Atmospheric Chemistry

Done by: Soh Zheng Yang

Class: 3B118

Agenda

• Introduction• Composition• Pollutants• Acid Rain• Global Warming• Ways to prevent Global Warming

Introduction

• Many effects on earth, such as global warming , are brought by chemical reactions.

• The Earth is surrounded by a think air layer called the atmosphere. Air is essential for life. Without air, life would not be possible.

Composition

Atmosphere composition…• Nitrogen 78.084%• Oxygen 20.946%• Argon 0.934%• Other gases >1%

Atmospheric chemistry allows us to understand the changes of atmosphere composition and gives us views on the air pollution, thus making us to protect the earth……

Pollutants

Pollutants can come from both natural sources and from human activities. However, human are usually the main cause of the atmospheric problems as 80% of the world-wide energy demand is currently supplied by the fossil fuels coal, oil or gas.

6 main pollutants: Natural Sources:• Sulfur dioxide - Volcanic eruptions• Nitrogen oxides - Forest fires • Carbon monoxide - Biological processes • Methane• Unburnt hydrocarbons• Ozone

Sulfur Dioxide

• Petroleum and Coal are used as fuels to generate energy. • However, large amount fossil fuels are burnt in industries to

provide energy. • Both these fuels contain sulfur as an impurity.

When these fuels are burnt, the sulfur is oxidized to form sulfur dioxide.

S(s) + O2(g) SO2 (g)

(present (present

in fuel) in air)

Nitrogen Oxides

• At high temperatures, nitrogen and oxygen in the air combine to form nitrogen monoxide.

• The nitrogen monoxide combines with more oxygen molecules in the atmosphere to become nitrogen dioxide.

• Occurs Naturally in lighting and forest fires• Most produced inside vehicle engines and Incinerators.

N2 (g) + O2 (g) 2NO (g)

2NO (g) + O2 (g) 2NO2 (g)

Carbon Monoxide

• Carbon Monoxide is a colorless, odorless, and tasteless gas.• Mostly comes from incomplete combustion of fuel in engines.• Highly toxic to humans and animals in higher quantities.• It combines with hemoglobin in the red blood cells to produce

carboxyhemoglobin in normal persons.• It is especially dangerous because it is colourless and

odourless, without any warning of its presence.

Video on the effects: http://www.youtube.com/watch?v=wKIrbq2pWvw

Methane

• Methane is a colorless, odorless gas.• Naturally present in the atmosphere from the bacterial

decay of vegetation and other sources.(Small amount)• Increasing amount because of human activities.• Methane is a relatively potent greenhouse gas, trapping the

heat in the atmosphere causing Global warming.

Unburnt Hydrocarbons

• Produce when incomplete combustion of octane in petrol.

• hydrocarbons emitted after petroleum is burned in an engine

Ozone

• Form of Oxygen; Colourless gas.• Ozone layer in the upper atmosphere Surrounds the Earth

at high altitudes and prevents us from harmful solar radiation.

However......• An air pollutant at the lower atmosphere with harmful

effects on the respiratory systems of animals and burning sensitive plants.

Next page……

Ozone Hole

• A portion of the layer is depleted by chlorofluorocarbons(CFCs)

• Although CFCs are harmless, they can rise up high into the atmosphere and decomposed by sunlight to produce chlorine atoms.

• The chlorine atoms react with the ozone molecules and destroy them by converting them into oxygen molecules.

Photochemical Smog

• Caused by reactions between sunlight and pollutants.

• Often invisible, it can be extremely harmful, leading to irritations of the respiratory tract and eyes.

Acid Rain

• Formed from 2 air pollutants – sulfur dioxide and nitrogen dioxide.

• Sulfur dioxide and nitrogen dioxide reacts with oxygen and water to form sulfuric acid and nitric acid respectively which dissolves in rainwater, making it acidic.

2SO2 (g) + O2(g) + 2H2O (l) SO2 (g)

Effects of Acid Rain

• Causes soils to become acidic, plants do not grow well.• Cause water to become acidic which results in the many

deaths of marine life.• Corrodes buildings made of limestone or cement as they

react with calcium carbonate.

Global Warming

• Increasing volume of atmospheric Methane and Carbon dioxide.

• Trap the heat radiation and prevent it from entering the space.

• Due to human activities, this greenhouse gases" is occupying more percentage in the total composition of air.

• Resulting the Earth to become hotter.

Consequences of Global Warming

• The polar ice caps will melt.• Seawater will expand and sea levels will rise, causing

frequent flooding of low-lying areas.• Aquatic animals’ habitats will be greatly affected, causing

animals like polar bears to become extinct.

Preventing Global Warming

• Reducing the amount of fossil fuels burned by using solar panels.

• More electricity could be generated through other means such as wind, tidal, hydroelectric power.

• Say “No” to Global Warming

References

• http://www.wisegeek.com/what-is-photochemical-smog.htm• http://www.google.com.sg/imghp?hl=en&tab=ii• http://en.wikipedia.org/wiki/Atmospheric_methane

• The End~