on which organisms can survive and reproduce is called biosphere.

Survival of organisms depend upon a delicate balance between themselves and with the various components of the environment. Any disturbance, damage or adverse change in the quality of environment poses a threat to the survival and well-being of organisms. Therefore, any threat of degradation or damage to environment should be a cause of concern to all of us.

Atmosphere: Atmosphere is the only place where free oxygen and water-vapour exist.

Atmosphere is a thin layer of air (mixture of gases) around the earth which is a great source to all living organisms.

Hydrosphere : Water plays an important role in the biosphere, without it life is impossible.

Hydrosphere is the part of earth on which all types of water resources exists, viz., oceans, seas, rivers, lakes, glaciers, ice caps, ground water, etc.

Lithosphere : Soil is a part of lithosphere which supports life.

Lithosphere is the part of the earth where all types of minerals, metals, organic matters, rocks, soils, etc. exist

Global Environmental Damages

Some example of global damages are discuss below.

(i) Chloroflouro carbons (CFCs), used as refrigerants, and various kinds of sprays or sols (eg. perfumes, air freshner, etc.). CFCs cause ozone holes in the ozone layer. Ozone hole refer to depletion of ozone molecules in the ozone layer due to the reaction of CFCs. The holes in the ozone layer appear elsewhere and not where these chemicals are used.

(ii) More ultraviolet radiations reach the earth through the ozone holes and the reflected radiations from the earth are absorbed by CO2 water vapour, etc.

The trapped radiations release more and more heat resulting in the phenomenon of Global Warming. This effect is also known as Green House Effect.

Global environment damage affects quality of environment over a much larger area and is not localized to the area where the damage is initiated. Global warming will cause ill effects and are not confined to the area causing the damage. It causes wide range of effects like melting of glaciers, polar caps, rise in water level of sea and flooding of coastal plains, etc.

INTEXT QUESTIONS 32.1

1. Define environment.

The air, water, earth and living beings in a joint form is called environment.

2. What are the two components of environment?

There are two components of environment namely biotic and abiotic.

3. List three biotic components?

Living organisms such as plants, animals, microbes, etc.

4. How do CFCs affect the ozone layer?

Causes holes in the ozone layer.

5. What are the different segments of environment?

Atmosphere, biosphere, hydrosphere and lithosphere.

32.2 POLLUTION

In ancient times human settlements began and flourished along riverbanks as rivers provided them basic facilities. Growth of population forced people to move to other places.

They started utilising natural resources such as trees and soil(mud) to build shelters. More waste material started collecting at places they inhabited.

Humans themselves created conditions for disposal of waste (sanitation).

Humans then started industries to manufacture goods for their own comforts.

Pesticides and chemical fertilisers were manufactured to grow more food for the growing demand by population.

Industries also generated wastes, which ultimately finds its way to water sources.

Pesticides and chemicals were washed into natural water bodies such as sea, river, lakes and ponds and affected the aquatic organisms.

Supply of potable (safe for drinking) water diminished. All this badly affects life of organism including humans. All such waste generated through human activities and spoiling the natural environment is termed as pollutants.

Damaging the natural environment by pollutants is termed as pollution.

Pollution refers to deterioration or unclean objectionable conditions in the quality of natural resources such as air, water and soil because of the action or presence of unwanted substances beyond a certain limit.

INTEXT QUESTIONS 32.2

32.3 POLLUTANTS

Pollutants are the substances or effect introduced into the environment in significant amounts in solid, semi solid, liquid gas or sub molecular particle form which has a detrimental (bad) effect on the environment.

The pollutants may be classified in the following ways

https://share.google/aimode/Jj5LorwzUVxQFcyed

Natural air pollutants are substances released into the atmosphere by natural processes such as volcanic eruptions, forest fires, dust storms, oceanic activity, and biological decay. These include gases like CO₂, CH₄, SO₂, and particulates such as ash, soot, pollen, and radon.

🌍 Major Natural Air Pollutants

1. Greenhouse gases

Carbon dioxide (CO₂): Released from volcanic eruptions, oceanic processes, and respiration.
Methane (CH₄): Produced by wetlands, termites, and digestive processes in animals.
Nitrous oxide (N₂O): Emitted from soil microbial activity and oceans.

2. Volcanic emissions

Sulphur dioxide (SO₂): Major volcanic gas contributing to acid rain and aerosols.
Ash and particulates: Cause short-term cooling by blocking sunlight.
Hydrogen chloride (HCl) and other halogens.

3. Wildfire pollutants

Carbon monoxide (CO), CO₂, methane, and VOCs.
Soot and smoke particles that reduce visibility and harm respiratory health.

4. Dust and sand storms

Large amounts of particulate matter (PM10, PM2.5) lifted into the atmosphere.
Can travel across continents, affecting air quality far from the source.

5. Biological pollutants

Pollen grains from plants.
Spores, bacteria, and viruses naturally dispersed in the air.
Marsh gases (methane from wetlands).

6. Oceanic sources

Sea spray aerosols containing salts.
Dimethyl sulfide (DMS) from phytoplankton, which contributes to cloud formation.

7. Radioactive pollutants

Radon gas: Released from the Earth’s crust due to radioactive decay of radium.
Accumulates in enclosed spaces and is a major natural cause of lung cancer.

📊 Summary Table

Category	Examples	Source
Greenhouse gases	CO₂, CH₄, N₂O	Volcanoes, oceans, wetlands, animals
Volcanic emissions	SO₂, ash, HCl	Volcanic eruptions
Wildfire pollutants	CO, CO₂, soot	Forest fires
Dust storms	PM10, PM2.5	Arid regions, deserts
Biological pollutants	Pollen, spores, marsh gases	Plants, wetlands
Oceanic sources	Sea salt, DMS	Oceans, phytoplankton
Radioactive pollutants	Radon	Earth’s crust decay

🔹 Major Anthropogenic Air Pollutants

1. Carbon monoxide

Produced by incomplete combustion of fossil fuels in vehicles and industries.
Highly toxic, reduces oxygen delivery in the body.

2. Sulphur oxides

Emitted from burning coal and oil in power plants.
Contribute to acid rain and respiratory problems.

3. Nitrogen oxides

Released from vehicle exhausts and industrial processes.
Precursor to smog and acid rain.

4. Particulate matter

Dust, soot, smoke, and fine particles from construction, mining, and combustion.
PM2.5 and PM10 are especially harmful to lungs.

5. Volatile organic compounds

From paints, solvents, plastics, and fuel vapors.
React with NOx to form photochemical smog.

6. Heavy metals

Lead, mercury, cadmium from industrial emissions and waste incineration.
Toxic to nervous system and ecosystems.

7. Chlorofluorocarbons (CFCs)

Released from refrigerants and aerosols.
Cause ozone layer depletion.

📊 Natural vs Anthropogenic Pollutants

Category	Examples	Source
Natural pollutants	CO₂, CH₄, SO₂, ash, pollen, radon	Volcanoes, forest fires, oceans, wetlands
Anthropogenic pollutants	CO, NOx, SO₂, PM2.5, VOCs, CFCs	Vehicles, industries, fossil fuel burning, chemicals

⚠️ Key Insight

Natural pollutants are often episodic (volcanoes, wildfires), while anthropogenic pollutants are continuous and cumulative, making them more dangerous for long-term air quality.
In urban areas like Chennai, anthropogenic pollutants (vehicle exhaust, industrial emissions, construction dust) dominate over natural sources.

Air pollutants are broadly classified into primary pollutants (directly emitted from sources like vehicles, industries, or natural events) and secondary pollutants (formed in the atmosphere through chemical reactions, such as smog or acid rain). They can also be categorized by their physical state (gaseous vs particulate) and source (natural vs anthropogenic).

🔹 Classification of Air Pollutants

1. Primary pollutants

Emitted directly from natural or human activities.
Examples:
- Carbon oxides (CO, CO₂)
- Nitrogen oxides (NO, NO₂)
- Sulphur oxides (SO₂, SO₃)
- Hydrocarbons (CH₄, VOCs)
- Particulate matter (dust, smoke, ash)

2. Secondary pollutants

Formed in the atmosphere by chemical reactions between primary pollutants and natural constituents.
Examples:
- Ozone (O₃)
- Sulphuric acid (H₂SO₄)
- Nitric acid (HNO₃)
- Photochemical smog

🔹 Other Classification Methods

By State of Matter

Gaseous pollutants: CO₂, NO₂, SO₂, ozone.
Particulate pollutants: Dust, soot, smoke, fly ash, pollen, radioactive particles.

By Source

Natural sources: Volcanic eruptions, forest fires, dust storms, methane from cattle, radon gas.
Anthropogenic sources: Vehicle emissions, industrial discharges, burning of fossil fuels, plastic burning, deforestation.

📊 Comparison Table

Category	Definition	Examples
Primary pollutants	Directly emitted into atmosphere	CO, SO₂, NO, hydrocarbons, dust
Secondary pollutants	Formed by reactions in atmosphere	Ozone, H₂SO₄, HNO₃, smog
Gaseous pollutants	Exist in gas state	CO₂, NO₂, SO₂
Particulate pollutants	Solid/liquid suspended particles	Dust, soot, ash, pollen
Natural sources	Originates from environment	Volcanoes, forest fires, radon
Anthropogenic sources	Human activities	Vehicles, industries, plastics

Water pollutants are classified into seven major categories: organic pollutants, pathogens, nutrients, suspended solids, inorganic pollutants, thermal pollution, and radioactive pollutants. Each category affects water quality differently, with impacts ranging from oxygen depletion to toxic contamination.

🔹 Classification of Water Pollutants

1. Organic pollutants

Oxygen-demanding wastes: Sewage, food processing waste, paper mills, tanneries.
Synthetic organics: Pesticides, detergents, plastics, pharmaceuticals.
Oil spills: Reduce dissolved oxygen and harm aquatic life.

2. Pathogens

Disease-causing microorganisms such as bacteria, viruses, protozoa, and helminths.
Sources: Human and animal waste.
Effects: Cholera, dysentery, typhoid.

3. Nutrients

Nitrogen and phosphorus from fertilizers and sewage.
Cause eutrophication, leading to algal blooms and oxygen depletion.

4. Suspended solids

Soil, silt, and sediments from erosion, construction, and mining.
Increase turbidity, block sunlight, and smother aquatic habitats.

5. Inorganic pollutants

Salts, heavy metals (lead, mercury, cadmium, arsenic).
Toxic to aquatic organisms and humans.

6. Thermal pollution

Heated water discharged from power plants and industries.
Raises water temperature, reducing dissolved oxygen and stressing aquatic life.

7. Radioactive pollutants

Radionuclides from mining, nuclear plants, and medical use.
Long-term contamination, bioaccumulation, and cancer risks.

