Chapter 15

Air Pollution

Layers of Atmosphere Review

Structure of the Atmosphere• Troposphere:

– All weather confined here– Temp. decreases as altitude increases

– 78% N2 & 22% O2

– Ozone (O3) in troposphere = bad!!

• Stratosphere:– Temp increases with altitude (temp inversion)

– UV absorbing O3 (ozone) = good!!!• UVA, UVB and UVC• sunburn, skin/eye cancer, cataracts

• Keeps O2 in troposphere

Air Pollution• Introduction of chemical, particulate matter, or

microorganisms into atmosphere @ concentrations high enough to harm plants, animals, & alter ecosystems.– Refers to pollutants in troposphere (aka “Ground

Level Pollution”• Most polluted areas: Asia (outdoor) & Asia, Africa, & SA

(indoor)

– Natural (fires & volcanoes) or anthropogenic (cars & factories)

– Global system: atmosphere envelops the whole globe• Acid rain in W. Coast of US from Asia

Primary & Secondary Pollution• Primary: pollutants that come directly out of the

smokestack, exhaust pipe, or natural emission source.– Ex: CO, CO2, SO2, NOX, suspended particulate

matter & VOC

• Secondary: primary pollutants that have undergone transformation in the presence of sunlight, water, oxygen, or other compounds.– Ex: Ozone (O3), SO4

2-, NO3-

– Reduce the primary pollutant to reduce the secondary pollutant.

Major Air Pollutants• Sulfur dioxide (SO2) or (SOx):

– 1/3 SO2 occurs naturally through the sulfur cycle.

– 2/3 from human sources• Combustion of sulfur fuels (oil, coal, gasoline)

– Respiratory Irritant, harms plant tissue, forms sulfuric acid

– Secondary Pollution:• SO2 + O2 SO3

• SO3 + H2O H2SO4

– Acid deposition – harms terrestrial and aquatic life

Nitrogen oxides (NOX) : N2 + O2 2NO

2NO + O2 2NO2

• Combustion of fossil fuels, biomass• NO can also form from lightning and certain soil

bacteria.Respiratory irritant, precursor to ozone and nitric

acid, NO3- (over fertilization of terrestrial and aquatic ecosystems)

Secondary: • 3NO2 + H20 2 HNO3 + NO

• NO2 +UV NO + O O+O2 O3

• Carbon oxides: – Carbon monoxide (CO)

• toxic gas (suffocation)• during the incomplete combustion of carbon compounds• cigarette smoke

– Carbon dioxide (CO2)• 93% natural carbon cycle

• 7% of CO2 from human activities (mostly burning fossil fuels).

• greenhouse gas – climate effects• Acidification of aquatic systems• not considered a pollutant by government standards

– Most harmful forms of SPM • fine (PM < 10); written as PM10

• **Ultrafine (PM 2.5); written as PM2.5

– Volcanoes, coal power plants, road dust, vehicle exhaust, wood fires

– 60,000 premature deaths a year in the U.S.• increases cardiovascular/respiratory disease

• decreased lung function

Suspended particulate matter (SPM):

Major Air Pollutants

• Lead (Pb):– Gasoline (leaded), coal, paint

– Incineration - solder on electronics, plastics, car batteries, ammunition

– Impairs CNS: • Impairs concentration and behavior

Major Air Pollutants

Ozone (O3):Increased NOx increases ozone in tropo

Decreased ozone in stratosphere = UVB and C in troposphere

Is a highly reactive gas that is a major component of photochemical smog.

It can • Cause and aggravate respiratory illness.• Can aggravate heart disease.• Damage plants, rubber in tires, fabrics, and paints.

• Volatile organic compounds (VOCs):– Most are hydrocarbons that emit vapors

• Gasoline, lighter fluid, dry cleaning fluid, oil based paints, methane, perfumes

– Conifer trees– CFC’s (from aerosols & refrigerants)– Industrial solvents such as TCE, benzene and

vinyl chloride• Long-term exposure to benzene and TCE

carcinogenic, blood disorders and immune system effects

• Vinyl Chloride – analgesic, carcinogenic – Usually an intermediate compound (PVC)

– All VOC’s whether toxic or not are precursors to photochemical smog

Major Air PollutantsRadon (Rn):•Is a naturally occurring radioactive gas found in some types of soil and rock.•It can seep into homes and buildings sitting above such deposits.•15% of lung cancer deaths

Major Air Pollutants

Mercury (Hg, methyl mercury)•Burning of coal, gold mining, cement manufacturing•Incineration - barometers, appliance, batteries, jewelry, pesticides, paint, cf light bulbs, dental filling•Soil erosion, volcanoes, rock erosion•CNS – inhibits neuron and mitochondria function •Bioaccumulation/Biomagnification

The

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URBAN OUTDOOR AIR POLLUTION

• Photochemical Smog• Temperature

Inversions• Acid Deposition

LONDON, mostly automobiles

Photochemical Smog• Photochemical oxidants:

– Includes O3

– Pollutants formed when NOX & SOX react with sunlight

• Smog:– O3 reacts with VOC & NOX to more dangerous

photochemical oxidants

– SOX & NOX reacts with photochemical oxidants to form some particulates

– Mixture of oxidants & particulate matter is referred to as smog.

