THE EARTH’S ATMOSPHERE

The atmosphere is the envelope of gases that surround our planet

It is a very thin layer compared to the radius of the Earth

We refer to this layer informally as “air”

The majority of the energy that drives the atmosphere is from the Sun.

The atmosphere receives most of this energy from the surface.

Atmospheric CompositionDry air (neglecting water vapor) is

composed of the following gases:

Nitrogen (N2) = 78%

Oxygen (O2) = 21%

Argon (Ar) = 1%

Trace Gases

Dust, bacteria, and other particulates

Atmospheric Composition Trace Gases

Gases that are only found by examining a million or billion air molecules

Examples include:○ Carbon Dioxide (CO2) = 340 ppmv

○ Neon (Ne) = 18 ppmv○ Helium (He) = 5 ppmv○ Methane (CH4) = 2 ppmv

○ Hydrogen (H2) = 0.5 ppmv

Atmospheric Molecules

Note that the Oxygen, Nitrogen, and Hydrogen that we breathe are not single atoms of that gas, but instead are two atoms of that gas bonded together in what is called a diatomic molecule.

Ozone is an example of a triatomic molecule with three oxygen atoms.

Atmospheric Composition

Water vapor (H2O) is a variable gas. You will see it depends on temperature and the availability of liquid water. A volume of air can have between 0% and 4% water vapor, and this varies both in time and space.

THE EARLY ATMOSPHERE

Hydrogen and Helium as starting materials

Presence of methane and ammonia

Water vapor, carbon dioxide, nitrogen

OUTGASSING

Formation of oceans and other bodies of water

Formation of early limestone and rocks

Depletion of carbon dioxide and water abundance of nitrogen gas

Abundance of oxygen ?

H2O Oxygen

Hydrogen

LAYERS of the ATMOSPHERE

TROPOSPHERE

Innermost layer

Contains most of the air molecules necessary for life

Starts at the surface of the earth – 17 km vertically

Weather changes

Lowest Part Higher temperature

Higher Part Temperature decreases

Air pressure is lower

Above 11 km Temperature stops decreasing

(tropopause)

Remains constant with height

STRATOSPHERE

About 20 km above Earth’s surface

Extends from about 17 to 48 km

Temperature gradually increases

Ranges from -60C to -50 C

Calm air

Almost same composition as the troposphere but with greater water vapor and ozone

“global sunscreen”

Presence of OZONE molecules Absorbs UV radiation Formation of OZONE

O2 + UV 2O

O + O2 O3

O3 + UV 3O2

OZONE LAYER Region between 20 km and 30 km

The UPPER ATMOSPHERE

MESOSPHERE Above 50 km Air is very thin Very few oxygen molecules Average temperature is -90 C

THERMOSPHERE Outermost layer Very few molecules of air present High temperature ( 2000 C) auroras Ionosphere

EXOSPHERE

Very thin layer which merges into the outer space.

Global Processes

GREENHOUSE EFFECT

OZONE SHIELD

SHORT QUIZ

Why is the OZONE LAYER very important to human life ?

Greenhouse effect and ozone shield are natural processes essential to life that takes place in the atmosphere. What happens to these when we add chemicals to the atmosphere? Be specific.

The Air We Breathe

N2

CO2

Water vapor

Argon

- Unreactive

- Useful application in industry - Inert filler gas for light bulbs- Extends the life of light bulbs

What else could we possibly inhale when we breathe?

CO2

SO2

O2

Pb Other particulate matter

AIR POLLUTION

WHAT is AIR POLLUTION?

Stationary and Area SourceSTATIONARY SOURCE emission source that

does not move

large emitters who release relatively consistent qualities and quantities of pollutants.

Stationary and Area SourceAREA SOURCE smaller stationary

sources located together whose individual emissions may be low but whose collective emissions can be significant

Mobile Sources capable of moving

under its own power; imply on-road transportation

non-road or off-road category (gas-powered lawn tools and mowers, farm and construction equipment, recreational vehicles, boats, planes, and trains)

Agricultural Sources

raise animals and grow crops, can generate emissions of gases, particulate matter, and chemical compounds.

Agricultural Sources For example, animals

confined to a barn or area (rather than field grazing), produce large amounts of manure.

Manure emits various gases, particularly ammonia into the air.

Agricultural Sources In crop production, the

misapplication of fertilizers, herbicides, and pesticides can potentially result in aerial drift of these materials.

Natural Sources not caused by people

or their activities erupting volcano emits

particulate matter and gases

forest and prairie fires can emit large quantities of pollutants

Natural Sources not caused by people

or their activities plants and trees emit

hydrocarbons; and dust storms can create large amounts of particulate matter.