📊 Summary Table

Category	Examples	Source	Impact
Organic pollutants	Sewage, pesticides, oil	Domestic waste, industries	Oxygen depletion, toxicity
Pathogens	Bacteria, viruses	Sewage, animal waste	Waterborne diseases
Nutrients	N, P compounds	Fertilizers, sewage	Algal blooms, eutrophication
Suspended solids	Silt, clay, sediments	Erosion, mining	Turbidity, habitat loss
Inorganic pollutants	Heavy metals, salts	Industry, mining	Toxicity, bioaccumulation
Thermal pollution	Heated effluents	Power plants	Reduced oxygen, fish stress
Radioactive pollutants	Radon, uranium	Nuclear plants, mining	Cancer, long-term contamination

Soil pollutants are substances that degrade soil quality, reduce fertility, and harm ecosystems. They can be classified based on their origin, chemical nature, and impact.

🔹 Classification of Soil Pollutants

1. Organic pollutants

Examples: Pesticides, herbicides, insecticides, plastics, petroleum hydrocarbons.
Source: Agricultural practices, industrial waste, oil spills.
Impact: Toxic to soil microbes, reduce fertility, bioaccumulate in food chains.

2. Inorganic pollutants

Examples: Heavy metals (lead, mercury, cadmium, arsenic), salts, acids.
Source: Mining, smelting, industrial effluents, chemical fertilizers.
Impact: Persistent contamination, toxic to plants and humans.

3. Radioactive pollutants

Examples: Uranium, radium, cesium, strontium isotopes.
Source: Nuclear power plants, mining, improper disposal of radioactive waste.
Impact: Long-term soil contamination, cancer risk through bioaccumulation.

4. Biological pollutants

Examples: Pathogens (bacteria, viruses, parasites), invasive species.
Source: Sewage sludge, animal waste, improper disposal of biomedical waste.
Impact: Spread of diseases, disruption of soil ecology.

5. Industrial pollutants

Examples: Fly ash, slag, chemical residues, dyes.
Source: Factories, tanneries, textile industries, paper mills.
Impact: Alters soil pH, reduces fertility, contaminates groundwater.

6. Agricultural pollutants

Examples: Excess fertilizers, pesticides, herbicides.
Source: Intensive farming practices.
Impact: Soil acidification, nutrient imbalance, groundwater pollution.

7. Urban pollutants

Examples: Plastic waste, construction debris, sewage sludge.
Source: Cities, landfills, improper waste disposal.
Impact: Loss of soil structure, reduced permeability, toxic leachates.

📊 Summary Table

Category	Examples	Source	Impact
Organic	Pesticides, plastics	Agriculture, oil spills	Toxicity, bioaccumulation
Inorganic	Heavy metals, salts	Mining, fertilizers	Persistent contamination
Radioactive	Uranium, cesium	Nuclear waste	Long-term toxicity
Biological	Pathogens	Sewage, animal waste	Disease spread
Industrial	Fly ash, dyes	Factories	Soil pH change
Agricultural	Fertilizers, pesticides	Farming	Acidification, imbalance
Urban	Plastics, debris	Landfills, cities	Toxic leachates

⚠️ Local Context (Tamil Nadu)

Industrial belts (Ranipet, Vellore): Heavy metal contamination from tanneries.
Agricultural regions: Excess fertilizer and pesticide use leading to soil degradation.
Urban Chennai: Plastic and construction debris in landfills affecting soil quality.

Note:

A tannery is an industrial facility where animal hides and skins are processed into leather through chemical and mechanical treatments. The process is called tanning, and it stabilizes the proteins in the hides so they don’t decompose, making them durable and flexible for use in shoes, bags, belts, upholstery, and other leather goods.

🔹 Key Features of Tannaries

1. Raw material

Cow, buffalo, goat, and sheep hides are the most common.
Skins are cleaned, soaked, and treated before tanning.

2. Tanning process

Vegetable tanning: Uses plant-based tannins (from bark, leaves).
Chrome tanning: Uses chromium salts, faster and widely used.
Other methods: Aldehyde tanning, synthetic tanning.

3. Pollutants

Solid waste: Fleshings, hair, trimmings.
Liquid waste: Effluents rich in chromium, sulphides, and organic matter.
Air emissions: Odors, volatile chemicals.

4. Products

Finished leather for footwear, garments, furniture, and accessories.

📊 Environmental Impact

Pollutant	Source	Impact
Chromium salts	Chrome tanning	Toxic to soil and water
Sulphides	Dehairing process	Harmful gases, water contamination
Organic waste	Fleshings, trimmings	Odor, microbial growth
Effluents	Wastewater	Groundwater pollution

32.3.1 Natural Pollutants

There can be several natural sources which are the cause of pollution. Some of them are listed below :

(i) Fires in forests may be caused when lightning strikes the trees. Burning of tree produces a lot of CO2 which is released to the atmosphere.

(ii) Soil erosion increases suspended particulate matter and dust in air. These may even enter water bodies as they are washed down by rain or natural waterfalls.

(iii) Volcanic eruptions also add pollutants like SO2 and solid particles to the environment.

(iv) Volatile organic compounds from leaves, trees and dead animals naturally enter the atmosphere.

(v) Natural radioactivity and the other natural pollutants have been entering the environment since ages. (But the low level of pollution has rarely endangered lives of organisms).

32.3.2 Anthropogenic Pollutants

Increased human activities releases a large amount of pollutants to the environment and poses a threat to the human life. Pollutants added to the environment through human activities are termed anthropogenic pollutants. These are of two kinds.

(i) Primary pollutants: Primary pollutants are added directly in a harmful form to the atmosphere. eg CO2 and CO from burning of fossil fuel; SO2 and oxides of nitrogen from vehicular combustion, thermal power stations, etc.

(ii) Secondary Pollutants: Secondary pollutants are the products of reaction between the primary pollutants and normal environmental constituents.

2SO2 + O2 ⎯⎯→ 2SO3

Thus, SO2 a primary pollutant which reacts with oxygen of air to give SO3.

Further, SO3 reacts with water-vapour present in the atmosphere and forms H2SO4. Thus, SO3 and H2SO4 are secondary pollutants.

SO3 + H2O ⎯⎯→ H2SO4

2NO + O2 ⎯⎯→ 2NO2

Nitric oxide (NO), a primary pollutant reacts with oxygen to give NO2 which is a secondary pollutant.

Depending on the sources. anthropogenic pollutants may be classified further into

(i) Industrial Pollutants

(ii) Domestic Pollutants

(i) Industrial Pollutants: Paper, textile industries, tanneries and distilleries dispose various effluents like oil, grease, plastic and metallic wastes into the environment.

(ii) Domestic Pollutants: Detergents, fluoride toothpastes, edible colours, food flavouring agents, polythene bags and wrappers find their way into the environment as pollutants. Methane is produced in cattle stomach and in stagnant paddy fields is also a domestic pollutant.

INTEXT QUESTIONS 32.3

1. Define a pollutant.

Any substance which is present in its excess concentration such as CO2, CO,SO2.

2. Name two sources of natural pollution.

Volcanic eruptions and run-off from surface mines.

3. Define a secondary pollutant.

Secondary pollutants are the products of reaction between the primary pollutant and the normal environmental constituents.

4. What do you mean by environmental pollution?

Environmental pollution is the deterioration or unclean objectionable conditions in the quality of natural resources such as air water and soil because of the action or presence of unwanted substances in undesirable concentration.

32.4 SOURCES OF POLLUTANTS

Many of the pollutants in our environment have natural as well as human related origins. For example, the natural origin of pollutants includes the release of Sulphur dioxide (SO2) from volcanic eruptions, erosion of soil by wind and water, dissolved minerals carried on to rivers and ocean by surface run off, etc.

The sources of pollutants are also classified:

(i) Stationary and

(ii) Mobile sources

Stationary Sources: The pollutants released from a fixed location or a well-defined area is known as stationary source. e.g. smokestacks of power plants, smelters, surface mines, etc.

Mobile Sources: The pollutants released from diffused sources or the sources that move from place to place is termed as a mobile source. e.g. automobiles, buses, aircrafts, ships, trains, etc.

The various pollutants of water, their sources and effects are given in Table 32.1

Here’s a clear table summarizing the major air pollutants, their sources, harmful effects, and control measures — useful for quick study or reference.

Major Air Pollutants Overview

Pollutant	Sources	Effects	Control Measures
Particulate Matter (PM2.5 & PM10)	Vehicle exhaust, industrial emissions, construction dust, stubble burning, forest fires	Respiratory diseases (asthma, bronchitis), lung cancer, heart disease, premature death	Use cleaner fuels, control construction dust, promote public transport, install air filters
Carbon Monoxide (CO)	Incomplete combustion of fuels (vehicles, biomass burning, faulty stoves)	Reduces oxygen transport in blood, causes headaches, dizziness, nausea, can be fatal	Ensure proper combustion, catalytic converters in vehicles, avoid indoor biomass burning
Sulphur Dioxide (SO₂)	Burning coal/oil in power plants, oil refineries, smelting, volcanoes	Irritates eyes, throat, lungs; causes asthma, bronchitis; forms acid rain damaging crops & forests	Switch to low-sulfur fuels, flue-gas desulfurization, renewable energy adoption
Nitrogen Oxides (NOₓ)	Vehicle emissions, power plants, industrial processes, lightning	Respiratory problems, reduced lung function, contributes to smog & acid rain	Use catalytic converters, reduce fossil fuel use, stricter emission standards
Ground-Level Ozone (O₃)	Formed by reaction of NOₓ & volatile organic compounds (VOCs) under sunlight	Causes chest pain, coughing, worsens asthma, damages crops	Reduce NOₓ & VOC emissions, promote cleaner transport, regulate industrial emissions
Lead (Pb)	Leaded gasoline (historically), battery manufacturing, metal smelting	Neurological damage, developmental issues in children, kidney damage	Ban leaded fuels, enforce industrial regulations, proper waste disposal
Carbon Dioxide (CO₂) & Methane (CH₄)	Fossil fuel burning, agriculture, landfills	Global warming, climate change, sea-level rise, extreme weather	Renewable energy, afforestation, energy efficiency, waste management

Key Insights

PM2.5 is the deadliest pollutant because it penetrates deep into lungs and bloodstream.
SO₂ and NOₓ are major contributors to acid rain.
Ground-level ozone is harmful unlike stratospheric ozone, which protects us from UV rays.
Control measures focus on clean energy, stricter regulations, and public awareness.

Here’s a structured table summarizing major water pollutants, their sources, effects, and control measures — perfect for quick study or reference.

