Chemistry in the Environment: Atmosphere

Earth’s atmosphere as seen from spacePhoto: NASA

What are the natural components of our atmosphere?

78 % Nitrogen

21 % Oxygen 1 % Argon

and other trace gases

Composition of the Atmosphere

Troposphere◦ Most of our weather

occurs in this layer closest to the Earth’s surface

Stratosphere◦ Where ozone (O3)

absorbs harmful UV radiation from the Sun and prevents it from reaching Earth’s surface

Layers of the Atmosphere

Atmosphere contains the air we breathe Protects us from the Sun’s radiation Keeps Earth balanced traps and releases

heat

Atmospheres of other planets are different◦ Mars very thin atmosphere made of mostly CO2◦ Venus denser and hotter than Earth’s

atmosphere◦ Jupiter large, turbulent atmosphere made of H

and He

Why do we need an atmosphere?

What are ways that human activity has negatively

affected the atmosphere?

Fossil fuels are fuels formed by natural resources such as anaerobic decomposition of buried dead organisms.

Fossil fuels are non-renewable resources because they take millions of years to form, and reserves are being depleted much faster than new ones are being made.

Fossil Fuels

We burn fossil fuels to produce useful energy

This fuel provides gas for our cars, electricity for our homes, and runs factories and powerplants

Why do we burn fossil fuels?

The burning of fossil fuels produces around 21.3 billion tons (21.3 gigatons) of carbon dioxide (CO2) per year

Burning of Fossil Fuels

What are ways that human activity has contributed to the pollution that causes

smog and acid rain?

A type of air pollution that comes from internal combustion engines and industrial fumes that react with sunlight to form photochemical smog

The word ‘smog’ comes from a combination of smoke and fog

Mixture of air pollutants, including gases and particles that are too small to see

Smog is also caused by large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide

What is smog?

Type: Particulate Matter - or PM. This is the name given to microscopic particles that pollute the air. They vary in size and chemical make-up.Sources: Industrial and vehicle emissions, road dust, agriculture, construction and wood burning.

Type: Ground-level Ozone. This gas is the result of a chemical reaction when certain pollutants are combined in the presence of sunlight. Ground-level ozone shouldn't be confused with the ozone layer in the sky, which protects us from ultraviolet radiation.Sources: Ground-level ozone comes mostly from burning fossil fuels for transportation and industry. Ozone levels peak between noon and 6 p.m. during the summer months.

What types of air pollution cause smog?

Type: Sulfur dioxideSources: Coal-fired power plants and non-iron ore smelters

Type: Carbon monoxideSources: Mostly from burning carbon fuels (e.g. motor vehicle exhaust)

Air Pollution Continued…

Smog in Major US Cities

Smog in Major International Cities

Acid rain is a rain or any other form of precipitation that is unusually acidic (has a low pH)

Acid rain is caused by emissions of sulfur dioxide and nitrogen oxides which react with the water molecules in the atmosphere to produce acids

Acid Rain

What are some effects of smog and acid rain on the

environment?

Asthma Lung Cancer

Can cause coughing, chest pains, throat irritation

Colds and pneumonia

Side Effects of Exposure to Smog

Can damage buildings and historic monuments, especially those made of rocks such as limestone and marble containing large amounts of calcium carbonate

Soil biology and chemistry can be damaged because microbes cannot tolerate changes in pH

As lakes and river become more acidic, biodiversity is reduced◦ Because of low pH, fish eggs may not hatch and some

adult fish are killed◦ Eliminates insect life and some fish species (brook

trout)

Adverse Effects of Acid Rain

Effect of acid rain on a forest in Jizera Mountains, Czech Republic

What has been done or is being done to reduce the

pollution that causes smog and acid rain?

Founded in 1990 by US Environmental Protection Agency (EPA)

Goal is to reduce overall atmospheric levels of sulfur dioxide and nitrogen oxides, which cause acid rain.

The program is an implementation of emissions trading that targets coal-burning plants, allowing them to buy and sell emission permits.

Acid Rain Program

There are several options for reducing SO2 emissions, including using coal containing less sulfur, washing the coal, and using devices called “scrubbers” to chemically remove the SO2 from the gases leaving the smokestack

Powerplants can use different fuels burn natural gas instead of coal

Clean up smoke stacks and exhaust pipes

Nuclear power Hydropower Wind energy Geothermal energy Solar energy

Use alternate energy sources

Takes many years for ecosystems to recover from acid rain even after emissions are reduced and rain pH is back to normal

“Liming” = a process in which limestone or lime is added to acidic lakes to cancel out the acidity ◦ Disadvantage: expensive and short-term solution

Restore a damaged environment

Reducing and controlling the emissions from powerplants and cars

Implement cost-effective mechanisms to reduce emissions

Look to the future

Turn off lights, computers, and other appliances when you're not using them.

Use energy-efficient appliances: lighting, air conditioners, heaters, refrigerators, washing machines, etc. For more information, see EPA’s ENERGY STAR Program.

Only use electric appliances when you need them. Keep your thermostat at 68°F in the winter and 72°F in the

summer. You can turn it even lower in the winter and higher in the summer when you are away from home.

Insulate your home as best you can. Carpool, use public transportation, or better yet, walk or bicycle

whenever possible Buy vehicles with low NOx emissions, and properly maintain your

vehicle. Be well informed.

Take action as individuals

What are ways that human activity has

affected the balance of greenhouse gases in the

atmosphere?

Gases which absorb and emit radiation Greenhouse Gases (GHG):

◦ Water Vapor◦ Carbon Dioxide◦ Methane◦ Nitrous Oxide ◦ Ozone◦ Chlorofluorocarbons (CFCs)

Greenhouse Gases

The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions

The greenhouse effect keeps our planet warm

If we had no atmosphere, our Earth would be 32°C colder than it is today

Greenhouse Effect

Greenhouse Effect

Global anthropogenic greenhouse gas emissions for the year 2000

Household activities which produce Greenhouse Gases

What are some effects of increased greenhouse gas

concentrations on the environment?

Increasing CO2 Concentrations

Plants need CO2 to survive, and plants exposed to more CO2 could grow up to 50% faster than normal

Increased global temperature due to greenhouse effect

What does increased CO2 concentrations mean for the Earth?

Average Global Temperatures

What has been done or is being done to reduce the

concentration of greenhouse gases in the

atmosphere?

What’s wrong with this picture?

What are ways that human activity has contributed to the

reduction of the ozone layer?

What are some effects of the reduced ozone layer on

the environment?

What has been done or is being done to repair the

ozone layer?

Treaty signed in which banned the use of CFCs and HFCs

Montreal Protocol