Earth’s Changing Earth’s Changing EnvironmentEnvironment

Lecture 2Lecture 2

Air PollutionAir Pollution

““Those who contemplate the beauty of the earth Those who contemplate the beauty of the earth find reserves of strength that will endure as long as find reserves of strength that will endure as long as life lasts.”life lasts.”

- Rachel Carlson- Rachel Carlson

The AtmosphereThe Atmosphere NN22 780900 ppm780900 ppm (78.09%)(78.09%) OO22 209400 ppm209400 ppm (20.94%)(20.94%) ArgonArgon 9300 ppm 9300 ppm (0.93 %)(0.93 %) COCO22 372 ppm372 ppm (0.037%)(0.037%) Everything else is less than 0.003 % or 30 ppmEverything else is less than 0.003 % or 30 ppm

Layers of the AtmosphereLayers of the Atmosphere

Stratosphere Stratosphere begins at about begins at about 10 miles above 10 miles above the surface.the surface.

Pressure drops Pressure drops with altitude.with altitude.

So, less oxygen So, less oxygen with altitude. with altitude.

Air Pollution – SourcesAir Pollution – Sources

Most air pollution is Most air pollution is emitted from fixed and emitted from fixed and mobile sources at ground mobile sources at ground level. level.

Buoyant ForceBuoyant Force The density of air The density of air

is proportional to is proportional to its Temperature.its Temperature.

Hot polluted air Hot polluted air is less dense is less dense than the cooler than the cooler air around it.air around it.

So, hot polluted So, hot polluted air will rise, air will rise, expand, cool, expand, cool, and disperseand disperse

Temperature vs. AltitudeTemperature vs. Altitude Hot air released at Hot air released at

ground level will loose ground level will loose temperature as it rises temperature as it rises and expands. The rate at and expands. The rate at which its temperature which its temperature drops is the drops is the adiabatic adiabatic lapse rate (ALR) and lapse rate (ALR) and equals 3.5F per 1000 equals 3.5F per 1000 feetfeet. .

The The environmental lapse rateenvironmental lapse rate (ELR) is (ELR) is typically equal to the ALR.typically equal to the ALR.

Unstable AirUnstable Air

If the ELR > ALR, then If the ELR > ALR, then hot polluted air will hot polluted air will rise and disperse.rise and disperse.

Temperature InversionTemperature Inversion If the there is a If the there is a

temperature inversion (a temperature inversion (a warm layer above the warm layer above the cool surface layer), the cool surface layer), the air will not rise. air will not rise.

This may lead to a severe This may lead to a severe pollution episode.pollution episode.

Temperature inversions Temperature inversions are frequently caused by are frequently caused by radiative cooling of the radiative cooling of the ground at night.ground at night.

Subsidence InversionSubsidence Inversion Descending air compresses and Descending air compresses and

warms, creating an inversion warms, creating an inversion layer layer

Global Air CirculationGlobal Air Circulation

The combination The combination of air density, of air density, uneven solar uneven solar heating, and the heating, and the Earth’s rotation Earth’s rotation explains global air explains global air circulation and circulation and climate zones.climate zones.

Hadley CellsHadley Cells

PollutantsPollutants Gases – CO, SOGases – CO, SOxx, O, O33, NO, NOxx, and VOC, and VOC SPM (suspended particulate matter) – SPM (suspended particulate matter) –

particulates and aerosolsparticulates and aerosols

Primary vs. SecondaryPrimary vs. Secondary

COCO Primarily due to auto emissions.Primarily due to auto emissions.

SOSO22

Primarily from power plants: coal and Primarily from power plants: coal and oil.oil.

VOCVOC In rural areas, natural sources dominate.In rural areas, natural sources dominate. In urban areas, transportation dominates.In urban areas, transportation dominates.