Major Water Pollutants Overview

Pollutant	Sources	Effects	Control Measures
Pathogens	Sewage, animal waste, untreated wastewater	Spread of diseases (cholera, typhoid, dysentery), unsafe drinking water	Proper sewage treatment, chlorination, safe sanitation practices
Organic Waste	Food waste, agricultural runoff, paper mills	Depletes dissolved oxygen, harms aquatic life, foul odor	Aeration, composting, wastewater treatment
Nutrients (Nitrates & Phosphates)	Fertilizers, detergents, sewage	Eutrophication, algal blooms, fish kills	Controlled fertilizer use, buffer strips, wastewater treatment
Heavy Metals (Lead, Mercury, Cadmium)	Industrial discharge, mining, battery waste	Toxic to humans and aquatic life, neurological damage, bioaccumulation	Strict industrial regulation, safe disposal, phytoremediation
Oil & Grease	Oil spills, industrial effluents, shipping	Coats aquatic surfaces, suffocates marine life, contaminates drinking water	Oil spill containment, bioremediation, stricter shipping regulations
Plastics & Microplastics	Improper waste disposal, packaging, fishing nets	Ingestion by aquatic organisms, disrupts ecosystems, enters food chain	Ban single-use plastics, recycling, cleanup drives
Thermal Pollution	Power plants, industrial cooling processes	Alters water temperature, reduces oxygen, affects aquatic biodiversity	Cooling towers, discharge regulation, renewable energy use
Radioactive Substances	Nuclear plants, improper disposal of radioactive waste	Genetic mutations, cancer risk, long-term contamination	Safe disposal, strict monitoring, alternative energy sources

Key Insights

Nutrient pollution is the leading cause of eutrophication in lakes and rivers.
Heavy metals and radioactive substances persist for decades, making them especially dangerous.
Plastic pollution is now found even in drinking water and marine food chains.
Effective control requires wastewater treatment, stricter regulations, and public awareness.

Here’s a clear and organized table summarizing major soil pollutants, their sources, effects, and control measures — ideal for study or quick reference.

Major Soil Pollutants Overview

Pollutant	Sources	Effects	Control Measures
Pesticides & Fertilizers	Agricultural runoff, excessive chemical use	Soil degradation, reduced fertility, contamination of groundwater, harm to soil organisms	Organic farming, controlled fertilizer use, integrated pest management
Heavy Metals (Lead, Mercury, Cadmium)	Industrial waste, mining, battery disposal	Toxic to plants, bioaccumulation in food chain, neurological and kidney damage in humans	Safe disposal, phytoremediation, stricter industrial regulations
Plastics & Polythene	Improper waste disposal, packaging materials	Non-biodegradable, reduces soil aeration, harms soil microbes	Ban single-use plastics, recycling, proper waste management
Industrial Waste	Factories, chemical plants, tanneries	Alters soil chemistry, toxic to crops, contaminates groundwater	Waste treatment plants, eco-friendly technologies, strict regulation
Radioactive Substances	Nuclear plants, improper disposal of radioactive waste	Long-term contamination, genetic mutations, cancer risk	Safe disposal, monitoring, alternative energy sources
Biological Waste	Sewage sludge, animal waste, food waste	Spread of pathogens, foul odor, reduced soil quality	Composting, biogas production, proper sanitation
Oil & Hydrocarbons	Oil spills, leakage from machinery, petroleum industries	Reduces soil fertility, toxic to plants and microbes	Bioremediation, containment, strict monitoring

Key Insights

Pesticides and fertilizers are the most widespread soil pollutants due to intensive farming.
Heavy metals and radioactive substances persist for decades, making them especially dangerous.
Plastic pollution in soil is rising rapidly, affecting soil health and crop productivity.
Effective control requires sustainable agriculture, strict industrial regulation, and public awareness.

The general effects of pollutants are produced due to interactions of pollutants among themselves.

Contamination

Contaminations refer to the mere presence of undesirable materials to a medium like air, water, soil, etc. making it unfit for a particular use. For example, contamination of air by hazardous exhaust from automobiles. It becomes a pollutant if its concentration exceeds the level which can cause harmful effect.

INTEXT QUESTIONS 32.4

32.5 AIR POLLUTION

You have just learnt how nature has its own means of using up and getting back its components such as CO2, O2 and N2. If the balance of CO2, O2 or N2 is disturbed by human activity then it will have adverse effect on life on the earth.

Now you know why environmentalists are deeply concerned about environmental pollution,

tree plantations and afforestation.

Undesirable changes have occurred in the physical and chemical constituents of air due to human activities. Undesirable change in the atmosphere is air pollution.

Pollutant gases such as SO2 oxides of nitrogen, CO and excessive amount of CO2 have been added to the atmosphere. Air pollutant may be classified as particulate matter, liquid droplets and gaseous pollutants (Fig 32.2) :

32.5.1 Particulate Pollutants

Particulate pollutants such as soot and fly ash are released by various industries as by products of industrial processes. They are blown away by wind when they come out of the chimneys and other outlets of industries and mix with air.

Suspended particulate matter is also emitted by exhaust of polluting diesel vehicles and ill managed coal fired power plants. In nature, forest fires, wind erosion and volcanic eruptions add suspended particulate matter into air.

Examples of particulate pollutants are soot, flyash from thermal power plants, cement dust,

petrocoke from petroleum refineries. Some of the particulate pollutants are discussed in detail below:

Fluoride: Aluminium, steel and electrochemical plants, blast furnaces, brick kilns, coal combustion, tile and glass etching factories add fluoride particles which settle on vegetation. They burn tips of leaves and when cattle eat the vegetation they suffer from fluorosis resulting in loss of teeth, weight and lameness.

Humans also suffer from fluorosis. Volcanoes also release fluorides which form gaseous as

well as particulate pollutant.

Lead: Lead particles come into air from automobile exhausts. Lead is used as an antiknock agent in automobile gasoline which contains tetraethyl lead. Paint, ceramic and pesticide industries also add lead particles to the atmosphere.

Manufacture of lead storage batteries and recycling of discarded batteries add to lead pollution. Lead interferes with development of red blood corpuscles and causes anaemia (lack of haemoglobin - the oxygen carrying pigment of blood).

Lead is a cumulative poison and prolonged exposure even in low concentration may damage kidneys and liver.

Dust: Particulate matter less than 10 microns in size is dust. It reaches lungs, deposits along the respiratory tract and causes asthma or even lung cancer. Dust from stone crushers is another example of particular pollutant.

Sodium chloride: Sodium chloride is used to remove snow in winter and remains in the environment. Some sodium chloride is also added to the environment when waves of the sea spray it. Excess sodium chloride has been found to cause defoliation (leaf falling), suppression of flowering and breaking of terminal shoots of apple.

Agricultural chemicals: Chemical insecticides, herbicides and other pesticides are known to have damaging effects on plants. They are toxic to animals and humans also. Residues of pesticides get suspended as particulate matter in air.

32.5.2 Hydrocarbons

Hydrocarbons which may be in the form of liquid droplets or gas pollute air. As liquid droplets they spill or are added through seepage of oil fields and natural gas leakage. Methane is emitted in the swamps and paddy fields by methanogenic bacteria. Methane (CH4) is also generated in stomachs of ruminant animals.

Incomplete combustion of fuels release 3, 4 benzopyrene which causes lung cancer.

Pesticides, paints and solvents also release hydrocarbons. Hydrocarbons are a source of photochemical smog.

32.5.3 Gaseous Pollutants

SO2, CO2, nitrogen oxides are commonly added to the air by human activities.

Excess of these have very serious damaging effects on the physical environment as well as on humans.

SO2 and H2S: These are released into atmosphere through smelting of ores containing sulphur, manufacture of H2SO4 petroleum refining, combustion of fossil

fuels, paper making, burning of sulphur containing refuse and in nature through

volcanic eruptions. Plants exposed to SO2 and H2S show defoliation (leaves falling

off) and reduced growth.

In humans, SO2 pollution causes headache, vomiting, irritation of eye and respiratory passages. SO2 reacts with water to form H2SO4 which is washed down as acid rain about which you shall study later in the chapter.

Nitrogen Oxides: Anaerobic breakdown of nitrogenous compounds by bacteria is the natural source of nitrogen oxides. Burning fossil fuel also releases them.

Power generators, automobile exhausts, explosives and nitrogenous fertilizer industries and the other anthropogenic sources produce nitrogen oxides.

NO2: causes early dropping off of leaves and fruits in plants. Nitrogen oxides are one source of photochemical smog, acid deposition and greenhouse effect.

CO2 and CO : Combustion of oil, gas, coal and wood releases CO2 in the atmosphere. CO is released chiefly from gasoline engines and burning of coal in

defective furnaces. Motor vehicles with internal combustion engines emit high

levels of CO and hydrocarbons. Excess of CO2 can cause global warming, CO

causes photochemical smog and has a fatal effect when inhaled by humans.

CO poisoning: CO has a high affinity for haemoglobin. It combines with the blood pigment haemoglobin to form carboxyhaemoglobin. The normal function of haemoglobin is to carry O2. But CO combines with haemoglobin about two hundred times faster than O2. Tissues do not get oxygen and die due to lack of oxygen.

Carboxy haemoglobin is dark red in colour, the victims of CO poisoning have dark red lips. Mild CO poisoning causes lung disorders like bronchitis and emphysema. CO from cigarette smoke makes haemoglobin nonfunctional in smokers.

Photochemical oxidants: Primary pollutants such as nitrogen oxides and hydrocarbons mix in the atmosphere and form secondary pollutants like peroxyacetyl nitrate (PAN) and ozone, under the influence of UV radiation from the sun. Both PAN and O3 form photochemical smog. PAN and O3 are toxic to plants.

In humans they cause irritation of eyes coughing, headache, dry throat, respiratory problems and haemorrhage.

Tobacco smoke: Smoke from burning cigarettes or bidis contains nicotine, aromatic hydrocarbons and tar. These cause problems of blood pressure and heart, windpipe and lungs in the smoker as well as those around the smoker.

Cigarette smoke is also carcinogenic. The various human and natural activities which

introduce air pollutants into the atmosphere are summarized in Table 32.2

INTEXT QUESTIONS 32.5

1. What is atmospheric pollution?

undesirable level of undesirable and harmful substances in the atmosphere

2. Name two particulate pollutants.

soot, fluoride, Pb dust, NaCl (any two)

3. Name two gaseous pollutants?

SO2, CO2, CO, NH3, H2S (any two)

4. Name one source which causes pollution due to methane.

methanogenic bacteria, ruminant stomach, fermentation in waterlogged paddy fields (any one).

5. Name two air pollutants which form photochemical smog.

PAN and O3

32.6 EFFECTS OF EXCESSIVE ATMOSPHERIC POLLUTANTS ON NATURE (OUTDOOR

POLLUTION)

You are now familiar with the various atmospheric pollutants. Most of these are products of fuel combustion. These pollutants have been released into atmosphere ever since human first started burning wood and coal. Later on, pollutants are being released into air due to increased industrial activity. The nature has not been able to remove all these pollutants because much more pollutants are added than the nature can handle to maintain the balance. Therefore, pollutants have now accumulated in the atmosphere to a proportion whereby atmospheric composition of air has been significantly altered. It is the causes of physical

phenomena such as photochemical smog, acid rain, ozone depletion, greenhouse

effect and global warming. These are damaging to plants, animals and humans.

The figure Fig. 32.3 shows the four major effects of atmospheric pollutants. In the diagram, arrows from the pollutant depicts its involvement in the physical phenomenon.

The sources of the pollutants are depicted below the names of the pollutants. The four major phenomena are subsequently discussed one by one. They are temperature inversion, photochemical smog, acid rain, greenhouse effect and ozone layer (shield) depletion.

INTEXT QUESTIONS 32.6

32.7 TEMPERATURE INVERSION AND PHOTOCHEMICAL SMOG

Pollutants like sulphur dioxide which is released while burning sulphur containing fuels (fossil fuels) and particulate matter like soot present in stagnant air masses, get modified in sunlight and form a sheet called photochemical smog.

