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Air Quality

Virendra Sethi

vsethi@iitb.ac.in

7809

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• Film : Future Car (Discovery Channel)

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ES 403 Environmental Studies

Air Quality• Question 1 : What is AIR POLLUTION ?

• Question 2 : What is your role in contributing to protection of Air Quality as

(a) A good citizen ?

(b) An Engineer/Scientist ?

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What is Air Pollution ?

• Perception– Visible– Odour

• What is clean air ?– 78% Nitrogen + 21% Oxygen + 1% Trace

– 340 ppm CO2 (0.034%)

• Water – Heat Released/Absorbed

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Lifecycles/Statistics

• Capacity of the earth system as a sink– Feasibility (thermodynamics)– Proximity

• Characteristic times– Kinetics– Sulphur, Carbon, Nitrogen, Halogen Containing

Compounds Cycles

• Statistics

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Scales

• Local > Regional > Global

• Earth : Apple :: Atmosphere : Skin

• Ambient : Indoor

• Dispersion and Mixing

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Class Exercise

• How many grams of Sulphur, if burnt in PC Saxena Auditorium, would pose a health risk to you ?

• Given : Regulatory Limit for SO2 in Ambient Air is – 80g/m3 (0.03 ppm) for annual average– 1300 g/m3 (0.5 ppm) for 3 hour average

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How do we manage Air Quality ?

• At the source itself– Industry– Vehicles– Dust– Home cooking

• After the source– Dispersion and Mixing

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Mixing/Dispersion

• Meteorology– Vertical

• Temperature– Lapse Rate

– Horizontal• Wind

– Speed – Direction

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Dispersion – Gaussian Plume

WIND

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Wind Rose

http://www.epa.gov/ttn/naaqs/ozone/areas/wind.htm#dlfi

1 knot = 1.82 km/hr

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• Wind roses are divided into 16 wind directions

• Each wind direction is divided into wind speeds

• As the percent of time the wind blows from a particular directions gets larger, the portion of the bar representing the wind speed gets larger both in length and width

14http://www.ldeo.columbia.edu/edu/dees/ees/climate/slides/atmprofile.gif

COMING SOON

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Lapse Rates

• Atmosphere cools with height– What rate ?

• Dry (Adiabatic) 10°C/km• Wet (Adiabatic) 6°C/km

– (Release of heat with condensation)

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ACTUAL

ADIABATIC (1°C/100 m)

1000 m (say)

20 °C19 °C18 °C

20 °C Air Parcel

19 °C Air Parcel at 1100 m

1100 m

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ADIABATIC (1°C/100 m)

1000 m (say)

20 °C 21°C 22 °C

20 °C Air Parcel

21 °C Air Parcel at 1100 m

1100 m

900 m

ACTUAL

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ADIABATIC (1°C/100 m)

1000 m (say)

20 °C19.5 °C19°C

20 °C Air Parcel

19 °C Air Parcel at 1100 m

1100 m

ACTUAL

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WIND

Adiabatic

Actual

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ScenariosAdiabatic

ActualH

eig

ht

Temperature

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ScenariosAdiabatic

ActualH

eig

ht

Temperature

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ScenariosAdiabatic

ActualH

eig

ht

Temperature

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Stability

http://www.tpub.com/content/aerographer/14312/css/14312_47.htm

Wet Lapse Rate

Dry Lapse Rate

Average

Unstable

Stable

Height

Temperature

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Match the profile

Unstable

Stable

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Review

Dispersion and Mixing Influenced by :• Wind

– Speed– Direction– Wind Rose

• Temperature Lapse Rates– Dry adiabatic– Wet Adiabatic– Stability

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Smog Inc.

• Short Film (26 minutes)

• Centre for Science and Environment, NGO