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The Atmosphere-

Air And Air Pollution

APES

Spring 2014

The Atmosphere

• Thin layer of gases that envelops Earth.

– Held near the surface by gravitation and pushed

upward by thermal energy.

– Primarily nitrogen (78%), oxygen (21%), argon

(0.9%), carbon dioxide (0.03%) and water vapor.

– Trace amounts of other gases/pollutants

– Dynamic system

Structure of the Atmosphere

• Made up of several vertical layers

– Troposphere- bottom layer

• Where weather occurs

• Temperature decrease w/ elevation

• At the top is tropopause- acts as a lid

– Stratosphere- above the troposphere

• Stratospheric ozone layer just above the tropopause

• Protects again UV radiation

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Atmospheric Processes • Atmosphere moves because of the Earth’s rotation and

differential heating.

• Produce global patterns of prevailing winds and

latitudinal belts of high and low pressure

– Significant in distribution of pollutants

Stationary Source of Air Pollution • Stationary sources are those that have a relatively fixed

location.

– Point sources emit pollutants from one or more controllable sites.

– Fugitive sources generate air pollutants from open areas exposed to wind

processes.

– Area sources are well defined areas within which are several sources of air

pollutants.

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Point source

Fugitive source

Natural Gas Burning off – fugitive source

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Mobile Source of Air Pollution

• Mobile source of air pollutants move from

place to place while emitting pollutants.

– Automobiles, trucks, buses, aircraft, ships, and trains.

About 30 cruise ships carrying a total of nearly one million people visit Alaska over a

five month period. This result is over one billion gallons of cruise discharges being

dumped into unknown areas of Alaska state waters every year.

General Effects of Air Pollution

• Affects many aspects of our environment

– Visual qualities

– Vegetation

– Animals

– Soil

– Water quality

– Natural and artificial structures

– Human health

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General Effects of Air Pollution

• Affect human health in several ways

– Toxic poisoning, cancer, birth defects, eye irritation,

and irritation of respiratory system.

– Increased susceptibility to viral infections, causing

pneumonia and bronchitis.

– Increased susceptibility to heart disease.

– Aggravation of chronic diseases, such as asthma and

emphysema.

• Many air pollutants have synergistic effects

– Do greater damage to the lungs than a combination of

the two pollutants would be expected to do based on

their separate effects.

Air Pollutants

• 200 air pollutants recognized and assessed by US

EP and listed in Clean Water Act

– Six called critical (criteria) pollutants

Impacts of Criteria Pollutants

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Impacts of Criteria Pollutants

Primary and Secondary Pollutants

• Major air pollutants occur either in gaseous forms

or as particulate matter.

• Classified as primary or secondary

– Primary pollutants- emitted directly into the air

– Secondary pollutants- produced through reactions

between primary pollutants and normal atmospheric

compounds.

Sulfur Dioxide

• SO2

– Colorless odorless gas

– Once emitted can be converted to sulfate - SO4

– Removed from atmosphere by wet or dry deposition

– Major human sources; coal power plants, industrial

processes

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Sulfur Dioxide

• Adverse effects depend on dose and

concentration present

– Injury or death to animals and plants

– Corrosion of paint and metals

– Important precursor to acid rain

Nitrogen Oxides

• Occur in many forms in the atmosphere but largely emitted in two forms:

– Nitric oxide- NO

– Nitrogen dioxide- NO2

• A yellow-brown to reddish-brown gas

• May be converted to NO32-

– Both subject to emissions regulation and contribute to smog

– NO2 major contributor to acid rain

Nitrogen Oxides • Nearly all NO2 emitted

from human sources

– Automobiles and power plants

that burn fossil fuels

• Environmental effects

– Irritate eyes and mucous

membranes

– Suppress plant growth

• However when convert to nitrate

may promote plant growth

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Carbon Monoxide • CO is a colorless, odorless gas

– Even at low concentrations is extremely toxic to

humans

• Binds to hemoglobin in blood.

– 90% of CO in atmosphere comes from natural sources

– 10% comes from fires, cars, and incomplete burning of

organic compounds

Ozone and Other Photochemical Oxidants

• Photochemical oxidants result from atmospheric

interactions of nitrogen dioxide and sunlight.

• Most common is

ozone- O3

• Colorless gas w/

slightly sweet odor

• Very active chemically,

oxidizes or burns • Beneficial in the upper

atmosphere

Ozone and Other Photochemical Oxidants

• Because ozone is a secondary pollutant it

is difficult to regulate.

