Chp. 20
The Atmosphere
a thin layer of gases surrounding the earth. it has density and atmospheric pressure. they both vary throughout the atmosphere due to gravitational forces that pull the gas molecules towards the Earth’s surface. Atmospheric pressure is measured by mass per unit in air. ATMOSPHERIC PRESSURE DECREASES WITH ALTITUDE. AIR AT SEA LEVEL HAS A HIGHER DENSITY THAN AIR AT THE TOP OF A MOUNTAIN. the ATMOSPHERE is divided into spherical layers with different temperature, pressure, and composition.
Layers of the Earth’s Atmosphere
Closest to most far
1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
The Troposphere
75-80% of earth’s mass
closest to earth’s surface
at equator:extends 11 miles
at poles:extends 5 miles
Nitrogen: 78%
Oxygen: 21%
Water Vapor, CO2, Argon, and other gases: 1%
Long-term climate, short-term weather, and Earth’s geo-chemical cycles
lower 15km of atmosphere
the air is fairly similar due to TURBULENCE AND MIXING
highest gas concentration at 10-50km
Ozone
highest concentration at 100-200km
Nitrogen
Highest concentration at 200-1100km
Oxygen
Highest concentration at 1100-3500
Helium
Above 300km
Hydrogen
The Stratosphere
contains the GOOD ozone;
-keeps away 95% of harmful UV radiation
-protects us from immune damage, cancers, cataracts, and sunburn of the eyes and skin.
it is the second layer of the Earth’s Atmosphere
it extends 11-30 miles above the earth’s surface
Ozone
it is produced when oxygen molecules mix with UV radiation
the GOOD OZONE in the STRATOSPHERE is DECREASING
the BAD OZONE in the TROPOSPHERE is INCREASING 🙁
Air Pollution
high concentrations of chemicals in the atmosphere that affect climate and harm organisms and materials
Primary Pollutants
enter directly into the atmosphere; soot and carbon dioxide
Secondary Pollutants
primary pollutants mixed together
Classes of air pollutants
carbon oxides, sulfur oxides, nitrogen oxides, VOC’S, PTM’s, photochemical oxidants, radioactive substances, and hazardous air pollutants
Air Pollutants come from these natural sources
Forest fires, volcanic eruptions, VOC’s released by plants, dust particles, decay of plants, and sea spray.
Tropospheric Ozone
formed as a result of photochemical reactions between VOC’s and nitrogen oxides. Ozone concentrations are greatest on warm sunny days and are associated with high air pressure
Tropospheric ozone on Human Health
harmed lung disease, impaired body’s defense mechanisms, increased respiratory tract infection
Photochemical smog
poor air quality caused by nitrogen oxides and VOC’s.
Associated with high air pressure and temperature inversions
Pollution management strategies
reduce the use of private vehicles, one-day stop driving events, enforce engine maintenance standards, and change fuels
Tall Chimneys
Output approach to pollution
Tall Smokestacks
reduce LOCAL pollution, cause REGIONAL pollution
Dry Deposition
particles, aerosols, and gases.
Wet Deposition
rain, snow, hail, fog, or mist. pH lower than 5.6
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