Smog Categories• Los Angeles-type smog:

– Dominated by oxidants & O3

– AKA “brown smog”

• London-type smog:– Sulfurous smog or gray smog– Dominated by SO2 & sulfate compounds

• Atmospheric Brown Cloud:– Derived from fossil fuel combustion & burning

biomass– Found mostly is Asia

Sunlight plus Cars Equals Photochemical Smog

• Photochemical smog – air pollutants formed by the reaction of nitrogen

oxides and volatile organic hydrocarbons under the influence of sunlight. Warm temps expedite chemical reactions.

Case Study: South Asia’s Massive Brown Cloud

• Coal Burning Countries– China and India– Pollution stretches over much

of southeastern Asia.– Reduced photosynthesis and

crop interference.– Fine particles and droplets in

the cloud appear to be changing regional climates (including rainfall).

• May have contributed to floods in 2002 and 2005 which killed thousands of people.

Thermal Inversions

• This occurs when a warm layer of mid-altitude air traps cooler air below.

• The warm inversion layer traps emissions beneath it causing a severe pollution event.

Thermal Inversions

• Subsidence Inversion:– Cold, cloudy weather in a valley surrounded by mountains

can trap air pollutants (left). LA?

• Radiation Inversion: – climate, light winds, mountains on three sides and an

ocean on the other (right) are susceptible to inversions. LA?

Factors Influencing Levels of Outdoor Air Pollution

• Outdoor air pollution can be reduced by:– settling out, precipitation, sea spray, winds, and

chemical reactions.

• Outdoor air pollution can be increased by:– urban buildings (slow wind dispersal of

pollutants), mountains (promote temperature inversions), and high temperatures (promote photochemical reactions).

ACID DEPOSITION

• Formation:– NOX & SO2 are transformed by water & O2 into

secondary pollutants of nitric acid & sulfuric acid.

– Reactions occur over a number of days & pollutants can travel 1,000 km

– Washed out of air by precipitation & deposited on vegetation, soil, or water

ACID DEPOSITION

• Acid deposition consists of rain, snow, dust, or gas with a pH lower than 5.6.

Figure 19-6Figure 19-6

ACID DEPOSITION

• pH measurements in relation to major coal-burning and industrial plants.

Figure 19-7Figure 19-7

ACID DEPOSITION

• Acid deposition contributes to chronic respiratory disease and can leach toxic metals (such as lead and mercury) from soils and rocks into acidic lakes used as sources for drinking water.

ACID DEPOSITIONSoil Acidification

Leaching of Heavy Metals

Damage to Bark and Leaves

Reduced Photosynthesis

Tree Death

Figure 19-9Figure 19-9

Fig. 19-10, p. 452

Solutions

Acid Deposition

Prevention Cleanup

Reduce air pollution by improving energy efficiency

Add lime to neutralize acidified lakes

Reduce coal use

Add phosphate fertilizer to neutralize acidified lakes

Increase natural gas use

Increase use of renewable energy resources

Burn low-sulfur coal

Remove SO2 particulates & NOx from smokestack gases

Remove NOx from motor vehicular exhaust

Tax emissions of SO2

PREVENTING AND REDUCING AIR POLLUTION

• The Clean Air Acts in the United States have greatly reduced outdoor air pollution from six major pollutants:– Carbon monoxide– Nitrogen oxides– Sulfur dioxides– Lead– Ozone– Suspended particulate matter (less than PM-10)

• Decrease by 41% while GDP raised by 64%

PREVENTING AND REDUCING AIR POLLUTION

Environmental scientists point out several deficiencies in the Clean Air Act:The U.S. continues to rely on cleanup rather

than prevention.The U.S. Congress has failed to increase fuel-

efficiency standards for automobiles.Regulation of emissions from motorcycles and

two-cycle engines remains inadequate.There is little or no regulation of air pollution from

oceangoing ships in American ports.

PREVENTING AND REDUCING AIR POLLUTION

– Airports are exempt from many air pollution regulations.

– The Act does not regulate the greenhouse gas CO2.

– The Act has failed to deal seriously with indoor air pollution.

– There is a need for better enforcement of the Clean Air Act.

Using the Marketplace to Reduce Outdoor Air Pollution

To help reduce SO2 emissions, the Clean Air Act authorized and emission trading (cap-and-trade) program.Enables the 110 most polluting power plants to

buy and sell SO2 pollution rights.

