2 air pollution
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air pollution iit roorkeeTRANSCRIPT
Air Pollution
Air & Its Pollution
A person needs per day about– 1.4 kg of water– 0.7 kg of food– 14 kg of air
Air Pollution
Air pollution may be defined as the presence in the air (outdoor atmosphere) of one or more contaminants or combinations there of in such quantities and of such durations as may be or tend to be injurious to human, animal or plant life, or property, or which unreasonably interferes with the comfortable enjoyment of life or property or conduct of business.
Air PollutantsA pollutant can be solid (large or sub-molecular),
liquid or gas .It may originate from a natural or anthropogenic
source or both.It is estimated that anthropogenic sources have
changed the composition of global air by less than 0.01%.
However, it is widely accepted that even a small change can have a significant adverse effect on the climate, ecosystem and species on the planet.
Examples of these are acid rains, CO, SOx, NOx, SPM, RSPM,CO2, ozone in the lower atmosphere, and photochemical smog.
Air Pollution and Public Opinion• Not a new phenomena: Smoke from Burning of
Coal• Problems in many urban areas in late 1800s and
early 1900 due to coal use• 1000s of deaths attributed to air pollution
episodes in London – large number of pollution sources– restricted air volume– failure to recognize problem– CO presence: lethal
• Photochemical smog
Why Air Quality?Sources of Air Pollution
1.Point source stacks of thermal power stations, brick kilns, lime kilns, boiler etc.
2. Area source Cluster of point sources, spill of chemicals, crude/product spills in ocean etc.
3. Line source Car, scooter, train, aircraft: white line in sky behind a jet plane?
Why Air Quality?Type of Pollutants
1. Primary pollutants pollutants which are being emitted into the air directly by point/area/line
sources. Examples: CO, NOx, SOx, Pb, SPM, RSPM, VOCs
2. Secondary pollutants pollutants which are getting formed from primary pollutants in the atmosphere. Some of the reactions are catalyzed by sun light.
Examples: acid rains, smog, O3, H2O2, formaldehyde, peroxy acetyl nitrate (PAN)
Why Air Pollution?
• Main cause: Combustion
Fuel (C,H,S,N,Pb,Hg,ash) + Air (N2 + O2)
CO2, CO, NOx, SOx, Pb, Hg, SPM, RSPM(PM10), VOCs
Coal: 450 MT
Crude based products:120 MT
Natural gas: 60 NBCM
Biomass: 350-400 MT (NOX,SPM/RSPM)
Why Air Pollution contd..
Usage/handling of Chemicals: paint, varnishes, perfumes, CFCs, petrol pumps, etc.
Cement handling, insulation on winding of motors/alternators/transformers
Combustion processes
1.Electricity generation Total generation capacity: 162,366.80 MW
Thermal : 104,423.98 MW (64.6%)
Hydro : 36,953.40 MW (24.7 %)
Nuclear : 4560.0 MW (2.9%)
Renewable : 16,429 MW ( 7.7%)
2.Transport : 18 % of total energyLiquid fuels : 97.5% total petroleum products
Electricity : 1.0% of total
3. Industry :coal, petroleum products, electricity
4. Domestic sector :biomass, petroleum products, electricity
5. Agriculture :electricity, petroleum products
If the Indian coal is burnt at a rate of 1.00 kg per second having a sulphur content of 1.00 %, what is the annual rate of emission of SO2. The sulphur in the ash is found to be 5 %.
