The Atmosphere

B2: Air Quality

Air Quality• Air Quality – the degree to which the

ambient air is pollutant-free.–Pollutant – substance in the air, water, or

soil that is harmful to living things

–Air Quality Index (AQI) – a number used by government agencies to indicate the degree to which the air is polluted – As the level of pollution increases, the

number increases.

–Different countries have their own AQI scale which are currently not consistent

Air Quality• United States – The Environmental Protection

Agency (EPA) has developed their own AQI.

–Divided into six categories of increasing health concern

– The U.S. AQI is based on the 5 pollutants regulated by the Clean Air Act

–Ground level ozone,particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide

AQI Report for July 29th

Air Quality–Most weather websites will report the AQI –Weather

Channel Report

Sources of Pollution• Sources – Pollution can occur naturally and

as a result of human activities–Natural Sources – many natural

processes add particles to the atmosphere

– Forest fires, soil erosion, and dust storms release a great deal of particles into the air

– The wind carries particles of mold and pollen

– Volcanoes erupt with great clouds of ash and poisonous gases

Sources of Pollution–Human Sources – Activities human engage in

that increases pollutants– Farming and Construction – Can send soil

and dust into the air– Fossil fuels – The majority of air pollution by

humans is the result of burning fossil fuels – Fossil fuels are burned in cars, homes,

factories, and power plants– Produces soot (particles and

hydrocarbons), carbon monoxide, nitrogen oxide, and sulfur dioxide

– Causes smog and acid rain

Smog and Acid Rain• Smog – Combination of the words ‘smoke’ and ‘fog’

– Soot Smog – Forms when particles in coal smoke combine with water droplets in humid air

– First noted 100 years ago in London, England where factories and most homes were heated with coal

– Air became filled with soot which combined with the fog to create a dark, dirty cloud that hung over the city

– Today, they burn much less coal which has resulted in cleaner air

Smog and Acid Rain–Photochemical Smog – Formed by the

action of sunlight on pollutants such as hydrocarbons and nitrogen oxides– These chemicals react to form a brownish

mixture of ozone and other pollutants

– This type of fog is typically found in large cities with lots of sun

–However wind can disperse these pollutants for many miles around

Smog and Acid Rain• Acid Rain – Rain that is more acidic than

normal rain (which is naturally slightly acidic)– Formation – Burning coal, which contains

sulfur, produces sulfur oxide – Sulfur oxides combine with nitrogen

oxides and the water in the air– The combination of the three forms nitric

acid and sulfuric acid– Then rain, sleet, snow, and fog carry

these two acids into trees and lakes

Smog and Acid Rain– Effects – Acid rain causes a lot of environmental

damage that can affect entire ecosystems

– Can make water so acidic that plants, amphibians, and fish can no longer survive in it.

– Kills trees and forests, especially needle-leaf trees like pine and spruce

– It can also damage the surfaces of buildings and statues

Effect of PollutionPollutant Source Health Effect

Carbon Monoxide

Nitrogen Dioxide

Burning of fossil fuels

Reduced ability of blood to deliver oxygen to cells

Burning of fossil fuels

Breathing problems, lung damage

OzoneChemical reaction of certain carbon

compounds

Breathing problems, asthma, eye irritation

Particles (dust,

smoke, soot)

Burning of wood, fossil fuels, and

volcanic eruptions

Respiratory illnesses, nose and throat

irritation and infections

Sulfur Dioxide

Burning of fossil fuels & volcanic

eruptions

Breathing problems, lung damage

Improving Air Quality• Quality – In the U.S., federal and state

governments have passed laws and regulations to reduce air pollution– In general, air quality has improved over

the past 30 years–Newer cars cause less pollution than older ones– Recently-built power plants are less polluting

–However, there are more cars and power plants than ever before

–Many American cities are still polluted

Improving Air Quality– Voluntary measures such as car pooling, using

public transportation, and energy saving appliances, window, and heating all help reduce pollutants

– Some people want more regulations–Others argue it is expensive and should not

be mandated

In Closing–What do you think we should do to reduce air

pollution?