– Health standards often exceeded in urban areas

• Effects include

– Kills leaf tissue at high concentration

– Damage eyes and respiratory system

– Even young, healthy people may have

breathing difficulty on polluted days

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Particulate Matter • PM10 is made up of particles less than 10μm in

diameter

– Present everywhere but high concentrations and/or specific

types dangerous

– Much particulate matter easily visible as smoke, soot, or dust

– Includes airborne asbestos and heavy metals

Particulate Matter

• Of particular concern are very fine pollutants

– PM 2.5- less than 2.5 μm in diameter

– Easily inhaled into the lungs, then absorbed into the

bloodstream

– Ultrafine particles- <0.18 μm released by automobiles.

• Related to heart disease

• When measured often referred to as total

suspended particles (TSPs)

– Tend to be highest in large cities in developing

countries

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Air Quality Standards in Major World

Cities

Particulate Matter

• Recent studies estimate that 2 to 9% of human mortality in cites is associated w/ PM

– Linked to both lung cancer and bronchitis

– Especially hazardous to elderly and those w/ asthma

• Dust can be deposited on plants

– Interferes w/ absorption of CO2 and O2 and transpiration

• Block sunlight and may cause climate change.

• Global dimming

– Gradual reduction in the solar energy that reaches the

surface of Earth

– Cools the atmosphere

– Lessens global warming

Lead

• Lead is constituent of auto batteries and used to

be added to gasoline.

– Lead in gas emitted into air w/ exhaust

– Spread widely around world in soils and water along

roadways

– Once in soil can enter the food chain

– Lead now removed from gas in US, CAN, EU

• 98% reduction in emissions since 1970s

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Air Toxics

• Pollutants that are known or suspected to cause cancer or other serious health problems.

– Associated w/ long-term and short-term exposures

– Gases, metals, and organic chemicals that are emitted in relatively small volumes

– Cause respiratory, neurological, reproductive, or immune diseases

Mobile source air toxics

Air Toxics • Standards have been set for more than 150 air toxics

– E.g. hydrogen sulfide, hydrogen fluoride, chlorine gases,

benzene, methanol, ammonia

– EPA estimates that the average risk for cancer from exposure to

air toxics is about 1 in 21,000

Variability of Air Pollution

• Problems vary in different regions of the country and the world.

– LA pollution mainly from mobile sources

– Ohio and Great Lakes point sources

• Also varies w/ time of year

– Smog a problem in summer when there is lots of sunshine

– Particulates a problem in dry months

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Las Vegas: Particulates

• Particulates a problem in arid regions

– Where little vegetation is present and wind can easily pick up

and transport fine dust.

– Brown haze over Las Vegas partly due to naturally occurring

PM 10

– 60% of the dust comes from new construction sites, dirt roads,

and vacant land.

Haze From Afar

• Air quality concerns are not restricted to urban areas.

– North slope of AK has an air pollution problem that originates

from sources in EE and Eurasia.

– Transported by the jet stream.

– Significant as we try to understand global air pollution.

It works both ways…

Path of a polluted airmass advected from North America to Europe (gray arrow)

and the proposed flight tracks for the NOAA, British and German aircraft.

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Urban Air Pollution

• Whether air pollution develops depends on

topography and meteorological conditions

– Determine the rate at which pollutants are transported

away and converted to harmless compounds.

• In the lower atmosphere, restricted circulation

associated w/ inversion layers may lead to

pollution events.

• Atmospheric inversion-

– Occurs when warmer air is found above cooler air

Influences of Meteorology and Topography

• Meteorological conditions determine whether air

pollution is a nuisance or major health problem.

• Primary adverse effect

– Damage to green plants and aggravation of chronic disease

– Usually low-level over long period of time

– However major disaster have occurred

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Influences of Meteorology and Topography

• Cities situated in a valley or topographic bowl are

more susceptible to smog problems than cities in

open plains.

• Surrounding mountains and inversions prevent

pollutants from being transported by wind or

weather systems.

– E.g. Los Angeles

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Potential for Urban Air Pollution

• Determined by the following factors:

1. The rate of emission of pollutants per unit area.

2. The downwind distance that a mass of air moves through an urban area.

3. The average speed of the wind.

4. The elevation to which potential pollutants can be thoroughly mixed by naturally moving air in the lower atmosphere.

Smog

• Term first used in 1905 as mixture of smoke and fog

that produced unhealthy air.

• Two major types

– Photochemical smog (LA type smog or brown air)

– Sulfurous smog (London type smog, gray air, or industrial

smog)

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Future Trends for Urban Areas

• The optimistic view

– Air quality will continue to improve

– Because we know so much about the sources of air pollution and have developed effective ways to reduce it.

