The Effects of Air Pollution on the Melting of Polar Ice

The Effects of air pollution on the melting of Polar ice

Purpose:

To learn about the effects of air pollution on Sea Ice
Library/computer lab-based activity

Time

Preparation:Reserve the use of the computer lab/library

Class time:One research period, followed by 30 minute discussion time, the following day

Materials

Library, or computer lab – ideally, one computer per person
Two homemade sets of ice cubes – one made with tap water, the other made with salt water
Class set of plastic Petri dishes, or some other containers in which to melt ice cubes, magnifying glass/hand lens

Procedure

Teacher:

Mix up a 3.5% solution of NaCl. Make enough “sea-ice” cubes for each pair of students

Make another class set of ice cubes with tap water. Leave the ice in the freezer until after the research

Students:

Examine the two different kinds of ice cubes, and make a list of any differences.

*Ice cubes made of salt water are more porous and less dense than pure water ice cubes.

Research to answer the following questions:

What airborne pollutants are accumulating in the Arctic?

*Answers may include and are not limited to SO2, NO2, dioxins, sulphates, dust, POP’s, such as DDT and other pesticides, metals such as cadmium and mercury. Many airborne pollutants are carried from industries located elsewhere.

Use your knowledge of chemistry to determine what substances the above pollutants form, when added to water/ice.

*eg. SO2 forms sulphuric acid, NO2 forms nitric acid. Some of the pollutants above, such as dioxins and DDT, travel up the food chain, concentrating at the top of the food chains. Organisms at the top of the food chain may experience problems in reproduction, disease and eventual death.

If pollutants form a haze over ice, what do you think the result will be on glacial melting?

*If haze forms over the ice, the ice will reflect less light energy and absorb more heat energy.

This will result in increased melting.

Describe one Arctic ecosystem as it is now. What effect will the haze have on that ecosystem?

*The following example shows many food chains forming a food web. The chemicals in the haze will precipitate and fall to the snow, ice and oceans. The chemicals bioaccumulate in the fat of organisms, causing multiple problems/death. This of course has an immediate effect on its consumer, and so on up the food chain/web.

Use the prepared ice cubes to see if there is any difference in the rate of melting of one type of ice over the other. Compare your results with those of your classmates.

* Salt water freezes at -2°C, freshwater at 0°C. (Therefore, you may observe the saltwater ice melting more quickly)

*As sea ice forms, visible needles form, trapping the salt water or brine. The salt/brine sinks downward, leaving the top of the ice pure. Therefore, the “pack ice that is formed is pure, and doesn’t contain any salt.

Discussion

What is sea ice and how is it formed?

*Sea ice is ocean water that freezes. As sea ice forms, visible needles form, trapping the salt water or brine. The salt/brine sinks downward, leaving the top of the ice pure. Therefore, the “pack ice that is formed is pure, and doesn’t contain any salt.

What are two types of sea ice?

* Two types of sea ice are

a) Multi-year ice – remains frozen and the top surface of ice that melts, drains to the bottom, remaining under the floating ice. In the winter, this meltwater re-freezes at the bottom of the ice.

b) Annual ice – forms along the coasts, eventually extending further offshore. It can remain as a solid sheet, or break off into pieces called “floes”.

Why doesn’t sea ice absorb a lot of sunlight? What effect does this have on the surrounding temperature?

*Because of its light colour, sea ice reflects light, rather than absorb it, as dark objects would.

Reflecting the sun’s energy rather than absorbing it, prevents the ice from melting.

What effect would decreased sea ice have on the temperature in the Arctic?

*Decreased sea ice results in less reflection and more absorption (decreased albedo). Ice melting allows more dark areas (water and land) to absorb heat energy and increase the temperature of the surrounding air.

Since 1978, the extent of annual average sea ice extent has shrunk by 2.7% per decade. At this rate, how long would it take to lose our sea ice?

*At this rate, assuming that the rate of melting won’t increase with more exposed water (which would probably happen), the sea ice will be gone in 37 years, or in 2015

How will the increase of Arctic air pollutants affect this rate?

*Arctic pollutants that are airborne form haze which like greenhouse gases trap the Sun’s energy, thereby increasing the air temperature. Increased air temperature would therefore amplify the melting of the sea ice.

List some ways that you as a student population could make a difference on this issue.

Do it!

Extensions

Write the chemical reactions of the air pollutants mentioned earlier, with water.

*Answers will vary based on the pollutant chosen.

How do the products in the above reactions affect the pH of the ocean?

*Theoretically acids lower the pH. However, there are other factors which must be considered, such as the equilibrium reactions of CO2 with water and bicarbonate.

Research to find out what companies/organizations are contributing to the type of pollutant you have mentioned. Write them a letter!

*This information will vary.

Dioxins are a major source of air pollution, and have serious health effects. Find out

-The major sources of dioxin

*Dioxins actually refer to a large group of chemicals that persist in our environment. The most toxic one is TCDD. They are produced as by-products from industrial processes that use chlorine. For example pesticide manufacturing and pulp and paper bleaching.

-The locations in the Arctic where it has been found

Dioxins have been found all through the Arctic – even in the Arctic snowcaps.

-The hazards to the health of native people

*The staples of the Inuit people – seals, walrus, and whales – all of which are at the tops of various food chains, have bioaccumulated large amounts of the top 12 most toxic chemicals, one of which is dioxin.

-Any types of efforts to resolve the problem

*Legislation has been passes to set maximum amounts of waste dioxin in bleaching processes by 1994 Organizations are working to reduce and eliminate dioxin production (eg.WHO), May 2010