Smog is a combination of fog, smoke and fumes released by mills and factories, homes and automobiles.

When sunlight falls on stagnant air under low humid conditions in the presence of pollutants such as SO2 soot, nitrogen oxides and hydrocarbons, photochemical smog is formed (photochemical: chemical reactions in the presence of light).

Smog stays close to the ground and reduces visibility and causes irritation.

Photochemical smog is also called PAN smog due to the formation of peroxyacetyl nitrate or PAN and ozone which are formed from hydrocarbons and nitrogen oxides in the presence of solar radiation. PAN and ozone are called photochemical oxidants. Both of these are toxic irritants to human lungs.

Smog formation is accompanied by Temperature inversion or Thermal inversion, Temperature inversion causes smog to settle and remain near the ground till wind sweeps it away. Normally, warm air rises up into atmosphere. When a layer of cool air at the ground level is held there by an overlying layer of warm stagnant air. It is called temperature or thermal inversion (Fig.32.4).

Exposure to smog causes respiratory problems, bronchitis, sore throat, cold, headache and irritation to eyes (red shot eyes). Smog also damages crops and reduces crop yield.

Atmospheric pollutants are broadly classified into primary (directly emitted) and secondary (formed by reactions in the atmosphere) and further categorized by their physical state (gaseous vs particulate) and source (natural vs anthropogenic). This classification helps in identifying their origin, behavior, and control strategies.

🔹 Classification of Atmospheric Pollutants

1. By Origin

Primary pollutants: Directly emitted from sources.
- Examples: Carbon monoxide (CO) from vehicles, sulfur dioxide (SO₂) from power plants, nitrogen oxides (NOx) from combustion, particulate matter (PM), hydrocarbons.
Secondary pollutants: Formed in the atmosphere through chemical reactions between primary pollutants.
- Examples: Ozone (O₃), peroxyacetyl nitrate (PAN), acid rain (H₂SO₄, HNO₃), photochemical smog.

2. By Physical State

Gaseous pollutants: CO₂, SO₂, NO₂, ozone, volatile organic compounds (VOCs).
Particulate pollutants: Dust, smoke, soot, fly ash, aerosols, pollen, radioactive particles.

3. By Source

Natural sources:
- Volcanic eruptions (SO₂, ash), forest fires (CO, smoke), dust storms, pollen, methane from cattle, radon gas from Earth’s crust.
Anthropogenic sources:
- Industrial emissions, vehicle exhaust, burning of fossil fuels, agricultural activities, waste incineration, chemical industries.

4. By Chemical Composition

Oxides of carbon: CO, CO₂
Oxides of nitrogen: NO, NO₂
Oxides of sulfur: SO₂, SO₃
Hydrocarbons: Methane, benzene
Other toxic substances: Lead, arsenic, ammonia, polychlorinated biphenyls (PCBs).

📊 Comparison Table

Category	Examples	Key Effects
Primary pollutants	CO, SO₂, NOx, hydrocarbons, PM	Respiratory illness, acid rain precursors
Secondary pollutants	Ozone, PAN, H₂SO₄, HNO₃	Smog, acid rain, ecosystem damage
Gaseous pollutants	CO₂, NO₂, SO₂, VOCs	Climate change, lung irritation
Particulate pollutants	Dust, soot, aerosols, pollen	Asthma, reduced visibility
Natural sources	Volcanoes, wildfires, radon	Episodic pollution events
Anthropogenic sources	Vehicles, industries, agriculture	Persistent urban pollution

⚠️ Risks & Impacts

Human health: Respiratory diseases, cardiovascular problems, cancers.
Environment: Acid rain, ozone depletion, climate change, reduced biodiversity.
Economic: Crop damage, reduced productivity, healthcare costs.

INTEXT QUESTIONS 32.7

32.8 ACID RAIN

Coal and oil burned by power plants and other industries release SO2 into air because coal and oil contain small amount of sulphur. Automobile exhausts add SO2 and nitrogen oxides to the air. Both SO2 and nitrogen oxides are converted into acids HNO3 and H2SO4 when they combine with oxygen and water vapour in the atmosphere as per the following photo chemical reactions.

2SO2 + O2 + 2H2O → 2H2SO4

4NO2 + O2 + 2H2O → 4HNO3

This reaction is promoted by O3 in smog. The acids, so formed are washed down from air to earth during rain or snow fall. It is called acid rain or acid snow. The acids react with minerals present in soil to form sulphates and nitrates due to acid rain.

Rainwater even in its purest form is slightly acidic with pH 5.6 due to dissolved CO2. But areas near coal and oil burning industries and where motor vehicles ply in large numbers, pH goes down to 2 and rain becomes strongly acidic. Mountain foothills are the worst affected. There is moisture laden air rises to higher altitudes it condenses to fall as rain or snow, dropping its load of pollutants. In spring. snow melts and adds pollutants to lakes and other water bodies.

When the dissolved pollutants drop as rain or snow (wet deposition) it is termed acid precipitation. Deposition of dry gases and salts is dry deposition. Acid rain spreads over areas of several hundreds to several thousand kilometers.

32.8.1 Effects of Acid Rain

Some of the effects of acid rain are listed below:

(1) Excessive acid concentrations are phytotoxic (toxic to plants). There has been widespread death of trees in forests due to acid rain.

(2) Sea waters are rich in minerals and have great buffering capacity. But buffering capacity of freshwater bodies is low and acid deposits have a toxic effect on the freshwater ecosystems.

(3) Mature (capable of reproduction) fish survives in acid rain fed water bodies but fails to reproduce. So there are no young fish in such waters.

(4) Exposed surfaces of buildings, statues get corroded. Limestone or marble (CaCO3) structures are specially damaged (Fig. 32.5).

The chemical reaction is like CaCO3 + H2SO4 → CaSO4 + CO2 + H2O.

The sulphates are leached out by rain water.

(5) Acidic sulphate when present in the atmosphere causes laziness. Acidic mist falling on the ground reduces visibility.

Fig. 32.5 : A Stone statue showing corrosive effects of Acid Rain

32.9 GREEN HOUSE EFFECT AND GLOBAL WARMING

The literal meaning and function of green house is to trap the heat. You must have seen delicate plants being grown in a glass chamber which is comparatively warmer inside than outside. Glass permits solar radiations to come in but restricts the outward movement of heat. The radiations get trapped inside the glass chamber and raises the temperature.

Gases such as CO2, NO2, CFCs (chloro fluorocarbons) allow sun rays to pass through them but then absorb and reradiate the heat back towards the earth.

These are therefore termed as greenhouse gases.

32.9.1 Greenhouse Gases

The common green house gases and their sources of pollution are listed below:

(1) CO2 - from fossil fuel burning.

(2) NO2 - from fertilizer plants, automobile exhaust use and animal waste.

(3) CH4 - from bacterial decomposition, biogas, flooded rice fields.

(4) CFCs - from freon, (a refrigerant), areosol sprays.

(5) HALONS (halocarbons) - from fire extinguishers.

32.9.2 How Does Earth’s Atmosphere Trap Heat?

Radiations (ultra violet) from the sun penetrate the earth’s atmosphere and reach earth. The surface of earth partially absorbs the radiations. The rest is re-radiated as infrared radiation from the earth’s surface. In polluted air, molecules of CO2, CH4, CFCs, N2O, O3 and water vapours are present. These gases can absorb infrared radiations but cannot absorb the ultra violet radiations. Energy of these trapped radiations raise the temperature of earth and its atmosphere. Thus if proportion of green house gases increases in the atmosphere heat trapped by them will raise the temperature of the earth and will cause global warming.

Greenhouse effect leading to global warming shall have severe effects on rainfall, sea level, plant and animal growth..

Global warming is defined as the increase in the average global temperature of the atmosphere near earth’s surface.

(1) Rise in sea level: It is estimated that by the turn of the century a rise of 5°C in global temperature will be due to effect of greenhouse gases if not checked now. Polar ice caps would melt because of rise in temperature and add more water to sea. Moreover, water expands when it heats up. This will lead to rise of sea level. It will flood the low-lying coastal area and many cities will get submerged in water.

(2) Drought: A 3° C warming will result in 10% decrease in precipitation (rain fall) and this will decrease rain fall causing drought conditions.

(3) Effect on plant growth: Drought will reduce photosynthesis in plants and lead to reduced growth of plants.

(4) Effect on animals: Warmer conditions will encourage growth of pests.

(5) Water shortage: Increase in temperature will lead to increased evaporation leading to shortage of water for agricultural, municipal and industrial use.

(6) Climatic changes: It has great effect on climate changes. For example, spring now occurs about a week earlier than normal time.

(7) Increase in CO2: Warmer conditions accelerate microbial degradation of organic matter and add more CO2

(8) Day and Night temperature: Night temperatures have increased more than day temperature as greenhouse gases prevent heat from escaping at night.

(9) Formation of ozone hole:

The atmosphere has two layers, the stratosphere and troposphere. Stratosphere lies 15

km to 50 km above the surface of earth. The energy of the sun splits some molecular O2

in this layer to give individual (O) atoms which combine with intact molecular oxygen to

give O3. The layer of O3 forms a shield as it absorbs UV rays and prevent them from

striking the earth. If UV rays penetrate our atmosphere the life would not be possible as

organisms cannot tolerate heavy doses of UV radiation. Troposphere is the atmospheric

layer closest to the earth’s surface whose compostion you have already studied. Chloro

fluorocarbons and halons released into the atmosphere have destroyed the ozone shield

and an ozone hole has been detected at the South Pole of Antartic and North Pole of Arctic.

INTEXT QUESTIONS 32.9

32.10 DEPLETION OF OZONE LAYER

Ozone shield depletion is primarily caused due to the following reasons:

(a) Chlorofluorocarbons (CFCs) are the heat transfer agents used in refrigerators and air conditioners, and foaming agents in foam cups and cartons.

(b) Halons or halocarbons are anti fire agents used in fire extinguishers.

The ozone in the stratosphere is being depleted by the presence of mainly chlorofluorocarbons (CFCs) and halogen gas, particularly chlorine. The highly energetic ultra violet radiation splits up the CFCs, releasing chlorine. The released chlorine is responsible for convertion of the ozone into oxygen molecule consequently depletion of ozone layer occurs as per the following equations.

Cl + O3 → ClO + O2

ClO + O → Cl + O2

It is believed that one molecule of CFC is capable of destroying 1,00,000 ozone molecules in the stratosphere. The area where the ozone is completely destroyed is known as ozone hole. The first ozone hole was observed over Antarctic Ocean.

The important function of ozone layer in the stratosphere in to protect us from dangerous ultra violet (UV) radiations from the sun by absorbing it.

32.10.1 Effects of Ozone Depletion

Ozone layer depletion will allow more UV rays to enter the troposphere and will cause a series of harmful effects such as :

(1) Plants and animals living on the surface will start dying.

(2) UV radiation will fasten the formation of smog

(3) Temperature of the earth will increase leading to rise in sea level and flooding of low lying areas.

(4) More UV rays will directly fall on the skin of humans causing skin cancer.

