PollutionPollution

Effect of undesirable changes in our surroundings that

have harmful effects on plants, animals & human beings.

From an ecological perspective, pollutants classified as:(i) Degradable or non-persistent pollutants : e.g.,

domestic sewage, discarded vegetables, etc.(ii)Slowly-degradable or persistent pollutants: e.g., DDT

(pesticides) & most plastics.(iii)Non-degradable pollutants: e.g., toxics like lead or

mercury, & nuclear wastes.

Pollution

• Air pollution

• Water pollution

• Soil pollution

• Marine pollution

• Noise pollution

• Thermal pollution

Air pollutionAir pollution

Air pollution: presence of undesirable solid or gaseous particles in the air in quantities that are harmful to human health & environment

Air PollutionAir Pollution

Air pollutionAir pollution

• Primary pollutants : Carbon monoxide, carbon dioxide, nitrogen oxides, sulfur oxides, volatile organic compounds, & suspended particulate matter

• Secondary pollutants: sulfuric acid, nitric acid, carbonic acid, etc.

Air Pollution

Air pollution control act in India was passed in 1981 & Motor Vehicle Act was passed in1988

Total Sources

Stationary Sources Mobile Sources

Point Area Sources Line Sources Area Sources

1. Industrial Processing 1. Residential & industrial areas 1. Highway vehicles 1. Motor vehicles -2. Power plants 2. On site incineration 2. Railroad locomotives Light-duty/Medium duty/heavy duty3. Fuel combustion 3. Open burning sites 3. Channel vessels 2. Railyard locomotives (Industrial) Coal, Oil, Gas4. Soil waste disposal 3. Port vessels Municipal incinerators 4. Aircraft (airports)5. Miscellaneous 5. Miscellaneous

TYPES OF PARTICULATESTYPES OF PARTICULATES

• Aerosol• Mist • Smoke • Dust• Fume • Plume • Fog• Smog

TYPES OF PARTICULATES:

Term Meaning Examples

Aerosol general term for particles suspended in air Sprays from pressurized cans

Mist aerosol consisting of liquid droplets Sulfuric acid mist

Dust aerosol consisting of solid particles that are blown Dust storm

into the air or are produced from larger particles by

grinding them down

Smoke aerosol consisting of solid particles or a mixture of Cigarette smoke, smoke from

solid and liquid particles produced by chemical reaction burning garbage

such as fires.Plume column of one fluid moving to another.

Fume generally means the same as smoke but often applies Zinc/lead fumes

specifically to aerosols produced by condensation of hot

vapours of metals

Fog aerosol consisting of water droplets

Smog term used to describe a mixture of smoke and fog

(1)Air pollution on animals : Direct: inhalation Indirect :accumulation of air borne contaminants on the vegetation: poisoning, reduction in yield

Effect on healthSymptoms could include lack of appetite, rapid loss in weight, lameness, diarrhea & subsequently death.

(2)Effects on plantsnecrosis, chlorosis, abcission, epinasty

(3)Effects on materials(4)Effect on the stratosphere: ozone

Effect of air pollution

• Toxic air pollution: cancer, genetic mutation, birth defects etc – Bhopal gas tragedy

• Smog: a combination of fog and smoke –in the cities: 4000 people died in London in 1952:

all types of respiratory ailments• Photochemical smog• : particulates, nitrogen oxides, ozone,

aldehydes, peroxyacetyl nitrate (PAN), unreacted HC

Case study: SingaporeCase study: Singapore

• Cost for car ownership

• Public transport

• Area licensing scheme

• 45.3% reduction

Structure of the atmosphere:

Troposphere, stratosphere, mesosphere and thermosphere.

Dispersion of air pollutantDispersion of air pollutant

• Lapse rate: change in rate of temperature in the layers of troposphere ELR

• Prevailing lapse rate – env. Lapse rate: using a balloon with thermometer

• Adiabatic lapse rate: = When a packet of hot air is taken to the upper atmosphere its temperature and density becomes equal to the surrounding atmospheric air . The rate at which this air cools without addition or removal of energy is called ALR mathematically calculated

• ALR is between

9.8 deg/km –6deg/km for

dry and saturated gas resp. ALR

• 1.ELR > ALR – i.e RATE OF COOLING AT A PLACE WITH RESPECT TO ALTITUDE IS MORE THAN THEORITICAL ALR

• Super adiabiatic lapse rate– Helpful to dessipate pollutants into the upper

atmosphere– Lessen the air pollution problems

• 2. ELR<ALR – Atmosphere is stable and prevailing ELR is called Sub adiabiatic lapse rate– Dispersion of pollutants slower

• 3.ELR = ALR - isothermal– Atmosphere neutral

• 4.Negative lapse rate / Inversion– Atmospheric temperature increases with altitude causes

negative LAPSE RATE .– Warm air lies over the colder air below .– It is a very stable environment – Dispersion of pollutants very poor– Hot gases goes not ascend above inversion layer– Major cases of pollution tragedies in the world leading to

death

ELR > ALR – Super adiabiatic lapse rate

ELR<ALR – Sub adiabiatic lapse rate

Negative lapse rate / Inversion

Figures from Benny Joseph

Dispersion of pollutantsDispersion of pollutants

• Impact of wind

• Lapse rate and dispersion

Different types of plume behavioursDifferent types of plume behaviours

Figures from Benny Joseph

• Looping: highly unstable atm – higher chimneys req. but automobile

• Neutral: ELR ≈ ALR• Coning: slightly stable atm, clouds cover the region,

sub adiabatic, wind speed 32km/hr• Fanning: no vertical mix, extreme inversion

condition by –ve ELR• Lofting: strong super ALR above a surface

inversion, min down ward mixing: most ideal case • Fumigating: Inversion layer occurs at short distance

above the top of stack: dangerous• Trapping: two inversions above and below, trapped,

dangerous

Control vs preventionControl vs prevention

Prevention-

• Changing raw material: low sulfur coal to fuel oil (sulfur dioxide emission)

• Process conditions

• Procedures

• Preventive maintenance: check leakages

Air pollution control Techno.Air pollution control Techno.

Depends upon the pollutant and situation

• Settling chambers

• Cyclone separator

• Electronic precipitator

• Fabric filter

• Wet collector

Technologies usedTechnologies used

• Condensation

• Absorption

• Adsorption

• Combustion

Catalytic converter of automobilesCatalytic converter of automobiles

• Efficiency E = Win-Wout X100% W in• Depends upon-

– The pressure drop– The space requirement– The initial operating cost– Whether the SPM is collected in dry or liquid

form– Temperature of emission gas

• Cyclone separator

• Bag filter

• Electrostatic separator

• Absorption and wet scrubbing equipment

Cyclone separatorCyclone separatorSelf reading

• Legal aspects of air pollution control in India:

• The air (prevention & control of pollution) act was legislated in 1981.

• Environmental protection act (EPA) was passed in 1986.

• The Central Motor Vehicles act of 1939 was amended in 1989.

• The exhaust emission rules for vehicle owners notified in 1990 and the mass emission standards

• for vehicle manufacturers were enforced in 1991, revised in 2000.

• Integrated approach with strict air pollution control laws : some suggestions:

• Putting a greater emphasis on pollution prevention rather than control.

• Reducing the use of fossil fuels.

• Improving the quality of vehicular fuel.

• Increasing the use of renewable energy.