Chapter 17Air Pollution• Natural Sources

– Volcanoes– Deserts – Decomposition

• Human Sources– Auto Emissions – Power Plant Emissions – Chemical Plant Emissions

• The Difference– Human Sources can be controlled and prevented, natural

sources cannot.

Chapter 17

Why is Air Pollution a Concern?

• Gravity tends to hold denser gasses close to Earth’s surface, many pollutants are fairly dense so…

• Well known examples of deadly episodes– London, Eng: 4000 killed– Donora, PA: 17 killed 5900 sick

• Chronic Issues, too– Mexico City: 6400 death each year

Chapter 17Primary Air Pollutants –5 types• Carbon Monoxide (CO)

– Causes—incomplete combustion of gas, coal, wood trash, etc

– Largest source is Automobile– 2nd Largest Tobacco Smoke– Small concentrations can result in death

• 0.001% for several hours is enough

– Not persistent

• HydroCarbons– Causes—incomplete combustion, evaporation from fuel

—automobiles, refineries, industries.– Engine modifications help

Chapter 17• Particulates <10 microns

– Very small pieces of solids– Causes—particles from fire, asbestos from

brakes, dust/ash from industry– Aesthetic/Cancer Causing– Accumulate or carrier

• Sulfur Dioxide (SO2)– Causes—burning of fossil fuels with S– Irritate lungs and forms acids when mixed

• 1306 London banned use of S rich coals• 1952 inversion of S rich air poll. kills 4000

Chapter 17

• Oxides of Nitrogen (NOx, NO, NO2)– Causes—automobile– Catalytic converters help– Involved in production of Photochemical Smog

Secondary Air Pollutants

• Photochemical Smog – Interaction of NOx with UV light– Results in ground level ozone– Usually reddish-brown haze

Chapter 17– Ground Level Ozone formation

• Rush hour N2 +O2 -> 2NO• + atmospheric O2 2NO+O2 -> 2NO2• + UV light NO2 +UV ->NO + O• + atmospheric O2 O2 + O -> O3

– Ozone is oxidizer and highly reactive• Reacts with living tissue

– Lungs– Chlorophyll in plants

– Geography and climate influence formation– Valley ringed by mountain—bad– Solution—get rid of IC cars or move city

Chapter 17

• Other air pollutants– Lead– Toxics– Radon

• Control of Air Pollution– Solutions depend on willingness of

governments, industry and individuals to make changes

• Pollution control in cars

• Particulates

• SOx

Chapter 17• The Clean Air Act (1967, rev 70,77, 90)• 4 Categories of programs

– 1. All new/existing sources are subject to ambient air quality regs.

– 2. New sources subject to more stringent control technology and permitting

– 3. Control of specific pollution problems including haz. Air emissions and visisbility impairment

– 4. Comprehensive permit program

• Air quality standards for SO2, NOx, particulates, CO, O3, and lead

• State responsibility for implementing SIPs

Chapter 17

The Clean Air Act (cont’d)

• Ways to go but program has been successful

• Emissions of 6 worst pollutants down 33%

• Benefits outweigh costs by 40 to 1

• Still, smog may affect 6 million asthmatics and may send 160,000 people to emergency room each year

Chapter 17Acid Rain• Acid deposition can be natural or man-made

– Volcanoes, vegetation, lightning– Coal burning, automobiles

• Can be wet or dry– Wet with rain or snow– Dry with settling of particles– All processes called ACID RAIN

• Effects– Aesthetics on buildings/monuments– Forests, aquatic ecosystems, soil, etc– Not as big an issue in Texas as NE US and Canada

Chapter 17Global Warming

• Lots of unknowns but many agree it is potential future reality with human causes

• How does it work?– Greenhouse gasses allow sunlight to pass through

but reflect/absorb resulting heat energy from earth.– CO2 is most abundant GH gas

• Increase from 315 ppm to 362 ppm in 40 years

• Can counter with increases in energy efficiency and uptake/sequestration.

Chapter 17

Global Warming (cont’d)

• Chlorofluorocarbons (CFC)• Small amounts released but highly effective

• 15,000 times that of CO2

– Banned for most part in US, Canada, Europe– Releases are expected to continue to decline– Major effects on ozone layer

• Methane and NO– Also involved in global warming but limited

ability to control releases

Chapter 17Effects of Global Warming• Worsening Health Effects

– Exacerbate smog/ground level ozone– More disease/wider range of disease/vectors– More heat more heart attacks etc

• Rising Sea Level– Loss of coastal land– More flooding

• Disruption of Water Cycle– Greater Droughts/Floods

• Changing Forests and Natural Areas– Range Shifts by 300 miles– Change in composition

Chapter 17Effects of Global Warming (cont’d)• Challenges to Agriculture/Food Supply

– May increase yields in some areas– Increase irrigation demand too– Can likely cope with changes

• Many unknown effects• Feedback loops on global cycle?• Politics and Economics will ultimately

decide our contribution to reduce global warming

Chapter 17

Ozone Depletion• Ozone is O3• Absorbs harmful effects of UV radiation high up

in atmosphere– 99% of UV light is prevented from reaching earth

• Prevents cancer, cataracts and mutations

• CFCs destroy ozone and prevent reforming– 20-30 yrs to reach upper atmosphere– Can react for up to 120 yrs

• Ozone depletion will worsen well into next century based on prior releases