(5) Leaves of plants will show chlorosis (loss of chlorophyll and yellowing),

INTEXT QUESTIONS 32.10

32.11 EFFECTS OF AIR POLLUTION ON HUMANS

Air is mobile and impact of air pollution on ecosystems is reduced as wind blows away pollutants. But when winds are calm, air pollution becomes not only damaging but life threatening.

The damaging effects of atmospheric pollution have been described along with the account on pollutants. Long term exposure to moderate pollution causes more discase and death. Some adverse effects of air pollution on humans are summarised in table 32.4.

Table 32.4 : Effects of air pollutants on humans

Disease / Discomfort Caused by

Emphysema. Bronchitis CO, SO2, PAN, O3

Eye irritation, headache SO2, PAN, O3

Silicosis. Asbestosis Suspended particulate matter like

silica, asbestos.

Coronary artery disease Tobacco smoke

Anemia, kidney, liver damage Pb

Fluorosis, Skin Cancer Fluorides

Poisoning death CO

INTEXT QUESTIONS 32.11

32.12 CONTROL OF AIR POLLUTION

The alarming rate at which the atmosphere is being polluted, soon there will be more ailing human beings than healthy. The need of the hour is to put a quick check to atmospheric pollution.

Since most of air pollutants are emitted during combustion of fossil fuels, there are two practical approaches for air pollution control which are discussed below:

(i) One approach is control undesirable changes in the air we breathe by observing the following precaution :

(a) Limiting pollutants into air by using sulphur-free oil and coal, using catalytic convertors in automobiles and avoiding burning of waste material.

(b) Taking stringent measures against release of emissions from industries.

(ii) The other approach is to use sources of energy other than fossil fuels such as wind, water, solar power, etc. Use bicycles and battery powered cars rather than vehicles with internal combustion engines. Service vehicles should use lead free petrol.

Above all, it is necessary to educate the general public. Air pollution should become

every human being’s concern. Only then will the air become more congenial to healthy living.

INTEXT QUESTIONS 32.12

1. What is smog?

fog + smoke = SMOG

2. Name two photochemical oxidants.

O3 and PAN

3. Name two gases which form acid rain.

SO2 and NO

4. Mention any four greenhouse gases.

CO2, NO2, CH4, CFC, Halons

5. What are the sources of freons and halons in air?

refrigerants, fire extinguishers

6. What effect does acid rain have on marble statues?

corrode them

7. Mention one measure to control air pollution.

reducing use of fuel which releases air pollutants and use clean renewable fuels. Educate everyone about dangers of pollution.

32.13 WATER POLLUTION – PARAMETERS

A large amount of water is discharged back after domestic and industrial usage.

This is contaminated with domestic waste and industrial effluents. When this contamination reaches beyond certain allowed concentrations, it is called pollution and the contaminants are called the pollutants. Water pollution may be defined as the contamination of streams, lakes, seas, underground water or oceans by substances, which are harmful for living beings. If the concentration of substances naturally present in water increases then also the water is said to be polluted.

Water pollution may be defined as the contamination of streams, lakes, seas,underground water or oceans by substances, which are harmful for living beings.

Industrialisation and population explosion are two important factors for water pollution.

Water may be called polluted when the following parameters stated below reach beyond a specified concentration in water.

(i) Physical parameters. Colour, odour, turbidity, taste, temperature and electrical conductivity constitute the physical parameters and are good indicators of contamination.

For instance, colour and turbidity are visible evidences of polluted water while an offensive odour or a bitter and difference than normal taste also makes water unfit for drinking.

(ii) Chemical parameters: These include the amount of carbonates, sulphates, chlorides, fluorides, nitrates, and metal ions. These chemicals form the total dissolved solids, present in water.

(iii) Biological parameters: The biological parameters include matter like algae, fungi, viruses, protozoa and bacteria. The life forms present in water are affected to a good extent by the presence of pollutants. The pollutants in water may cause a reduction in the population of both lower and higher plant and animal lives. Thus, the biological parameters give an indirect

indication of the amount of pollution in water.

INTEXT QUESTIONS 32.13

32.14 WATER POLLUTION – SOURCES

Water pollutants refer to the substances which are capable of making any physical, chemical or biological change in the water body. These have undesirable effect on living organisms. As mentioned earlier, the water used for domestic, agricultural and industrial purposes is discharged with some undesirable impurities in it. This contamination leads to the pollution of water, which is generally called the freshwater pollution. Fresh water pollution may be classified into two types: surface water pollution and ground water pollution.

32.14.1 Surface Water Pollution

When pollutants enter a stream, river or lake these gives rise to surface water pollution. The surface water pollution has a number of sources. These can categorized as:

• Point and Non-point Sources

• Natural and Anthropogenic Sources

(i) Point and Non-point Sources

The well-defined sources that emits pollutants or effluents directly into different water bodies of fresh water are called point sources. Domestic and industrial waste are examples of this type. The point sources of pollution can be effectively checked. On the other hand, the non-point sources of water pollution are scattered or spread over large areas. This type of sources deliver pollutants indirectly through environmental changes and account for majority of the contaminants in streams and lakes. For example, the contaminated water that runs off from agriculture farms, construction sites, abandoned mines, enters streams and lakes. It is quite

difficult to control non-point sources.

(ii) Natural and Anthropogenic Sources

As mentioned earlier, an increase in the concentration of naturally occurring substances is also termed pollution. The sources of such an increase are called natural sources.

Siltation (which includes soil, sand and mineral particles) is one such natural source. It is a common natural phenomenon, which occurs in most water bodies. Indiscriminate deforestation makes soil loose and flood waters bring silt from mountains into streams, rivers and lakes.

On the other hand, the human activities that result into the pollution of water are called anthropogenic or man-made sources of water pollution. For example, domestic (sewage and waste water), industrial and agricultural wastes that goes into the rivers, lakes, streams and seas are anthropogenic sources.

Certain materials that are leached from the land by run-off water and enter the various water bodies also belong to this category. The anthropogenic sources of water pollution are

shown in Fig. 32.7.

Fig. 32.7 : Anthropogenic Sources of water pollution

Schematic diagram illustrates water contamination due to natural sources (droughts and floods) and anthropogenic sources (industrial, agriculture, and urban activities), their pathways, receptors, and other types of pollution

32.14.2 Ground Water Pollution

When the polluted water seeps into the ground and enters an aquifer, it results into ground water pollution. The most of our villages and many townships, ground water is the only source of drinking water. Therefore, pollution of groundwater is a matter of serious concern. Groundwater gets polluted in a number of ways. The dumping of raw sewage on soil, seepage pits and septic tanks cause pollution of groundwater. Fig. 32.3. The porous layers of soil hold back solid particles while the liquid is allowed to pass through. The soluble pollutants are

able to mix with the groundwater. In addition to these, the excessive use of nitrogenous fertilizers and unchecked release of toxic wastes and even carcinogenic substances by industrial units many result in slow trickling down through the earth’s surface and mixing with the groundwater. This problem is very serious especially in areas where water table is high (i.e., where water is available near surface of earth).

The ground water can move over large distances by virtue of the large empty space available below the earth’s surface. This way if some impurities seep into the ground water at one point, they may be observed at a different point far removed from the point of source. In such a case it is difficult to estimate the source of water pollution. However, suspended impurities and bacterial contaminants are removed in the process of seepage by the soil acting as an

absorbent and filter, and water acting as a solvent.

Since the movement of groundwater through the porous rock is very slow, pollutants which get mixed with the groundwater are not readily diluted.

Furthermore, groundwater does not have access to air (in contrast to surface water) therefore, oxidation of pollutants into harmless products in groundwater does not occur.

INTEXT QUESTIONS 32.14

32.15 WATER POLLUTANTS

You have read the various sources from where pollutants enter the water bodies.

Let us now learn about the various types of pollutants arising out of these sources.

These can be broadly put under the following types.

(i) Sewage Pollutants (Domestic and Municipal Waste)

(ii) Industrial Pollutants

(iii) Agricultural Pollutants

(iv) Radioactive and Thermal Pollutants

(i) Domestic and Municipal Pollutants: The sewage contains garbage, soaps, detergents, waste food and human excreta and is the single largest sources of water pollution. Pathogenic (disease causing) microogranisms (baccteria, fungi, protozoa, algae) enter the water system through sewage making it infected. Typhoid, chloera, gastroenteritis and dysentery are commonly caused by drinking infected water.

Water polluted by sewage may carry certain other bacteria and viruses cannot grow by themselves, but reproduce in the cells of host organisms. They cause a number of diseases, such as, polio, viral hepatitis and may be cancer which are resistant to like the organic matter are oxygen demanding substances. They are responsible for deoxygenation of water-bodies which is harmful for aquatic life.

Other ingedients which enter the various water bodies are the plant nutrients, i.e., nitrates and phosphates. They support growth of algae, commonly called algal bloom (blue-green species). This process is called eutrophication and is discussed in details in the next section.

(ii) Industrial Pollutants: Many industries are located near rivers or freshwater streams. These are responsible for discharging their untreated effluents into rivers like highly toxic heavy metals such as chromium, arsenic, lead, mercury, etc. along with hazardous organic and inorganic wastes (e.g., acids, alkalies, cyanides, chlorides, etc.). River Ganges recives wastes from textile,sugar, paper and pulp mills, tanneries, rubber and pesticide industries. Most of these pollutants are resistant to breakdown by microorganisms (called nonbiodegradable), therefore damage the growth of crops and the polluted water is unsafe for drinking purposes.

Factories manufacturing plastic, caustic soda and some fungicides and pesticides release mercury (a heavy metal) along with other effluents in nearby water body. Mercury enters the food chain through bacteria, algae, fish and finally into the human body. The toxicity of mercury became evident by the Minamata Bay tragedy in Japan during the period 1953-60. Fish died due to mercury consumption and those who ate fish were affected by mercury

poisoning and quite a few died. The milder symptoms of mercury poisoning are depression and irritability but acute toxic effects can cause paralysis, blindness, insanity, birth defects and even death. The high concentration of mercury in water and in fish tissues results from formation of soluble monomethylmercury ion, (CH3, Hg+) and volatile dimethylmercury [(CH3)2 Hg] by anaerobic bacteria in sediments.

(iii) Agricultural Waste: Manure, fertilizers, pesticides, wastes form farms, slaughterhouse, poultry farms, salts and silt are drained as run-off from agricultural lands. The water body receiving large quantities of fertilizers (phosphates and nitrates or manures becomes rich in nutrients which leads to eutrophication and consequent depletion of dissolved oxygen.

Consumption of water rich in nitrates is bad for human health especially for small children.

Pesticides (DDT, dieldrin, aldrin, malathion, carbaryl etc.) are used to kill insect and rodent pests. Toxic pesticide residues enter the human body through drinking water or through food chain (biomagnification). These compounds have low solubility in water but are highly soluble in fats. For example, the concentration of DDT in river water may be very low but some fish over a period of time accumulate so much of DDT that they become unfit for human consumption. The use of pesticides in our country is increasing very rapidly.

Some of these chemicals which are highly toxic become metabolised by animals that graze on fields. Therefore, these poisonous chemicals have been often observed in the humanfood chain. The presence of these chemicals in humans even in minute amounts can cause hormonal imbalance and may lead to cancer.