• Sulphur burnt: 1.00 x 1/100=0.01 kg/s• Sulfur converted to SO2 = 0.01 x 0.95 = 0.0095 kg/s• S + O2 =SO2• SO2 produced = 0.0095 x 64/32 = 0.019 kg/s or 600,000 kg/y
Coal combustion having S
Pollutants generation
Fuel Combustion
VOC1%
Pb5%
CO3%
Sox43%
Nox25%
PM1023%
Sox
CO
Pb
Nox
VOC
PM10
S in coals:0.5-2.5%
N2+O2=NOx
Transport
VOC17%
PM1010%
Nox21%
Sox1%
CO36%
Pb15%
Sox
CO
Pb
Nox
VOC
PM10
India, Diesel:350 ppm2010: 50 ppmUS/EU: 15 ppm
Octane number enhancer: Tetraethyl lead, GM 1922
India: 2000
Industrial
VOC51%
PM1028%
Nox3%
Sox8%
CO6%Pb
4%
Sox
CO
Pb
Nox
VOC
PM10
SOx
51%
The Air (Prevention and Control of Pollution) Act, 1981 Central pollution control board (CPCB) State pollution control boards (SPCB)/committees
Set procedure : ambient air, industry wise norms FIR against the firm/sealing of the industry
Agencies responsible for monitorring air pollution in India
National Ambient Air
Quality Standards (NAAQS)in India,
1994
Concentration in ambient air Pollutants Time-weighted average
Industrial Areas
Residential, Rural &
other Areas
Sensitive Areas
Annual Average*
80 µg/m3 60 µg/m3 15 µg/m3 SulphurDioxide (SO2)
24 hours**
120 µg/m3
80 µg/m3 30 µg/m3
Annual Average*
80 µg/m3 60 µg/m3 15 µg/m3 Oxides of Nitrogen as (NO2) 24
hours** 120
µg/m3 80 µg/m3 30 µg/m3
Annual Average*
360 µg/m3
140 µg/m3 70 µg/m3 Suspended Particulate Matter (SPM)
24 hours**
500 µg/m3
200 µg/m3 100 µg/m3
Annual Average*
120 µg/m3
60 µg/m3 50 µg/m3 Respirable Particulate Matter (RPM) (size less than 10 microns) 24
hours** 150
µg/m3 100 µg/m3 75 µg/m3
Annual Average*
1.0 µg/m3 0.75 µg/m3 0.50 µg/m3
Lead (Pb)
24 hours**
1.5 µg/m3 1.00 µg/m3 0.75 µg/m3
Ammonia1 Annual Average*
0.1 mg/ m3
0.1 mg/ m3 0.1 mg/m3
24 hours**
0.4 mg/ m3
0.4 mg/m3 0.4 mg/m3
8 hours**
5.0 mg/m3
2.0 mg/m3 1.0 mg/ m3
Carbon Monoxide (CO)
1 hour 10.0 mg/m3
4.0 mg/m3 2.0 mg/m3
Environmentally Sensitive areas (ESA): landscape, wild life & historical importance
* annual mean of 104 measurements in a year** 24/8 h values should be met 98% of time in a year
NATIONAL AMBIENT AIR QUALITY STANDARDS:2009
Particulate MatterSuspended Particulate Matter
Fine Particulate Matter
• Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.
• These small particles can remain suspended in the air for long periods of time.
• Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with an electron microscope.
What is Particulate Matter?
Sources of Particulate Matter PM10
• Primary Particles– These particles are emitted directly
from air pollution sources such as power plants, factories, automobile exhaust, construction sites, unpaved roads, wood burning etc.
• Secondary Particles– Formed in the atmosphere indirectly
when gases from burning fuels react with sunlight and water vapor and are chemically transformed into particles, secondary pollutants: solid/liquid
Types of Fine Particulate Matter
A few definitions• Solid or liquid particles with sizes from
0.001 – 100 μm may be in air
• General term for these is aerosols
• Dust originates from grinding or crushing
• Fumes are solid particles formed when vapors condense
• Smoke describes particles released in combustion processes
• Smog is used to describe air pollution and is combination of smoke+fog
Hukka
PM2.5
(2.5 µm)PM10
(10µm)
Hair cross section (70 m)
Human Hair (70 µm diameter)
What Is PM10 & PM2.5 ?
