Chapter 13: Air Chapter 13: Air PollutionPollution

Dr. R. B. SchultzDr. R. B. Schultz

Geography 101: Weather and Geography 101: Weather and ClimateClimate

Air Pollution and WeatherAir Pollution and Weather Air pollution and weather are linked in two ways. One Air pollution and weather are linked in two ways. One

way concerns the influence that weather conditions way concerns the influence that weather conditions have on the have on the dilutiondilution and and dispersaldispersal of air pollutants. of air pollutants.

The second way is the reverse and deals with the The second way is the reverse and deals with the effect that air pollution has on weather and climate. effect that air pollution has on weather and climate.

Air is never perfectly clean. Air is never perfectly clean. Examples of “natural” air pollution include:Examples of “natural” air pollution include:

Ash, Ash, salt particles, salt particles, pollen and spores, pollen and spores, smoke and smoke and windblown dust windblown dust

Air Pollutant TypesAir Pollutant Types Although some types of air pollution are recent Although some types of air pollution are recent

creations, others, such as London's infamous smoke creations, others, such as London's infamous smoke pollution, have been around for centuries. One of the pollution, have been around for centuries. One of the most tragic air pollution episodes ever occurred in most tragic air pollution episodes ever occurred in London in December 1952 when more than four- London in December 1952 when more than four- thousand people died. thousand people died.

Air pollutantsAir pollutants are airborne particles and gasses that are airborne particles and gasses that occur in concentrations that endanger the heath and occur in concentrations that endanger the heath and well-being of organisms or disrupt the orderly well-being of organisms or disrupt the orderly functioning of the environment. functioning of the environment.

Pollutants can be grouped into two categories: Pollutants can be grouped into two categories: (1) (1) primary pollutantsprimary pollutants, which are emitted directly from , which are emitted directly from

identifiable sources, and identifiable sources, and (2) (2) secondary pollutantssecondary pollutants, which are produced in the , which are produced in the

atmosphere when certain chemical reactions take place atmosphere when certain chemical reactions take place among primary pollutants. among primary pollutants.

Primary PollutantsPrimary Pollutants

The major primary pollutants include:The major primary pollutants include: particulate matter (PM),particulate matter (PM), sulfur dioxide, sulfur dioxide, nitrogen oxides, nitrogen oxides, volatile organic compounds (VOCs), volatile organic compounds (VOCs), carbon monoxide, and carbon monoxide, and lead. lead.

Secondary PollutantsSecondary Pollutants Atmospheric sulfuric acid is one example of a Atmospheric sulfuric acid is one example of a

secondary pollutant. secondary pollutant. Air pollution in urban and industrial areas is often Air pollution in urban and industrial areas is often

called called smogsmog. . Photochemical smogPhotochemical smog, a noxious mixture of gases , a noxious mixture of gases

and particles, is produced when strong sunlight and particles, is produced when strong sunlight triggers triggers photochemical reactionsphotochemical reactions in the atmosphere. in the atmosphere.

The major component of photochemical smog is The major component of photochemical smog is ozoneozone. .

Although considerable progress has been made in Although considerable progress has been made in controlling air pollution, the quality of the air we controlling air pollution, the quality of the air we breathe remains a serious public health problem. breathe remains a serious public health problem.

Controlling Air Pollution Controlling Air Pollution through Regulationsthrough Regulations

Economic activity, population growth, meteorological Economic activity, population growth, meteorological conditions, and regulatory efforts to control conditions, and regulatory efforts to control emissions, all influence the trends in air pollution. emissions, all influence the trends in air pollution.

The The Clean Air Act of 1970Clean Air Act of 1970 mandated the setting of mandated the setting of standards for four of the primary pollutants—standards for four of the primary pollutants— particulates, particulates, sulfur dioxide, sulfur dioxide, carbon monoxide, and carbon monoxide, and NitrogenNitrogen as well as the secondary pollutant ozone. as well as the secondary pollutant ozone.

Have Regulations Helped?Have Regulations Helped?

In 1997, the emissions of the five major In 1997, the emissions of the five major primary pollutants in the United States were primary pollutants in the United States were about 31 percent about 31 percent lowerlower than 1970. than 1970.

In 1990, Congress passed the In 1990, Congress passed the Clean Air Act Clean Air Act AmendmentsAmendments, which further tightened , which further tightened controls on air quality. controls on air quality.