(iv) Physical Pollutants: Physical pollutants can be of different types. Some of them are discussed below :

(a) Radioactive Wastes : Radionucleides found in water are radium and potassium-40. These isotopes originate from natural sources due to leaching from minerals. Water bodies are also polluted by accidental leakage of waste material from uranium and thorium mines, nuclear power plants and industries, research laboratories and hospitals which use radioisotopes.

Radioactive materials enter human body through water and food, and may be accumulated in blood and certain vital organs. They cause tumours and cancer.

(b) Thermal Sources: Various industries, nuclear power plants and thermal plants require water for cooling and the resultant hot water is often discharged into rivers or lakes. This results in thermal pollution and leads to the imbalance in the ecology of the water body. Higher temperature lowers the dissolved oxygen level (which is very essential for marine life) by decreasing the solubility of oxygen in water. Fish and other aquatic organism can get affected by a sudden change in water temperatures.

(c) Sediments : Soil particles carried to streams, lakes or oceans form the sediments. The sediment become polluting due to their large amount. Soil erosion defined as the soil carried by flood water from crop land, is responsible for sedimentation. The sediments may damage the water body by introducing a large amount of nutrient matter.

(v) Petroleum Products: Petroleum products are widely used for fuel, lubrication, plastics manufacturing, etc. and happen to be poisonous in nature.

Crude oil and other related products generally get into water by accidental spillage from ships, tankers, pipelines etc. Besides these accidental spills, oil refineries, oil exploration sites and automobile service centres pollute different water bodies. Oil slick which floats on the water surface causes death of marine life and severely affects the ecosystem of the ocean.

A list of various types of water pollutants, their sources and effects have been summarised in Table 32.1.

INTEXT QUESTIONS 32.15

1. Define water pollution.

2. List any three anthropogenic sources of water pollution.

3. List the parameters indicating water pollution.

32.16 WATER POLLUTION AND SOME BIOLOGICAL EFFECTS

The natural source of water in the form of precipitation or rain is the purest form available in nature. However, after reaching the surface and then underground it gets contaminated by a number of pollutants. There are some biological factors also mentioned earlier responsible for spoiling the quality of water. These include the lower plants like algae and bacteria which are the causes of nutrient accumulation in aquatic systems. This nutrient accumulation gives rise to a condition called eutrophication explained below.

32.16.1 Eutrophication

Eutrophication is a process by which a water body slowly becomes rich in plant nutrients such as nitrates and phosphates due to soil erosion and run off from the surrounding land. Let us try to understand this phenomenon. A water system like a lake or any reservoir may get a large inflow of organic matter from domestic wastes and run off from the surrounding land. Increasing human population, intensive agriculture and rapid industrial growth have led to an increasing release of domestic waste, agricultural residues, industrial wastes and land run-off into various water bodies. Nutrients are released from organic waste by aerobic (oxygen

requiring) bacteria which start decomposing it. Dissolved oxygen is consumed in this process. As more and more organic matter enters a water body, more is the deoxygenation of the water body and larger is the production of nutrients. These nutrients fertilize an abnormal growth of algae and other large water plants such as duckweed. As more plants grow, some of them die also due to larger oxygen demand and therefore oxygen deficiency in the water body (i.e., deoxygenation of the water body). Such a water body is said to be eutrophied and the process

is called eutrophication. The word eutrophication is derived from the Greek word which means well nourished as (eu:true, trophos:feeding)

Eutrophication of a water body results due to the release of large amount of nutrients by the action of aerobic bacteria on organic wastes entering a water body naturally or by human activity.

The above discussion leads us to a concept called biological oxygen demand (BOD). Let us try to understand by the description given below.

32.16.2 Biological Oxygen Demand (BOD)

The quality of oxygen used up by microorganisms at 27ºC and in darkness during 3 days in breaking down organic wastes in a water body is called its biological oxygen demand (BOD).

It can be explained in the following manner.

You know that there are many organic compounds or waste present in a water body. The microorganisms present in the system act upon this waste for their own consumption and growth. In the process the metabolic activity requires oxygen which is met by the dissolved oxygen present in water. It is this amount of oxygen which is defined as biological oxygen demand (BOD). The BOD value of an aquatic system depends upon:

􀁺 the type and amount of organic waste

􀁺 the organisms acting on it

􀁺 temperature and pH

The greater the amount of organic waste in the water body, the greater is the amount of oxygen required to break it down biologically and therefore higher is the BOD value of water. This value is a good measure in evaluating the degree of pollution in a water body. The less polluted water shows comparatively low value of BOD. Its value is used as a criterion for managing water pollution of a water body. An evaluation is made by determining oxygen concentration in water before

and after incubation at 20ºC in dark for 5 days.

32.16.3 Biomagnification

A variety of toxic chemicals move through food chains. Toxic pesticides may be

sprayed for controlling insect pests, fungi, herbs, but they concentrate in the food

chain and harm to other (non target) organisms. For example, DDT was sprayed

in the U.S. to control mosquitoes at a concentration expected to be harmless to

non target organisms like fish and birds. DDT accumulated in the marshes and

planktons. Planktons were eaten by fish and the fish had a higher concentration

of DDT in its body. Further, when birds ate the fish, they accumulated still higher

concentration. This increase in concentration of accumulated toxic chemicals as

one goes higher in the food chain is termed biomagnification. Biomagnification

has at times threatened the reproduction and survival of carnivores (secondary

consumers) who occupy the highest level of the food chain.

INTEXT QUESTIONS 32.16

32.17 WATER POLLUTION – SOME CONTROL MEASURES

Wastewater generated by household activity, industries or garbage landfills is called sewage which is classified as the municipal water pollution. Sewage contains solid matters in the form of suspended colloidal and dissolved organic matter, detergent, mineral matter, nutrients and gases. Sewage is one of the major causes of water borne diseases and therefore the treatment of sewage is one of the important tasks. For a long-time treatment of municipal waste in the form of sewage involved mainly of the removal of suspended solids, oxygen demanding materials and harmful bacteria. Now the disposal of the solid residue from sewage

has been improved by applying municipal treatment processes.

The treatment of this waste water is carried out in the following three stages:

(i) Primary treatment

(ii) Secondary treatment, and

(iii) Tertiary treatment

Primary Treatment: When the waste water is to be dumped off into a river or flowing steam, the treatment is carried out by sedimentation, coagulation and filtration. This is known as primary treatment. If the water is required for drinking purposes, it has to undergo further treatment called secondary and tertiary treatments. The following steps are performed to do primary treatment of water:

(i) Sedimentation: This step is carried out in large tanks specially built for this purpose in sewage treatment plant. The polluted water is allowed to settle so that silt, clay and other matter settle to be bottom and water is slowly allowed to move out. Fine particles do not settle and are thus required to be removed in the next step.

(ii) Coagulation: Fine particles and colloidal suspension are combined into large particles by a process called coagulation. This step is carried out by the addition of special chemicals called coagulants (flocculants) such as potash alum. The large particles either settle to the bottom or are moved in the next step.

(iii) Filtration: Suspended particles, flocculants, bacteria and other organisms are filtered by passing the water through a bed of sand or finely divided coal or through some fibrous materials. The total impurities collected in these steps are called sludge. It is used as a valuable fertilizer. On composting (i.e. the action of anaerobic bacteria), it releases sludge gas. It consists mainly of methane gas which is used for cooking purposes.

Secondary or Biological Treatment: The water after primary treatment is not fit for drinking purposes and has to undergo further treatment. This is done through secondary or biological treatment. A commonly used method is to allow polluted water to spread over a large bed of stones and gravel so that the growth of different microorganisms needing nutrients and oxygen is encouraged. Over a period of time a fast moving food chain is set up. For example, bacteria consume organic matter from the polluted water; protozoa live on bacteria. Every form of life including algae and fungi help in the cleaning up process. This is called secondary treatment of water. It involves the following processes.

(i) Softening: By this treatment undesirable cations of calcium and magnesium are removed from hard waters. Either water is treated with lime and soda ash to precipitate Ca2+ ions as carbonates or it is passed through cation exchangers. This makes water soft.

(ii) Aeration: In this process, soft water is exposed to air by forcing air through it to add oxygen to water. This encourages bacterial decomposition of organic matter into harmless products such as carbon dioxide and water. The addition of oxygen reduces carbon dioxide. sulphide etc.. The water is as yet not fit for drinking purposes. The pathogenic and other microorganisms need to be killed. This is done in the next treatment.

Tertiary Treatment: The tertiary treatment is actually disinfecting water.

Chlorine is the most commonly used disinfectant used for killing bacteria.

However, chlorine also reacts with traces of organic matter present in water and forms undesirable chlorinated hydrocarbons (toxic and potentially carcinogenic).

It is therefore desirable to reduce the organic matter in water before passing chlorine gas. Other methods of disinfection such as ultraviolet radiation, ozone gas treatment or reverse osmosis are preferred over chlorine treatment. But these methods are more expensive. Fig. 32.8 gives a clear picture of the process of sewage treatment in total.

Fig. 32.8 : Treatment process of sewage

The sewage treatment process involves several key steps to convert wastewater into clean, reusable water.

Preliminary Treatment: This step involves screening to remove large debris and grit from the sewage.

Primary Treatment: In this phase, the sewage is allowed to settle in large tanks, where solids sink to the bottom, forming sludge, while lighter materials float to the top and are removed.

Secondary Treatment: This biological process uses microorganisms to break down organic matter in the sewage. Aeration tanks are often used to promote the growth of these microorganisms.

Tertiary Treatment: This advanced treatment stage further purifies the water, often using chemical processes or filtration to remove remaining contaminants.

Disinfection: Finally, the treated water is disinfected, typically using chlorine or ultraviolet light, to kill any remaining pathogens before it is released into the environment or reused.

This multi-step process ensures that sewage is treated effectively, protecting public health and the environment.

In a treatment plant, the waste is passed through a series of screens, chambers and chemical processes to reduce its bulk and toxicity. During primary treatment a large percentage of suspended solids and inorganic material is removed from sewage.

The secondary stage reduces organic material by accelerating natural biological processes.

Tertiary treatment is done when water is to be reused. Here 99% of solids are removed

and various chemical processes are used to ensure that water is free from infecting materials.

INTEXT QUESTIONS 32.17

1. Define eutrophication.

2. Why does aquatic life get killed in an eutrophied pond?

3. What is the significance of BOD?

4. What is biomagnification?

32.18 SOIL POLLUTION

The adulteration of soil (land) by the addition of unwanted substances is known as soil pollution.

Sources of pollution

1. Industrial waste: The industrial wastes are the major cause of soil pollution because the wastes are toxic due to presence of cyanides, chromates, acids, alkalies, metal like nickel, cadmium, mercury and lead. Some industries like paper industries Sugar mills, textile mills and distilleries, chemical industries & cement industries are also responsible for soil pollution. The wastes of these industries are not bio-degradable.

2. Urban and domestic waste: The urban and domestic wastes referred as soil refuse, containing garbage, and rubbish, paper pieces, glass, plastics polythene bags, cans detergents and cakes. These substances emit gases, toxic hydrocarbons and pathogenic microbes cause to disease.