Health Effects from Particulate Matter
• Many scientific studies have linked breathing PM to a series of significant health problems, including:– aggravated asthma – increase in respiratory symptoms
like coughing and difficult or painful breathing
– chronic bronchitis – decreased lung function – premature death
Health Effects of Particulate Matter
• Impact depends on particle size, shape and composition
• Large particles trapped in nose• Particles >10 μm removed in
tracheobronchial system• Particles <0.5 μm reach lungs but are
exhaled with air• Particles 2 – 4 μm most effectively get
deposited in lungs
Stokes Law
Aerodynamic diameter: Diameter of the sphere having the same settling velocity as that of the particle
Given by George Gabriel Stokes in 1851
Where,
acceleration of gravity (g), m/s2
particle diameter (d), m
density of particle (ρp), kg/m3
density of medium (ρm), kg/m3
viscosity of medium (μ), kg/m s
Other Effects From Particles• Visibility Impairment
– PM is the major cause of reduced visibility (haze).
• Aesthetic Damage– Soot, a type of PM, stains and
damages stone and other materials, including objects such as monuments and statues.
• Plant Damage– PM can form a film on plant
leaves interfering with photosynthesis and plant growth
Particulate Matter and Taj
The deposition of SPM on the shimmering white marble of the Taj Mahal imparts yellow tinge to the marble surface
Norms CO( g/km) HC (g/km) NOx (g/km) PM(g/km)
1991Norms 14 3.5 18
1996 Norms 11.2 2.4 14.4
India stage 2000 norms
4.5 1.1 8.0 0.36
Bharat stage-II
4.0 1.1 7.0 0.15
Bharat Stage-III
2.1 1.6 5.0 0.10
Bharat Stage-IV
1.5 0.96 3.5 0.02
Emission norms for heavy Diesel vehicles
Indian Emission Standards (4-Wheel Vehicles)
Standard Reference Date Region
India 2000 Euro 1 2000 Nationwide
Bharat Stage II Euro 2 2001 NCR*, Mumbai, Kolkata, Chennai
2003.04 NCR*, 10 Cities†
2005.04 Nationwide
Bharat Stage III Euro 3 2005.04 NCR*, 10 Cities†
2010.04 Nationwide
Bharat Stage IV Euro 4 2010.04 NCR*, 10 Cities†
* National Capital Region (Delhi)
† Mumbai, Kolkata, Chennai, Bangalore, Hyderabad, Ahmedabad, Pune, Surat, Kanpur and Agra
Carbon Monoxide• Most abundant air
pollutant• Produced by incomplete
combustion
– insufficient O2
– low temperature– short residence time– poor mixing
• Major source (~ 77%) is motor vehicle exhaust
Carbon MonoxideMisc10%
Industrial7%
Fuel Combustion6%
Transport77%
Misc
Industrial
Fuel Combustion
Transport
Carbon Monoxide• Colorless and odorless • When inhaled, binds to hemoglobin in blood to form
carboxyhemoglobin, reducing the oxygen carrying capacity• brain function reduced, heart rate increased at lower levels• asphyxiation occurs at higher levels
• % COHb = β(1- e-γt) (CO)
• % COHb = Carboxyhemoglobin as % saturation• CO = Carbon monoxide conc. in ppm• γ = 0.402 h-1
• β= 0.15 %/ ppm CO• t = exposure time in hours
Carbon Monoxide
Carbon Monoxide
• Typical Levels– busy roadways: 5 – 50 ppm– congested highways: up to 100 ppm
Norms CO( g/km) HC (g/km) NOx (g/km) PM(g/km)
1991Norms 14 3.5 18
1996 Norms 11.2 2.4 14.4
India stage 2000 norms
4.5 1.1 8.0 0.36
Bharat stage-II
4.0 1.1 7.0 0.15
Bharat Stage-III
2.1 1.6 5.0 0.10
Bharat Stage-IV
1.5 0.96 3.5 0.02
Emission norms for heavy Diesel vehicles
Sulfur Oxides (SOx)• SO2, SO3, SO4
2 formed during combustion of fuel containing sulfur
• H2S released is converted to SO2
• 10 Tg/yr natural sources
• 75 Tg/yr anthropogenic sources
SOx
Sulfur Dioxide: Health Effects• High concentrations of SO2 can result in
temporary breathing impairment. • Longer-term exposures to high concentrations of
SO2, in conjunction with high levels of PM, include respiratory illness, alterations in the lungs' defenses, and aggravation of existing cardiovascular disease
• Short-term exposures of asthmatic individuals to elevated SO2 levels may result in reduced lung function.