Between 1990-2002, the emission trading system reduced emissions.

In 2002, the EPA reported the cap-and-trade system produced less emission reductions than were projected.

Solutions: Reducing Outdoor Air Pollution

• There are ways to prevent and control air pollution from coal-burning facilities.– Electrostatic precipitator: are used to attract

negatively charged particles in a smokestack into a collector.

– Wet scrubber: fine mists of water vapor trap particulates and convert them to a sludge that is collected and disposed of usually in a landfill.

– Baghouse Filter: Air passes through fabrics that can remove almost 100% of PM emissions

Electrostatic Precipitator

Uses electrical charge to attract particlesCan remove 99% of particulate matterDoes not remove hazardous ultrafine

particles.Produces toxic dust that must be safely

disposed of.Uses large amounts of electricity

The ScrubberAKA the “Wet Scrubber”Can remove 98% of SO2 and particulate

matter.Not very effective in removing hazardous

fine and ultrafine particles.Uses water and electricity to catch

particulate matter and SO2

The Baghouse Filter

Fig. 19-17, p. 459

Solutions

Stationary Source Air Pollution

Prevention

Burn low-sulfur coal

Disperse emissions above thermal inversion layer with tall smokestacks

Remove sulfur from coal

Convert coal to a liquid or gaseous fuel

Remove pollutants after combustion

Shift to less polluting fuels

Tax each unit of pollution produced

Dispersion or Cleanup

Solutions: Reducing Outdoor Air Pollution

• In 2003, fourteen states and a number of U.S. cities – sued the EPA to block new rules that would allow

older coal-burning power plants to modernize without having to install the most advanced air pollution controls.

Stratospheric Ozone

• Ultra-violet Radiation: – UV-A, UV-B, UV-C in order of increasing

energy• UV-A – contributes to and possibly initiates skin

cancer• UV-B & UV-C can cause significant damage to

tissue and DNA of a living organism

– However . . . • Layer of O3 & O2 in stratosphere absorbs 99% of

all incoming UV-B & UV-C radiation

Stratospheric Ozone• Forms & breaks down naturally in a closed –loop

cycle.• Formation of stratospheric ozone:

– O2 + UV-C

– In the presence of UV radiation, oxygen is converted into ozone

• Ozone is broken down into O2 and free oxygen atoms when it absorbs both UV-C & UV-B radiation– O3 + UV-B or UV-C

– This maintains a steady-state conc. of O3

Anthropogenic Contributions to Ozone Destruction

• Certain chemicals are catalyst to breaking down ozone . . . . The most important is chlorine atoms.

• CFC’s (chlorofluorocarbons):– Used in AC, refrigerators, aerosols, &

injecting air into foam products– When reaches stratosphere, UV radiation

breaks bond connecting Cl to CFC molecule

CFC’s & Ozone Destruction

• Free chlorine atom reacts with ozone:– O3 + Cl ClO + O2 (destroying it)

• Next a free oxygen pulls the oxygen atom from the ClO, freeing the Cl. The free chlorine atom is ready to break down more ozone.– ClO + O Cl + O2

– One Cl atom can breakdown as many as 100,000 ozone molecules

Ozone Depleting Chemicals

Chlorofluorocarbons (CFCs)Chlorofluorocarbons (CFCs)

HalonsHalonsMethyl bromideMethyl bromideCarbon tetrachlorideCarbon tetrachlorideMethyl chloroformMethyl chloroformHydrogen chlorideHydrogen chlorideSources of CFCsSources of CFCs

Seasonal Thinning at the Poles

Ozone thinning (hole)Ozone thinning (hole) Polar vortexPolar vortex

Fig. 18-30 p. 475Fig. 18-30 p. 475

Reasons for Concern Increased incidence and severity of sunburn Increased incidence and severity of sunburn

Increase in eye cataracts Increase in eye cataracts

Increased incidence of skin cancer Increased incidence of skin cancer

Immune system suppression Immune system suppression

Increase in acid deposition Increase in acid deposition

Lower crop yields and decline in productivity Lower crop yields and decline in productivity

Increase in tropospheric ozone Increase in tropospheric ozone

• http://www.casadefrias.com/2011/12/my-response-to-dear-16-year-old-me-skin.html

Solutions: Protecting the Ozone Layer

CFC substitutes: citrus-based solventsCFC substitutes: citrus-based solvents

Technofixes Technofixes

Montreal Protocol (1987)Montreal Protocol (1987)

Fig. 18-33 p. 479Fig. 18-33 p. 479

Ozone in stat has stabilized to 5 ppb & should fall to about 1 ppb by 2100

INDOOR AIR POLLUTION

INDOOR AIR POLLUTIONIndoor air pollution usually is a greater threat

to human health than outdoor air pollution.According to the EPA, the four most

dangerous indoor air pollutants in developed countries are:Tobacco smoke.Formaldehyde.Radioactive radon-222 gas.Very small fine and ultrafine particles.