3. Agricultural chemicals: The fertilizers, pesticides, herbicides insecticides and fungicides are commonly used to save and increase the yield of crops but they have polluted the soil. Some time the entry of these chemicals in food chain has cause to adverse effects on health of consumers.

4. Fertilizers: The fertilizers increase the yield crop it has no doubt but the excessive use has adverse effects. It disturb the pH of soil, ionic balance and the presence of certain elements. So they have a number of health hazards. The nitrites cause to cancer in human body.

5. Pesticides: The chemicals are used to kill or to stop the growth of unwanted organisms and entry of these chemicals into food and water cause cause effect on the health of animals and human beings.

6. Insecticides: Some chemicals like DDT, BHC, aldrin, dieldrin are used to kill the insects, the use of DDT is banned by the Government because It is not biode gradable. It also effects the next crop in the field due to observed by the soil. Some biodegradable organ phosphates, carbonates may be used in place of insecticides.

7. Herbicides: The compounds used to control the growth of weeds, some inorganic compounds like sodium chlorate and sodium arsenite (Na3AsO3) were commonly used as herbicids. These one toxic in nature. So Now-adays organic herbicide Triazines are preferred.

8. Fungicides: Fungicides are used to chock the growth of fungi. Fungi is one those plants in which chlorophyll is not present i.e. they can not make their food by the process photosynthesis. They live an dead organic matters as saprophytes. Organic compounds of mercury have been used as fungicides. Many people in Iraq resulted to death due to eating breads made from grains that been treated with methyl mercury fungicide. It’s use have

many disastrous consequences because these compounds breakdown in soil.

Control of soil Pollutions: The following steps have been suggested to control the soil pollution Is:

(i) The use of chemical fertilizers can be reduced by applying bio-fertilizers and manures.

(ii) Re cycling and recovery of materials appears to be a reasonable solution for reducing soil pollutions. Materials like papers, gas and some kinds of plastics can be recycled.

(iii) Control of land loss can be attempted through restoring forests and grass cover to check soil erosion and flood.

(iv) Proper methods should be adopted for the disposal of solid wastes.

INTEXT QUESTIONS 32.18

1. What is refuse?

The urbon and domestic wastes referred as soil refuse containing.

2. Write the name of one insectide?

DDT or BHC

3. What is soil erosion?

The loss of fertile layer (dipper layer) of soil is called soil erosion.

32.19 GREEN CHEMISTRY AS AN ALTERNATIVE TOOL FOR REDUCING POLLUTION

We have discussed about hazards of environmental pollution in these units. The main reasons of this pollution is due to rapid industrialization, productions and use of toxic chemicals. An important initiative to protect the environment from chemical effluents and wastes is known as Green chemistry.

“Green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances.”

Green chemistry is environment friendly, linking the design of chemical products and processes with their impacts on human health and the environment.

Principles of Green Chemistry

(i) The use of starting materials, reagents and solvents which are less

hazardous to man and his environment.

(ii) More efficient use of raw materials.

(iii) Utilisation of chemical reactions which completely incorporate the starting materials in to final products and last amount of by product.

(iv) Search new alternatives which are environmental friendly.

(v) It is better to prevent the waste than to treat or cleanup the waste after it has been created.

Achievements of Green chemistry

(i) Development of dense phase CO2. Dense phase CO2 has been recently developed chemical product with amazing characteristics. It has ability to clean everything. It can be used as recyclable solvent and finds number of applications in food industries.

(ii) Development of fuel cells of cellular phones which can last for the full life time of the phone.

(iii) Development of process involving use of CO2 as a blowing agent for manufacture of poly styrene foam. This technology discard the use of chloro fluoro carbon.

(iv) H2O2 hydrogen peroxide gives better results and not harmful for bleaching of clothes in the laundary instead of tetrachloro ethene (Cl2C=CCl2). This compound is suspected to be carcinogenic and contiminated the ground water.

(v) Hydrogen peroxide (H2O2) is used with catalyst for bleaching papers, instead of toxic chlorine gas.

(vi) Ethanal (CH3CHO) is now a days being prepared an a commercial scale by one step oxidation of ethane in presence of ionic catalyst in aqueous solution

2 2 2 3 CH CH O Pd(II)Cu(II) CH CHO (90%)

in water

= + uuuuuuuuuuuuur

INTEXT QUESTIONS 32.19

32.20 STRATEGIES TO CONTROL ENVIRONMENTAL POLLUTIONS

Environmental pollutions affects the plants, animals and human beings as well as materials. The production and improper disposal of waste are causes for the great deal of environmental pollution. In addition to the have hold waste these wage and municipal garbage, many toxic industrial wastes from manufacturing processes require treatment and safe disposal. The biodegradable and non-biodegradable waste like polythene bags plastics, metal scrap should

be put in separate boxes. The biodegradable waste is deposited in the land fills.

Industrial wastes are also sorted as biodegradable and non-biodegradable, should be put in separate boxes. Fly ash, furnace stag mud and failings and gypsun like non-biodegradable wastes have produce great problem. Some chemical industries producing inflammable wastes and hazardous chemicals as by products.

Some methods are usually employed one given below

1. Recycling: When materials one recycled, there are several benefits, apart from savings on the cost of raw materials, waste disposal costs are reduced.

(i) the collections and recycling of glass.

(ii) Iron scrap can be used in manufacturing steel.

(iii) Polythene bags and plastics can also recycled.

(iv) The newspapers, used copies, and magazines can be used for making papers.

Sewage treatment

Sewage is the liquid waste which includes house hold wastes, Industrial wastes ground wastes, etc. which contains 99.9 water with inorganic, organic matters in dissolved, suspension and colloidal states. It involves the following stages.

(i) The removal of large solid particles. It can be done by screening and sedimentation. The solid wastes are deposited in land fillsites.

(ii) It is allowed to stand is tanks. Many solids settle down by the use of the chemicals like alums and ferrousulphate while oil, grease, float on the surace which can be shimmed off.

(iii) Next stage involve the biological oxidation of organic content of waste materials by microorganisms followed by filtration.

(iv) Finally some physical and chemical processes are applied to remove some chemicals like phosphates and adding chlorine to improve the quality of waste water.

(i) Incineration: It convert the organic and biogical wastes to carbon dioxide and water at higher temp 1273 k and excessive supply of oxygen. Exhaust gases must be filtered. The incomplete oxidation of Poly chlorinated biphynyls (PCBs) may convert to toxic polychlorobidenzodioxins (PCDDs).

Main problem of this process is air pollution due to incomplete oxidations.

(ii) Digestion: In digestion, sluge is kept in a closed tank in the absence of air for a prolonged period whereby it goes anaerobic respirations, yields gases like carbon dioxide methane and ammonium sulphide. The methane gas can be used as fuel.

2(CH2O) —→ CO2 + CH4

(iii) Dumping: Dumping of the sewage stage into sea has been very common.

However dumping of the sluge into land is increasing now-a-days. Because it has nitrogen and phosphorous which act as fertilizers for the soil.

INTEXT QUESTIONS 32.20

1. Write the names of those wastes which can be recycled

Glass, polythene, ion, paper etc.

2. Name the chemicals which are used in sedimentation of solid waste.

Potash Alumns and ferrous sulphate.

3. How the incrination cause to air pollutions?

The conversion of biological wastes to CO2 and water at 1273 K. The incomplete oxidation PCBS are also causes to air pollutions.

WHAT YOU HAVE LEARNT

􀁺 Surroundings in which we live is our environment.

􀁺 There are two components of environment : physical or abiotic and living organisms or biotic

􀁺 Pollutants may be defined as substances added to natural surroundings.

􀁺 There are two major sources of pollutants - stationary and mobile.

􀁺 Pollutants have adverse effects on environment and living organisms.

􀁺 SO2, CO2, CO, smoke, Pb, Hg, CFC, etc. pollute air. Their sources and effects are varied.

􀁺 Pollution in simple words is the unhealthy and harmful condition for living organisms and non-living things.

􀁺 Pesticides, plastic, detergents, chlorine, mercury, etc. pollute water and endanger life of aquatic organisms.

􀁺 Unwanted sounds are termed as noise. Sounds is measured in decibels. Beyond 70 decibels noise has harmful effects on humans.

􀁺 The Government of India has set up various environmental laws and judiciary system to punish the polluters.

􀁺 Nature’s balance has beeen upset by human activities releated to urbanisation, industrialisation and intensive agriculture.

􀁺 Atmosphere is made up of gases of which nitrogen - 78%, oxygen - 21%, carbondioxide - 0.1 to 0.3%, inert gases 1 %

􀁺 Increase of temperature with altitude is known as positive lapse rate whereas decrease in temperature with increase of altitude is negative lapse rate of temperature.

􀁺 Air pollution is due to

(i) particulate matter (soot, dust)

(ii) aerosols composed of hydrocarbons

(iii) gases like SO2, NO2 are mostly released by burning fossil fuels.

􀁺 NO2 and hydrocarbons are modified by sunlight to form photochemical smog.

Smog is a combination of smoke and fog. Automobile exhausts give out NO2 and hydrocarbons. They form PAN (peroxyacetyl nitrate) which along with ozone and SO2 forms photochemical smog.

􀁺 Smog cools and settles down near the earth and forms a blanket, while warmer air covers it. Thus there is a ‘temperature inversion’ with warm air above and cool air below unlike in the normal conditions.

􀁺 SO2 and NO2 form acids which drop as H2SO4 and HNO3 on statues and spoil them. This is called acid precipitation. Acid rain kills trees, prevents reproduction in fish and causes poor visibility.

􀁺 Greenhouse gases are CO2, NO2, CH4, chlorofluorocarbons and halons. They trap solar radiation and cause global warming.

􀁺 Global warming due to greenhouse effect leads to drought, rise in sea level, lack of rain and water shortage.

􀁺 There is a layer of ozone in stratosphere, which protects us from UV radiation by absorbing it.

􀁺 Chlorofluorocarbons which are used in refrigerators and foam cups as aerosols and halons used in fire extinguishers, when released into the air cause depletion of ozone shield which protects us from harmful effects of solar radiations. It is feared that ozone depletion will have damaging effects on humans such as causing skin cancer.

􀁺 Complete destruction of ozone layer over an area is termed as ozone hole.

􀁺 Air pollution causes respiratory diseases such as emphysema and bronchitis, eye irritation, fluoroisis, cancer and may even be fatal.

􀁺 Control measures include use of sulphur free oil and coal, use of alternative sources of energy such as wind and solar power, use bicycle and battery powered vehicles, stop burining waste indiscriminately, have stringent measures for release of emissions from industries and above all educate general public and caution them against releasing air pollutants.

􀁺 Water pollution refers to any physical, chemical or biological change that has an undesirable affect on living organisms.

􀁺 Sewage, industrial, agricultural pollution and physical pollutants are the various sources of water pollution. These sources may be limited to a point sources or spread over large areas (non-point sources).

􀁺 Sewage, fertilizers, detergents, toxic wasters released by industries are some of the sources of groundwater pollution.

