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Environmental Chemistry

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Environmental Chemistry. What is environmental chemistry?. Study of Chemical species Origin Transport Reactions Effects Fate. MOST IMPORTANT ASPECT OF EN.CHEMISTRY. ENVIRONMENTAL POLLUTION. What Does It Mean? - PowerPoint PPT Presentation

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Page 1: Environmental  Chemistry

Rimmy Augustine 1

Page 2: Environmental  Chemistry

Rimmy Augustine 2

What is environmental chemistry?

Study of Chemical species

Origin

Transport

Reactions

Effects

Fate

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ENVIRONMENTAL POLLUTION

What Does It Mean?

Introduction of pollutants into the environment

that causes undesirable changes and has

harmful effects on plants, animals, and human

beings

MOST IMPORTANT ASPECT OF EN.CHEMISTRY

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Pollutants − Waste materials, which cause pollution

1.Biodegradable waste/pollutant − Breaks down easily

Examples: food and garden waste, human waste, etc.

2.Non-biodegradable waste − Not easily degradable

Examples: plastic, glass, heavy metals, etc.

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ENVIRONMENTAL POLLUTION - TYPES

ATMOSPHERIC POLLUTION

SOIL POLLUTION

WATER POLLUTION

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ATMOSPHERIC POLLUTION Atmosphere ?

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ATMOSPHERIC POLLUTION- types

1. Tropospheric pollution

2. Stratospheric pollution

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1. Tropospheric pollution

a. Gaseous air pollutants Oxides of sulphur Oxides of nitrogen Oxides of carbon hydrocarbons

b. Particulate pollutants• Smoke• Dust • Mists • Fumes

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Oxides of sulphur

Example: SO2 and SO3

Formation:

burning S containing substances

Catalytic oxidation of SO2 to form SO3

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Harmful effects?

• Irritation to throat and eyes

• Asthma, bronchitis, respiratiory diseases

• Damage to plants,loss of chlorophyll, stiffness of flower buds

• Damage to buildings, (Taj Mahal)

Sink/ control

Lime stone acts as a sink. It reacts with sulphuric acid

Remove sulphur from fuels

Use hydroelectric or nuclear power plants

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Oxides of nitrogen

Example: NO(nitric oxide) and NO2(nitrogen dioxide)

Formation:

during lightning strikes

Nitric oxide reacts with ozone

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Harmful effects?

• Irritant red haze in traffic

• Asthma, bronchitis, respiratory diseases

• Damage to plants, retard photosynthesis

• Harmful for fibres and metals

Sink/ control

Gases get converted to nitric acid

Removed from atmosphere by acid rain

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Oxides of carbon

Example: CO and CO2

Formation: CO

incomplete combustion of carbon or fuel

Dissociation of CO2 at high temperature

Conversion of methane

Sink/ control

microorganisms present in soil convert CO to CO2

Catalytic convertor fitted to exhaust pipes

Use CNG or LNG instead of petrol, diesel

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Harmful effects?

• Causes CO poisoning

• Form carboxy haemoglobin

• 300 time more stable than oxy haemoglobin

• Loses capacity to carry oxygen

• Leads to cardio vascular disorder

• Causes anoxia(acute oxygen starvation)

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Formation: CO2

respiration

Burning of fuel

Decomposition of carbonate salts

Sink/ control

green plants

Control burning substances

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Green house effect

Atmosphere traps the sun’s heat near the earth’s surface

and keeps it warm. It is called green house effect

GLOBAL WARMING

Carbon dioxide also trap heat. If the amount of carbon dioxide

crosses the delicate proportion of 0.03 per cent, the natural green

house balance may get disturbed and lead to global warming.

Green house gasesCarbon dioxide, methane, water vapour, nitrous oxide, CFCs, and ozone.

ANIMATION

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Assignment

What is acid rain?

How is it caused?

What are its harmful effects?

How to control it

TWO A4 SIZE PAGES

ANIMATION ACID RAIN

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PARTICULATE POLLUTANTS

Small solid particles and liquid droplets suspended in air

are collectively called as particulate pollutants

A. Viable particulates

B. Non viable particulates

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VIABLE PARTICULATES

Viable particulates are minute living organisms that are dispersed

in atmosphere. Bacteria, Fungi, moulds etc.