Regulations and standards regarding the Regulations and standards regarding the provisions of the Clean Air Act Amendments provisions of the Clean Air Act Amendments of 1990 are periodically established and of 1990 are periodically established and revised. revised.

Air Pollution OccurrencesAir Pollution Occurrences The most obvious factor influencing air pollution is the The most obvious factor influencing air pollution is the

quantity of contaminants emitted into the quantity of contaminants emitted into the atmosphere. atmosphere.

However, when air pollution episodes take place, However, when air pollution episodes take place, they are not generally the result of a drastic increase they are not generally the result of a drastic increase in the output of pollutants; instead, they occur in the output of pollutants; instead, they occur because of changes in certain atmospheric because of changes in certain atmospheric conditions. conditions.

Two of the most important atmospheric conditions Two of the most important atmospheric conditions affecting the dispersion of pollutants are:affecting the dispersion of pollutants are: (1) the strength of the wind and (1) the strength of the wind and (2) the stability of the air. (2) the stability of the air.

Air MixingAir Mixing

The direct effect of wind speed is to influence the The direct effect of wind speed is to influence the concentration of pollutants. concentration of pollutants.

Atmospheric stability determines the extent to which Atmospheric stability determines the extent to which vertical motions will mix the pollution with cleaner air vertical motions will mix the pollution with cleaner air above the surface layers. above the surface layers.

The vertical distance between Earth's surface and the The vertical distance between Earth's surface and the height to which convectional movements extend is height to which convectional movements extend is called the called the mixing depthmixing depth. .

Generally, the greater the mixing depth, the better the Generally, the greater the mixing depth, the better the air quality. air quality.

InversionsInversions Temperature inversionsTemperature inversions represent a situation in represent a situation in

which the atmosphere is very stable and the mixing which the atmosphere is very stable and the mixing depth is significantly restricted. depth is significantly restricted.

When an inversion exists and winds are light, When an inversion exists and winds are light, diffusion is inhibited and high pollution concentrations diffusion is inhibited and high pollution concentrations are to be expected in areas where pollution sources are to be expected in areas where pollution sources exist. exist.

Surface temperature inversionsSurface temperature inversions form because the form because the ground is a more effective radiator than the air above. ground is a more effective radiator than the air above. Inversions aloftInversions aloft are associated with sinking air that are associated with sinking air that characterizes centers of high air pressure characterizes centers of high air pressure (anticyclones). (anticyclones).

Inversion

This is an example of a generalized temperature profile for a surface inversion.

Temperature-profile changes in bottom diagram after the sun has heated the surface.

An Inversion Aloft

Acid PrecipitationAcid Precipitation

In most areas within several hundred In most areas within several hundred kilometers of large centers of human activity, kilometers of large centers of human activity, the pH value is much the pH value is much lowerlower than the usual than the usual value found in unpopulated areas. value found in unpopulated areas.

This acidic rain or snow, formed when sulfur This acidic rain or snow, formed when sulfur and nitrogen oxides produced as by-products and nitrogen oxides produced as by-products of combustion and industrial activity are of combustion and industrial activity are converted into acids during complex converted into acids during complex atmospheric reactions, is called atmospheric reactions, is called acid acid precipitationprecipitation..

Acid Precipitation (cont.)Acid Precipitation (cont.) The atmosphere is both the avenue by which offending The atmosphere is both the avenue by which offending

compounds travel from sources to the sites where they compounds travel from sources to the sites where they are deposited and the medium in which the combustion are deposited and the medium in which the combustion products are transformed into acidic substances. products are transformed into acidic substances.

Beyond possible impacts on health, the damaging Beyond possible impacts on health, the damaging effects of acid precipitation on the environment include effects of acid precipitation on the environment include the lowering of pH in thousands of lakes in the lowering of pH in thousands of lakes in Scandinavia and eastern North America. Scandinavia and eastern North America.

Besides producing water that is toxic to fish, acid Besides producing water that is toxic to fish, acid precipitation has also detrimentally altered complex precipitation has also detrimentally altered complex ecosystems by many interactions at many levels of ecosystems by many interactions at many levels of organization.organization.

