Environmental Chemistry
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Transcript of Environmental Chemistry
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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