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NON - VIABLE PARTICULATES1. SMOKE: Solid carbon particles formed during combustion

2. DUST: Solid particles formed during crushing and grinding

3. MIST: Particles of spray liquid and condensation of vapours in the air

4. FUMES: vapours of certain material present in air

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HARMFUL EFFECTS OF PARTICULATES

a. Particulates entering the lungs causes cancer, asthma, bronchitis etc

b. Lead particulates causes retarded memory

c. It retards photosynthesis in plants

d. Leads to poor visibility in roads

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SMOG (Smoke + Fog)A. London smog/ Classical smog/reducing smog

It killed many people in London

Occurs in cool humid conditions

Mixture of smoke, fog and sulphur dioxide

Due to presence of Carbon it is reducing in nature

1. LONDON SMOG

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SMOG (Smoke + Fog)

B. Photochemical smog /Los Angeles smog/Oxidising smog

First observed in Los Angeles

Occurs in warm dry and sunny climate

In presence of sunlight NO2 and hydrocarbons gets converted to

harmful products like PAN, aldehyde, ketone, ozone and nitric

oxide.

Ozone and NO2 are oxidising in nature

HARMFUL EFFECTS

Powerful eye irritants

Causes headache chest pain cough

Extensive damage to plant life

ANIMATION

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Los Angels photochemical smog

ANIMATION

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CHEMISTRY OF PHOTOCHEMICAL SMOG

1. Sunlight breaks down NO2 to NO and oxygen free radical

2. Ozone is produced by the reaction between O and O2

3. Ozone forms more NO2 by reaction with NO

Ozone initiates other free radical mechanisms to form

PAN(Peroxy acetyl nitrate,aldehyde and ketone

O(g) + O2(g) O3(g)

CH4(g) + O3(g) HCHO + CH2 = CH-CHO + CH3COOONO2

METHANAL ACROLEIN PAN

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CONTROL OF PHOTOCHEMICAL SMOGCatalytic converters in automobiles reduces NO2 and hydrocarbonCertain plants like Pinus, Juniparus and Vitis metabolise nitrogen oxides

PINUS

JUNIPERS

Vitis (grape wines)

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GROUP A (601 -615)/ (644 -660)/(194-207)WATER POLLUTION

Major water pollutants Causes (1) pathogens (2) organic wastes stress on BOD International standards for drinking water

GROUP B ( 616 – 630) /(661 – 675)/(208-220)SOIL POLLUTION

Major Pollutants Causes Pesticides Industrial waste

GROUP C ( 631 – 643) /(676 -687)/(221- 233)Strategies to control environmental pollution

Waste management Green chemistry

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Stratospheric Pollution

Ozone hole

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Ozone Layer

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Ozone Layer importance

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If no Ozone layer???????More UV rays reaches earth

Ageing of skincataract

Sun burnSkin cancer

Evaporation of surface water

Damage to phytoplankton and fishes

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Ozone layer formation

UV rays split oxygen molecules into free oxygen atomsOxygen atoms combine with molecular oxygen to form ozone

Ozone further absorbs UV rays and split into dioxygen and an oxygen atom.A dynamic equilibrium exists between production and decomposition of ozone

O(g) + O2(g) O3(g)

uvO3(g) O2(g) + O(g)

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Ozone layer depletion

CFCs from different sources reach the stratospherePowerful UV rays break them down to free radicals

Chlorine radical react with ozone to form O2 and chlorine monoxide

Chlorine monoxide produces more chlorine radicals by reacting with oxygen atoms

Process gets repeated leading to more break down of ozone

ANIMATION

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OZONE DEPLETION BY CHLORO FLUORO CARBONS

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OZONE HOLE OVER SOUTH POLE

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OZONE HOLE OVER SOUTH POLE

Summer climate: - sink for chlorine free radical / less ozone depletion

Nitrogen dioxide combines with chlorine monoxide to form chlorine nitrate which is non reactive.

Methane combines with chlorine free radical to form methyl free radical and HCl. Chain reaction stops.

Winter climate:- Polar stratospheric clouds(PSC)/ an initiator for depletion A. In presence of PSC chlorine nitrate gets hydrolysed to hypochlorous acid.

B. In presence of PSC chlorine nitrate gets hydrolysed to Cl2 .

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spring season:- Ozone depletion by chain reactionIn sunlight HOCl and Cl2 are photolysed to free radicals causing ozone depletion