Key TerminologyKey Terminology

““Natural” air pollutionNatural” air pollution Primary Primary pollutantspollutants

Secondary pollutantsSecondary pollutants SmogSmog

Photochemical smogPhotochemical smog Photochemical Photochemical reactionsreactions

OzoneOzone Clean Air Act Clean Air Act (1970)(1970)

Mixing depthMixing depth InversionInversion

Surface inversionSurface inversion Inversion aloftInversion aloft

Acid PrecipitationAcid Precipitation

Pertinent Web SitesPertinent Web Sites

Acid RainAcid Rain FAQs FAQs (Environment Canada)) (Environment Canada)) Answers to frequently asked questions about acid rain.Answers to frequently asked questions about acid rain.

Air Pollution - U.S. EPA Office of Air and RadiationAir Pollution - U.S. EPA Office of Air and Radiation

EPA's Office of Air and Radiation (OAR) deals with issues that affect the quality of our air and EPA's Office of Air and Radiation (OAR) deals with issues that affect the quality of our air and protection from exposure to harmful radiation. OAR develops national programs, technical protection from exposure to harmful radiation. OAR develops national programs, technical policies, and regulations for controlling air pollution and radiation exposure. Areas of concern policies, and regulations for controlling air pollution and radiation exposure. Areas of concern to OAR include: indoor and outdoor air quality, stationary and mobile sources of air pollution, to OAR include: indoor and outdoor air quality, stationary and mobile sources of air pollution, radon, acid rain, stratospheric ozone depletion, radiation protection, and pollution prevention.radon, acid rain, stratospheric ozone depletion, radiation protection, and pollution prevention.

Atmospheric Ozone ConcentrationsAtmospheric Ozone Concentrations Ozone concentration maps from the World Meteorological Organization (WMO).Ozone concentration maps from the World Meteorological Organization (WMO).

Atmospheric Pollution (EPA)Atmospheric Pollution (EPA) Here is the Environmental Protection Agency (EPA) atmospheric pollution home page.Here is the Environmental Protection Agency (EPA) atmospheric pollution home page.

Atmospheric Research & Information Centre (ARIC)Atmospheric Research & Information Centre (ARIC) The ARIC is a multidisciplinary centre of excellence for the study and resolution of atmospheric The ARIC is a multidisciplinary centre of excellence for the study and resolution of atmospheric

pollution issues located at Manchester University in England.pollution issues located at Manchester University in England.

Carbon Dioxide Information Analysis Center (CDIAC)Carbon Dioxide Information Analysis Center (CDIAC)

The Carbon Dioxide Information Analysis Center (CDIAC) is the primary global-change The Carbon Dioxide Information Analysis Center (CDIAC) is the primary global-change data and information analysis center of the U.S. Department of Energy (DOE).data and information analysis center of the U.S. Department of Energy (DOE).

Environmental Protection Agency (EPA)Environmental Protection Agency (EPA)

Here is the Environmental Protection Agency's (EPA) home Page.Here is the Environmental Protection Agency's (EPA) home Page.

EPA Internet Site Search EngineEPA Internet Site Search Engine

The Environmental Protection Agency's (EPA) search page can be used to search the The Environmental Protection Agency's (EPA) search page can be used to search the extensive EPA data base.extensive EPA data base.

EPA Topics, BrowseEPA Topics, Browse

Here is a site with access to a wide variety of topics related to the environment hosted by Here is a site with access to a wide variety of topics related to the environment hosted by the Environmental Protection Agency (EPA).the Environmental Protection Agency (EPA).

Montreal Protocol (AFEAS)Montreal Protocol (AFEAS)

An international agreement, known as the An international agreement, known as the Montreal Protocol on Substances that Deplete Montreal Protocol on Substances that Deplete the Ozone Layer,the Ozone Layer, controls the production and consumption of substances that can controls the production and consumption of substances that can cause ozone depletion.cause ozone depletion.

National Air Quality Trends Brochure (1996) - Six Principal PollutantsNational Air Quality Trends Brochure (1996) - Six Principal Pollutants

This site has an in-depth report on the six principal atmospheric pollutants.This site has an in-depth report on the six principal atmospheric pollutants.

Ozone DepletionOzone Depletion

This site contains information about ozone depletion from the Environmental Protection This site contains information about ozone depletion from the Environmental Protection Agency (EPA).Agency (EPA).