the state of the atmosphere at a given time and place depends on: amount of cloudstemperature air pressurewind amount of moisture

A thick blanket of gases surrounding the Earth composed of AIR (a mixture of gases) Makes conditions on Earth suitable for life

Nitrogen (N) 78% Oxygen (O)21% Also, Carbon Dioxide (CO 2 ), H 2 O Vapor, and Argon (Ar) in small amounts

Nitrogen Essential to living things Used to grow & repair cells Cannot obtain N 2 from the air-bacteria fix nitrogen in soil for use

Oxygen Essential to living things & some non living Combustion Oxidation (rusting) Molecule O 2 or O 3

3 oxygen atoms bonded together O is an atom of Oxygen (O) O 2 is atmospheric Oxygen (O-O) O 3 is ozone (O-O-O)

Absorbs 99% of harmful ultraviolet rays from the sun ozone layer is about 10 to 20 km thick thinning is the result of chloroflorocarbons (CFC’s) containing chlorine, fluorine, and carbon

Carbon Dioxide CO 2 Essential to life Plants rely for food Animals-waste product Released during combustion Excess may contribute to global warming

Water Vapor Water as a gas H 2 0 Invisible Amount varies by time & place Forms clouds during condensation

Particles in Air Air in nature is not pure Contains tiny particles of: Dust Smoke Salt

Smog Smoke & fog 1 st used to describe air pollution produced by burning coal during the IR in London

Houston on a smoggy day (left) and a clear day (right).

Pollutants Harmful substances in air, water, or soil Higher concentrations in larger cities Some natural Most by human activity: Burning fossils fuels such as: Coal, Oil, Gas, Diesel –½ from cars & other vehicles –Factories & power plant

Natural Sources Salt Spray Plant pollen Forest fires Soil erosion Dust storms Volcanic eruptions

Human Activity Burning fossil fuels Photochemical smog: photo- meaning “light” caused by sunlight on chemicals –Nitrogen in the warm air reacts w/burning hydrocarbons –Irritates breathing, harms plants, damages rubber, paint, & plastics

Acid Rain Forms when nitrogen oxides & sulfur oxides (produced from burning fossil fuels) combine w/water in the air Can harm trees, pollute ponds & lakes, & kill small organisms (fish, amphibians, insects, & plants)

Improving Air Quality Laws & regulations for filters on: –Cars –Smoke stacks Filters called “scrubbers” More fuel efficient vehicles Public transportation