Sulfur Dioxide: Environmental Effects
• Acid Rain Decreased Visibility
Oxides of Nitrogen (NOx)
• Primarily NO and NO2
• NO3, N2O, N2O3, N2O4, N2O5 are also known to occur
• Thermal NOx created by oxidation of atmospheric N2 when T > 1000 K
• Fuel NOx from oxidation of N in fuel
NOx
Transport45%
Misc1%
Industrial4%
Fuel Combustion50%
Misc
Industrial
Fuel Combustion
Transport
Oxides of Nitrogen (NOx)
• NO has few health effects, but is oxidized to NO2
• NO2 irritates lungs and promotes respiratory infections
• NO2 reacts with hydrocarbons in presence of sunlight to produce smog
• NO2 reacts with hydroxyl radicals to produce nitric acid – acid precipitation
Lead
• Sources:– gasoline (historical)– metals processing
• Highest air Pb concentrations – in the vicinity of
nonferrous and ferrous smelters, and battery manufacturers.
Pb
Lead: Health Effects
• Accumulates in the blood, bones, and soft tissues.
• Adversely affects the kidneys, liver, nervous system, and other organs.
• Excessive exposure to Pb may cause neurological impairments, such as seizures, mental retardation, and behavioral disorders.
• May be a factor in high blood pressure and subsequent heart disease.
Photochemical Smog
hydrocarbons + NOx + sunlight → photochemical smog (oxidants)
• primary oxidants produced:
– ozone (O3)
– formaldehyde– peroxyacetyl
nitrate (PAN)
Ozone depletion mechanism
• Different chemicals are responsible for the destruction of the ozone layer
• Topping the list :– chlorofluorocarbons (CFC’s) – man-made, non-toxic and inert in the troposphere– In the stratosphere are photolysed, releasing reactive chlorine
atoms that catalytically destroy ozone
Photochemical Smog
Photochemical Smog
Ozone: Health Effects
• Increased incidents of respiratory distress.
• Repeated exposures to ozone:– Increased susceptibility to respiratory
infection– Lung inflammation– Aggravation of pre-existing respiratory
diseases such as asthma. – Decrease in lung function and increased
respiratory symptoms such as chest pain and cough.
Ozone: Environmental Effects• Ozone also affects
vegetation and ecosystems– reductions in agricultural and
commercial forest yields ($0.5 billion/yr in US alone)
– reduced growth and survivability of tree seedlings
– increased plant susceptibility to disease, pests, and other environmental stresses (e.g., harsh weather).
Ozone Revised Standards
• In 1997, the 1-hour ozone standard of 0.12 parts per million (ppm) was replaced with a new 8-hour 0.08 ppm standard.
Units of Measurement
• μg/m3 – mass:volume• parts per million (ppm) – volume:volume
where C = concentration in μg/m3
3
-1
L/m
kPa/ K molL
1000
325.101273/414.22 22
MW
PTCppm
Landmark datelines to capital clean
• April 1995: Mandatory fitting of catalytic convertors• April 1996: Low sulphur diesel introduced• April 1998: Introduction of CNG buses in Delhi• Sept 1998: Complete removal of lead in petrol• Dec 1998: Restrict plying of goods vehicles during the
day• Sept 1999: Amendment of Motor Vehicles Act to
include CNG• April 2000: Private vehicles to be registered only if
they conform to Euro II standards• April 2000: Eight-year-old commercial vehicles
phased out• Nov 2002: Conversion of all public transport buses to
CNG