• The pessimistic view

– In spite of this knowledge, population pressures and economics will dictate what happens in many parts of the world,

– The result will be poorer air quality in many locations.

Future Trends for Urban Areas; The United States

• LA is a good area to look at for strategies for pollution abatement.

• Air quality plan involving the entire urban region includes the following features:

– Strategies to discourage automobile use and reduce the number of cars.

– Stricter emission controls for automobiles.

– A requirement for a certain number of zero-pollutant automobiles (electric cars) and hybrid cars with fuel cell and gasoline engines.

Zero Pollution Motors

Future Trends for Urban Areas; The United States

– A requirement for more gasoline to be reformulated to burn

cleaner.

– Improvements in public transportation and incentives for people

to use it.

– Mandatory carpooling.

– Increased controls on industrial and household activities known

to contribute to air pollution.

Carpool Kenny

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Future Trends for Urban Areas; Developing

Countries • Less developed countries w/ growing populations are

susceptible to air pollution

– Don’t have the financial base necessary to fight air pollution

• E.g. Mexico City

– 25 million people

– 50,000 buses, millions of cars, LPG leaks

– In a natural basin w/ mountains surrounding it

– Perfect situation for severe air pollution problem

Pollution Control

• The most reasonable strategies for control have been

to reduce, collect, capture, or retain the pollutants

before they enter the atmosphere.

– Reduction of emissions through energy efficiency and

conservation measures is preferred.

Pollution Control: Automobiles • Control of pollutants such as carbon monoxide, nitrogen

oxides, and hydrocarbons is best achieved through

pollution control for automobiles.

– Nitrogen oxides controlled by recirculating exhaust gas

– CO and hydrocarbons reduced by catalytic converter

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Pollution Control: Automobiles

• Automobile emission regulations plan in US has

not been effective

– Pollutants may be low when car is new

– But many people do not maintain them properly

– Suggested that effluent fees replace emission controls

– Other strategies reduce the number or type of cars (i.e.

the air car or full-on electric vehicles)

Pollution Control: Sulfur Dioxide

• Can be reduced through abatement measures

performed before, during, or after combustion.

• Cleaner coal technology available but makes fuel

more expensive.

• Switch to low-sulfur coal

– But transportation is an issue

Pollution Control: Sulfur Dioxide

• Washing it to remove sulfur

– Iron sulfide settles out

– Ineffective for removing organic sulfur

• Coal gasification

– Converts coal to gas in order to remove sulfur

– Gas obtained is clean

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Pollution Control: Sulfur Dioxide

• Emissions from power plants can be reduced by removing the oxides from the gases in the stack

– Scrubbing (flue gas desulfurization)

– Occurs after coal is burned

– Gases treated w/ a slurry of lime or limestone

– Reacts to form calcium sulfite

– Can then be process into building materials

Clean Air Act Amendments of 1990

• Comprehensive regulations enacted by the U.S. Congress that address acid rain, toxic emissions, ozone depletion, and automobile exhaust.

• Buying and selling of sulfur dioxide emissions

• One step back occurred in 2003 when the president and EPA allowed companies to upgrade w/o new pollution controls.

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Clean Air Act Amendments of 1990

• Also calls for control of

• Nitrogen dioxides

– Reduced by 10 million tons

• Toxins

– Especially those causing cancer

• Ozone depletion in the stratosphere

– End production of all CFCs

Ambient Air Quality Standards

• Important because they are tied to emission

standards that attempt to control air pollution.

• Tougher standards set for ozone and PM 2.5

– When challenged in court justices help that the

EPA’s responsibility is to consider benefits to health

not financial costs.

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Air Quality Index

• AQI is used to describe air pollution on a given day.

• AQI is determined from measurements of the

concentration of five major pollutants:

– Particulate matter, sulfur dioxide, carbon monoxide, ozone, and

nitrogen dioxide.

Air Quality Index

• An AQI value of greater than 100 is unhealthy.

• Air pollution alert is issued if the AQI exceeds 200.

• Air pollution warning is issued if the AQI exceeds 300,

hazardous to all people.

• If the AQI exceeds 400, an air pollution emergency is

declared, and people are requested to remain indoors

and minimize physical exertion.

Irmo AQI

Cost of Air Pollution Control

• Economic analysis of air pollution includes many variables, some of which are hard to quantify. We do know the following:

– W/ increasing air pollution controls, the capital cost for technology to control air pollution increases.

– As the controls for air pollution increase, the loss from pollution damages decreases.

– The total cost of air pollution is the cost of pollution control plus the environmental damages of the pollution.