Natural Sources wild animals in their natural

habitat are also considered natural sources of pollution

given that there is a certain amount of natural pollution, it is very important to control the "excess" pollution caused by man’s activities.

Major Pollutants

PRIMARY

Enters the air as the direct result of a specific activity

SECONDARY

Formed by the further reaction of a primary air pollutant

Sulfur dioxide

4 FeS2 + 11O2 - 2Fe2O3 + 8 SO2

forms as coal and petroleum products burn an irritating gas with a harsh acrid odor

pyrite oriron pyrite

oxygen iron oxide sulfurdioxide

Primary or secondary?

Sulfur trioxide

2 SO2 + O2 - 2 SO3

Highly irritating gas Choking, irritating sensations

sulfurdioxide

oxygen sulfurtrioxide

Sulfur trioxide

2 SO3 + H2O - H2SO4

Dissolves in atmospheric water droplets to produce acid rain

sulfurtrioxide

water sulfuricacid

Primary or secondary?SOx

Nitrogen oxides (NOx)

Nitrogen comes from the air rather than from impurities in fuels

High temperature of lightning and combustion chambers of the internal combustion engine

N2 + O2 - 2 NO

nitrogen oxygen nitric oxide

Primary or secondary?

Nitrogen dioxide

Red-brown toxic gas Irritation to the eyes and the respiratory system Inflammation of the lungs, fatal in a few days Produce HNO3, a component of acid rain

2 NO + O2 - 2 NO2

nitric oxide oxygen nitrogendioxide

Primary or secondary?

OUTDOOR Air Pollution

Fuel Combustion

Carbon monoxide Odorless, tasteless,

and invisible

Drowsiness, headache, dizziness, and nausea

Has greater affinity to hemoglobin

Can lead to asphyxiation or even death

Soot

Soft black allotrope of carbon

Contains PAHs

Carbon dioxide Primary product of combustion

A greenhouse gas

Lead (Pb) Burning of leaded gasoline Neurotoxin

Other sources of lead ?

Airborne Pathogens

Disease-causing agents SARS

Particulate Matter

Very small solid or liquid droplets

Soot, pollen, smoke particulates, and dust

PM-10Lead, iron, copper, nickel particulates

Photochemical Smog

NO2 - NO + Onitrogendioxide

nitricoxide

oxygenatom

O + O2 - O3

oxygenatom

oxygenmolecule

ozone

sunlight

Photochemical Smog a still, sunny day

temperature inversion (pollutants accumulate in the lower inversion layer)

Organic compoundsVOC and VOS Volatile hydrocarbon components of consumer

products (paint thinners, roof tar, petroleum distillates)

Evaporating solvents and propellants (nail polish, deodorants, after-shave lotions, hair sprays, insecticides)

Ethyl acetate and more exotic additives that you exhale (chewing gum and breath fresheners)

Acid Deposition

Acid Rain

Acid Rain

Ozone DepletionOZONE

a form of oxygen, contains three oxygen atoms  unstable and will readily combine with other atoms

found in the stratosphere, where it blocks the sun's ultraviolet (UV) waves and prevents them from reaching the earth's surface

also found in the troposphere, where it can damage livingtissue and human-produced objects. It is generated both from certain types of pollution and natural sources

ozone

absorbs the potentially harmful ultraviolet (UV) radiation from the sun

Ozone

Source: World Meteorological Organization, Scientific Assessment of Ozone Depletion: 1998, WMO Global Ozone Research and Monitoring Project - Report No. 44, Geneva, 1998

www.epa.gov/ozone/science/sc_fact.html

Ozone

Ozone Depletion

Chain Initiation

Chain Propagation

ozone

Southern HemisphereSeptember 17, 2001

The “ozone hole” forms over Antarctica during the Southern Hemisphere spring.

In 2001, the ozone hole extended over about 26 million square kilometers, larger than the area of the continental United States!

INDOOR Air Pollution

HW. Notebook

What is indoor pollution?

What are the sources of indoor pollution?

List at least 5 chemical found in your household that can be a source of indoor pollution.

INDOOR Air Pollution

Environmental Tobacco Smoke

ETS Combination of mainstream smoke and

sidestream smoke Contains about 4000 chemical

compoundsAmmonia, hydrogen cyanide, toluene

Nicotine

Common Household chemicals

Insects spray Toilet cleaners Moth repellants Dog sprays Shampoos Air freshener Colognes Perfumes

HW. Notebook Air Pollutant Description Health Risks

Dust Mite

ETS

VOCs

Combustion Product

Chlorinated Chemicals

Asbestos