Atmospheric Chemistry Lecture 5

Study Notes

Atmospheric Composition

99% of the atmosphere is composed of nitrogen and oxygen
1% is made up of trace gases, with argon being the most prevalent
Minute amounts of CO2 and O3 are also present

Importance of the Atmosphere

Acts as a protective blanket for the Earth
Provides CO2 for plants, O2 for respiration, and N2 for nitrogen-fixing bacteria
Stabilizes the Earth's temperature

Layers of the Atmosphere

Troposphere

Extends from 10-18 km above the Earth's surface
Composed of nitrogen and oxygen
All life processes occur in this layer, which is most affected by anthropogenic pollution

Stratosphere

Extends up to 50 km above the Earth's surface
Less dense than the troposphere
Exposed to more radiation, resulting in higher kinetic energy
Contains nitrogen, oxygen, NOx, and ozone

Ozone Layer

Located between 19-48 km above the Earth's surface
Composed of 10 ppm of ozone, which absorbs 97-99% of UV radiation
Can be destroyed by chlorofluorocarbons, bromine halocarbons, and nitrous oxides

Mesosphere

Extends from 50-90 km above the Earth's surface
Composed mostly of ions, similar to the stratosphere
More intense radiation ionizes molecules, making it the coldest layer

Thermosphere

Extends from 90-800 km above the Earth's surface
Composed of a mixture of ions and charged atoms
Uppermost and thickest layer, with high temperatures

Exosphere

Extends from 800-3000 km above the Earth's surface
Outermost layer, with low density and molecules in a collisionless state
Satellites orbit in this layer

Atmospheric Gases

Nitrogen: geochemically inert, accumulated in the atmosphere
Oxygen: cycles through the atmosphere
Argon: noble gas, inert, with most common isotope being argon-40 from radioactive decay of potassium-40
CO2: 340 ppm, with high levels affecting the Earth's climate

Air Pollutants

Classified into primary and secondary pollutants
Primary pollutants: directly emitted from sources, such as mobile sources, stationary sources, area sources, and natural sources
Secondary pollutants: formed from precursor gases that undergo chemical reactions

Types of Air Pollutants

CO: colorless, odorless, and toxic, binding to hemoglobin and interfering with oxygen delivery
NO2: highly reactive, reddish-brown gas, lung irritant, and causes haze and smog
Heavy metals: non-toxic (selenium, copper, zinc) and toxic (cadmium, lead, mercury), with some being carcinogenic (arsenic, chromium, cadmium)
SO2: colorless, non-flammable, and non-explosive, with a pungent odor, causing irritation of eyes, nose, and throat
PM: mixture of small solid particles and liquid droplets, with types including inhalable coarse particle (PM10) and fine particles (PM2.5)

Description

This quiz covers the composition of the atmosphere, including nitrogen, oxygen, and trace gases. It also explores the importance of the atmosphere, including its role in protecting life on Earth and regulating the planet's temperature. Learn about the different layers of the atmosphere, including the troposphere and stratosphere.