􀁺 Phosphatic, and nitrogenous fertilizers cause algal bloom and severe oxygen depletion in water body. The water body is said to be eutrophied.

􀁺 The quantity of oxygen needed by micro-organisms in degrading organic wastes in a water body is defined in terms of its biological oxygen demand (BOD).

􀁺 Biological magnification of toxic materials released into water bodies poses a serious threat to aquatic life and eventually to human life.

􀁺 Polluted water may be made useful for human consumption by subjecting it to various treatments.

􀁺 Legislative measures have been enacted in our country to restrict the pollution of various water bodies.

TERMINAL EXERCISE

1. What is environment?

2. Explain the term anthropogenic pollutants.

3. Write four major pollutants of water, their sources and effects.

4. Differentiate between the Primary and Secondary Pollutants.

5. What are the damaging effects of SO2 and NO2 on plants and animals?

6. Write a note on carbon monoxide poisoning.

7. What is thermal inversion and how is it caused?

8. Enumerate the various effects of acid rain.

9. What is ozone hole? What are the effects of ozone depletion?

10. Why does sea level rise due to global warming?

11. How do greenhouse gases cause global warming.

12. Mention five disease/discomforts in humans caused by different air pollutants.

13. Enumerate the various measures of control of air pollution.

14. How the industrial wastes and domestic wastes are helpful in soil pollution?

15. What one fungicides.

16. How to control soil pollution?

17. Explain main effects of water pollutions.

18. What are the various types of water pollutants? State their consequences.

19. What are the effects of detergents on fresh water bodies?

20. What are the various sources of groundwater pollution?

21. How is the disease ‘methaemoglobinaemia’ caused?

22. How can domestic waste be used as manure?

23. What will be the problem arise due to abundance of phyto plankton?

24. Write in brief about sewage treatment.

----------------------------

A clean environment is very necessary to live a peaceful and healthy life. But our environment is getting dirty day by day because of our negligence.

Earth is currently facing a lot of environmental concerns like air pollution, water pollution, and noise pollution, global warming, acid rain, biomagnification, eutrophication, deforestation, waste disposal,ozone layer depletion and climate change.

Over the last few decades, the exploitation of our planet and degradation of our environment

have gone up at an alarming rate. As our actions have not been in favour of protecting this planet, we have seen natural disasters striking us more often in the form of flash floods, tsunami and cyclones.

“Every individual should be environmentally aware, regardless of whether they work with

environmental issues or not.”

12.1 Pollution

12.2 Air Pollution

12.3 Water Pollution

12.4 Noise Pollution

12.5 Agrochemicals

12.6 Biomagnification

12.7 Eutrophication

12.8 Organic Farming and its Implementation

12.9 Solid Waste Management

12.10 Ecosan Toilets

Learning Objectives

• Gain knowledge about our environment and its importance.

• Get to know about the effects and aftereffects of human activities on climate and ecosystem.

• Know about eco-friendly practices for pollution mitigation.

• Acquire insights into solutions to environmental problems.

• Understand the need for peoples’ participation in environmental protection.

• Understand the importance of clean environment.

12.1 Pollution

Pollution is any undesirable change in the physical, chemical and biological characteristics

of the environment due to natural causes and human activities. The agents which cause

pollution are called pollutants. Pollution is classified according to the types of environment

that is affected. They are mainly air, water and

soil pollution.

12.1.1 Classification of Pollutants

In terms of eco-system, pollutants can be classified into two basic groups – non-degradable and degradable. Based on the time taken to breakdown into their ingredients, degradable pollutants are classified as rapidly degradable (non-persistent) and slowly degradable (persistent).

a) Rapidly degradable or non-persistent pollutants: These can be broken down by natural processes. Domestic sewage and vegetable waste are examples of such pollutants.

b) Slowly degradable or persistent pollutants: These are pollutants that remain in the environment for many years in an unchanged condition and take decades or longer to degrade, as in the case of DDT.

c) Non-degradable pollutants: These cannot be degraded by natural processes. Once they are

released into the environment, they are difficult to be eliminated and continue to accumulate

(biomagnification). Toxic elements like lead, mercury, cadmium, chromium and nickel are

such common pollutants.

12.2 Air Pollution+

Earth is surrounded by a gaseous envelope which is called atmosphere. The gaseous

blanket of the atmosphere acts as a thermal insulator and regulates the temperature of the earth by selectively absorbing The UV rays of solar radiation. The adverse effects of pollution include depletion of Ozone by Chlorofluorocarbons or CFCs, used as refrigerants and global warming by elevated CO2 (industries, deforestation, and partial combustion).

The alterations or changes in the composition of the earth’s atmosphere by natural or human

activities (anthropogenic factors) are referred as Air Pollution.

Pollutants include the abundant presence of solid, liquid or gaseous substances produced by human or natural activity. The nature and concentration of a pollutant determine the severity of detrimental effects on organisms and human health. Along with

atmospheric factors (humidity, precipitation,

wind, air currents, altitude) prevailing at a place

and time, its effects can be far reaching and

catastrophic.

Air pollutants can be

• discharge of dusts or particulate matter

(PM : 2.5 μm)

• discharge of gases (SO2, NO2, CO, CO2)

Carbon monoxide (CO) is produced mainly

due to incomplete combustion of fossil fuels.

Automobiles are major causes of CO pollution

in large cities and towns Automobile exhausts,

fumes from factories, emission from power

plants, forest fires and burning of fire-wood

contribute to CO pollution.

With rapid urbanization, major amount of

carbon dioxide and sulphur dioxide (SO2) is

released in the atmosphere. From automobiles,

aeroplanes, power plants and other human

activities that involving the burning of fossil

fuels (coal, oil etc.,) CO2 is the main pollutant

that is leading to global warming.

Nitrogen oxides are also major air

pollutants. Fossil fuel combustion and

automobiles exhausts are the source of

nitrogen oxides. Sulphur dioxide and nitrogen

oxides are the major causes of acid rain.

Particulate matters are tiny particles of

solid matter suspended in a gas or liquid.

Combustion of fossil fuels, fly ash produced

in thermal power plants, forest fires, asbestos

mining units, cement factories are the main

sources of particulate matter pollution.

12.2.1 Sources

The main sources of air pollution (Fig12.1) are:

• Transport sources – cars, buses, airplanes,

trucks, trains

• Stationary sources – power plants,

incinerators, oil refineries, industrial

• Area sources – agricultural - wood /

stubble burning, fireplaces

• Natural sources – wind-blown dust,

wildfires, volcanoes.

12.2.2 Effects of Air Pollution

• Affects all organisms as they depend on the

atmosphere for respiration.

• Causes irritation in the throat, nose, lungs

and eyes. It causes breathing problems and

aggravates existing health conditions such

as emphysema and asthma.

• Contaminated air reduces the body’s

defense mechanism and decreases the

body’s capacity to fight other infections

in the respiratory system.

• Frequent exposure to polluted air increases

the risk of cardiovascular diseases.

Breathing air that is filled with fine

particulate matter can induce hardening of

the arteries, triggering cardiac arrhythmia

or even a heart attack.

• People who exercise outdoors can

sometimes be susceptible to adverse effects

of air pollution because it involves deeper

and faster breathing. Hence it is advisable to

walk or jog in the mornings in places with

ample tree cover.

• Gas leaks can be lethal or affect the quality

of air in the affected area.

• CO in the atmosphere interferes with O2

transport since haemoglobin has greater

affinity for carbon monoxide. At low

concentration it causes headache and

blurred vision. In higher concentration, it

can lead to coma and death.

12.2.3 Other notable effects of Air

Pollution

Smog is a type of air pollution caused by tiny

particles in the air. The word comes from a

mixture of the words smoke and fog .

Today, smog generally refers to photochemical

smog, which is created when sunlight reacts

with nitrogen oxides and volatile organic

compounds found in fossil fuel emissions

from automobiles, factories, and power plants.

These reactions create ground-level ozone and

particulate matter, reducing visibility. Smog can

make breathing more difficult, especially for

people with asthma.

Smog also affects plants and animals. It

damages crops as well as causes health problems

in pets, farm animals and human beings. Smog

has also been known to cause corrosive damage

to buildings and vehicles.

Peroxyacetyl nitrate (PAN) is a secondary

pollutant present in photochemical smog. It

is thermally unstable and decomposes into

peroxyethanol radicals and nitrogen dioxide

gas causing eye irritation.

Global warming: Increase in the

concentrations of greenhouse gases such as

CO2, methane, nitrous oxide, CFCs, and ozone

causes greenhouse effect, warming of the earth,

resulting in sea level rise, submerging of islands

and sea shores of various parts of the world.

Ozone depletion: Thinning of the

stratospheric ozone layer is known as ozone

depletion. Such depletion causes the ‘ozone hole’,

resulting in poor screening of the harmful UV

rays and increase in incidences of skin cancer.

Some of the common agents that deplete ozone

are CFCs.

Acid rain: Acid rain is a form of precipitation

that contains acidic components, such as

sulphuric acid or nitric acid. It damages trees,

crops and harms marine animals (coral reefs)

and induces corrosion.

facilities, and factories

NIOS Lesson 32 - ENVIRONMENTAL CHEMISTRY

🌍 Major Natural Air Pollutants

1. Greenhouse gases

2. Volcanic emissions

3. Wildfire pollutants

4. Dust and sand storms

5. Biological pollutants

6. Oceanic sources

7. Radioactive pollutants

📊 Summary Table

🔹 Major Anthropogenic Air Pollutants

1. Carbon monoxide

2. Sulphur oxides

3. Nitrogen oxides

4. Particulate matter

5. Volatile organic compounds

6. Heavy metals

7. Chlorofluorocarbons (CFCs)

📊 Natural vs Anthropogenic Pollutants

⚠️ Key Insight

🔹 Classification of Air Pollutants

1. Primary pollutants

2. Secondary pollutants

🔹 Other Classification Methods

By State of Matter

By Source

📊 Comparison Table

🔹 Classification of Water Pollutants

1. Organic pollutants

2. Pathogens

3. Nutrients

4. Suspended solids

5. Inorganic pollutants

6. Thermal pollution

7. Radioactive pollutants

📊 Summary Table

🔹 Classification of Soil Pollutants

1. Organic pollutants

2. Inorganic pollutants

3. Radioactive pollutants

4. Biological pollutants

5. Industrial pollutants

6. Agricultural pollutants

7. Urban pollutants

📊 Summary Table

⚠️ Local Context (Tamil Nadu)

🔹 Key Features of Tannaries

1. Raw material

2. Tanning process

3. Pollutants

4. Products

📊 Environmental Impact

Major Air Pollutants Overview

Key Insights

Major Water Pollutants Overview

Key Insights

Major Soil Pollutants Overview

Key Insights

🔹 Classification of Atmospheric Pollutants

1. By Origin

2. By Physical State

3. By Source

4. By Chemical Composition

📊 Comparison Table

⚠️ Risks & Impacts

Schematic diagram illustrates water contamination due to natural sources (droughts and floods) and anthropogenic sources (industrial, agriculture, and urban activities), their pathways, receptors, and other types of pollution

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