Chloroform

Benzo--pyrene

Styrene

Radon-222

Methylene Chloride

Tobacco Smoke

Carbon Monoxide

Asbestos

Nitrogen Oxides

1, 1, 1-Trichloroethane

Particulates

FormaldehydeTetrachloroethylenePercholoroethylene

Para-dichlorobenzene

Fig. 19-11, p. 453

INDOOR AIR POLLUTION• Household dust mites

that feed on human skin and dust, live in materials such as bedding and furniture fabrics.– Can cause asthma

attacks and allergic reactions in some people.

Figure 19-12Figure 19-12

INDOOR AIR POLLUTIONDEVELOPING NATIONS~ 3 billion people cook and heat their homes using open fires and leaky stoves burning biomass (wood, animal dung and crop waste) and coal.2 million people die prematurely from illness attributable to indoor air pollution from household solid fuel use.50% of pneumonia deaths among children under five are due to particulate matter inhaled from indoor air pollution.>1 million people a year die from chronic obstructive respiratory disease (COPD) that develop due to exposure to such indoor air pollution.

women and men exposed to heavy indoor smoke are 2-3 times more likely to develop COPD.

HEALTH EFFECTS OF AIR POLLUTION

• Your respiratory system can help protect you from air pollution, but some air pollutants can overcome these defenses. Figure 19-14Figure 19-14

HEALTH EFFECTS OF AIR POLLUTION

Normal human lungs (left) and the lungs of a person who died of emphysema (right).

Figure 19-15Figure 19-15

Air Pollution is a Big Killer

• Each year, air pollution prematurely kills about 3 million people, mostly from indoor air pollution in developing countries.– In the U.S., the EPA estimates that annual

deaths related to indoor and outdoor air pollution range from 150,000 to 350,000.

– According to the EPA, each year more than 125,000 Americans get cancer from breathing diesel fumes.

Air Pollution is a Big Killer

• Spatial distribution of premature deaths from air pollution in the United States.

Figure 19-16Figure 19-16

Solutions: Reducing Outdoor Air Pollution

• There are a of ways to prevent and control air pollution from motor vehicles.– Because of the Clean Air Act, a new car today in

the U.S. emits 75% less pollution than did pre-1970 cars.

– There is and increase in motor vehicle use in developing countries and many have no pollution control devices and burn leaded gasoline.

Fig. 19-19, p. 460

Solutions

Motor Vehicle Air Pollution

Prevention Cleanup

Emission control devices

Mass transit

Bicycles and walking

Less polluting engines

Less polluting fuels

Improve fuel efficiency

Car exhaust inspections twice a year

Get older, polluting cars off the road

Give buyers large tax write-offs or rebates for buying low-polluting, energy efficient vehicles

Stricter emission standards

Indoor Air Pollution

• Not much is done to mitigate indoor air pollution

• Bigger threat to human health than outdoor air pollution.

• Health scientists call for us to focus on preventing air pollution (especially indoor) in developing countries.

Fig. 19-20, p. 461

Solutions

Indoor Air Pollution

Prevention

Cover ceiling tiles & lining of AC ducts to prevent release of mineral fibers

Use adjustable fresh air vents for work spaces

Increase intake of outside airBan smoking or limit it to well ventilated areas

Change air more frequently

Set stricter formaldehyde emissions standards for carpet, furniture, and building materials

Circulate a building’s air through rooftop green houses

Prevent radon infiltration Use exhaust hoods for stoves and appliances burning natural gasUse office machines in well

ventilated areas

Use less polluting substitutes for harmful cleaning agents, paints, and other products

Install efficient chimneys for wood-burning stoves

Cleanup or Dilution

Fig. 19-21, p. 461

What Can You Do?

Indoor Air Pollution

• Test for radon and formaldehyde inside your home and take corrective measures as needed.

• Do not buy furniture and other products containing formaldehyde.

• Remove your shoes before entering your house to reduce inputs of dust, lead, and pesticides.

• Test your house or workplace for asbestos fiber levels and for any crumbling asbestos materials if it was built before 1980.

• Don't live in a pre-1980 house without having its indoor air tested for asbestos and lead.

• Do not store gasoline, solvents, or other volatile hazardous chemicals inside a home or attached garage.

• If you smoke, do it outside or in a closed room vented to the outside.

• Make sure that wood-burning stoves, fireplaces, and kerosene- and gas-burning heaters are properly installed, vented, and maintained.

• Install carbon monoxide detectors in all sleeping areas.