NONOxx Primarily from power plants and transportationPrimarily from power plants and transportation Emitted as NO and oxidized to NOEmitted as NO and oxidized to NO22

ParticulatesParticulates From Industry, power plants, and From Industry, power plants, and

transportationtransportation

Photochemical SmogPhotochemical Smog Main harmful Main harmful

ingredient in smog ingredient in smog is ozone. is ozone.

Ozone is formed Ozone is formed when UV radiation, when UV radiation, high temperatures, high temperatures, Nitrogen oxides, Nitrogen oxides, and VOCs combine. and VOCs combine.

Automobiles are Automobiles are the main problem.the main problem.

OzoneOzone Ozone is primarily a Ozone is primarily a

summer problem in summer problem in the US.the US.

Higher temperatures Higher temperatures and higher ozone and higher ozone levels are need to levels are need to drive the reactions.drive the reactions.

VOCs have many VOCs have many sources.sources.

NOx is primarily NOx is primarily from cars.from cars.

Acid RainAcid Rain Acid rain is formed from SO2 and NO2 Acid rain is formed from SO2 and NO2

pollution.pollution.

Acid RainAcid Rain

Sulfuric acid (HSulfuric acid (H22SOSO44) and nitric ) and nitric (HNO(HNO33) acid are formed and ) acid are formed and precipitated on vegetation in lakes precipitated on vegetation in lakes and streams.and streams.

pHpH

Normal rainwater is slightly acid Normal rainwater is slightly acid because of carbonic acid (Hbecause of carbonic acid (H22COCO33) ) and nitric (HNOand nitric (HNO33). pH =5.6). pH =5.6

pH values between 4.0 and 4.5 are pH values between 4.0 and 4.5 are common in NE, Canada, northern common in NE, Canada, northern EuropeEurope

Health Effects:Health Effects: Outdoor Air Pollution Outdoor Air Pollution

Kills 200,000 - 570,000 annually globally.Kills 200,000 - 570,000 annually globally. Kills 20,000 people annually in US.Kills 20,000 people annually in US. Particulates and ozone are the biggest problemParticulates and ozone are the biggest problem Major sources are coal-burning power plants and Major sources are coal-burning power plants and

vehicle emissionsvehicle emissions

Worse Air Pollution DisasterWorse Air Pollution Disaster London, England, 1952London, England, 1952 From December 5 to 8, 1952From December 5 to 8, 1952 The meteorological conditions were ideal for a pollution. Anti-cyclonic or high pressure weather The meteorological conditions were ideal for a pollution. Anti-cyclonic or high pressure weather

with stagnating continental polar air masses trapped under subsidence inversions produced a with stagnating continental polar air masses trapped under subsidence inversions produced a shallow mixing layer with an almost complete absence of vertical and horizontal air motion.shallow mixing layer with an almost complete absence of vertical and horizontal air motion.

Fireplaces and industries supplied the hygroscopic condensation nuclei into the air to form Fireplaces and industries supplied the hygroscopic condensation nuclei into the air to form dense fog. dense fog.

Deaths from bronchitis increased by a factor of 10, influenza by 7, pneumonia by 5, Deaths from bronchitis increased by a factor of 10, influenza by 7, pneumonia by 5, tuberculosis by 4.5, other respiratory diseases by 6, heart diseases by 3 and lung cancer by 2. tuberculosis by 4.5, other respiratory diseases by 6, heart diseases by 3 and lung cancer by 2.

4,000 Londoners perished.4,000 Londoners perished.

Health Effects:Health Effects: Indoor Air Pollution - Global Indoor Air Pollution - Global

Kills 2.8 million annual globallyKills 2.8 million annual globally In developing countries, burning wood and In developing countries, burning wood and

other materials for heat and cooking is the other materials for heat and cooking is the major source. major source.

Health Effects:Health Effects:Indoor Air Pollution - USIndoor Air Pollution - US

Kills 100,000 people annually in US.Kills 100,000 people annually in US. Cigarette smoke, formaldehyde, and Cigarette smoke, formaldehyde, and

radon-222 are primary indoor pollutants.radon-222 are primary indoor pollutants.