4.3: Air pollution

by Emily and Josh

Objectives•Students should learn:

•that air can be polluted with smoke and gases, such as sulfur dioxide, which contributes to acid rain

•that acid rain may damage trees

•that plants and animals cannot survive if the water in rivers and lakes becomes too acidic

•that tiny solid particles polluting the air can cause global dimming

Outcomes•Most students should be able to:

•describe how acid rain is formed

•describe some of the effects of acid rain on living organisms

•explain how air pollution can result in global dimming.

•Some students should also be able to:

•analyse and interpret scientific data concerning the effects of acid rain.

Carbon Dioxide

Sulfur dioxide and nitrogen oxides

CFCs

Air pollution

Global Dimming● Caused by an increase in the number of tiny solid particles in the

air, which reflect sunlight so less light hits the surface of the Earth, causing a dimming effect. The temperatures on the Earth’s surface cool down.

Sulfur products from the burning of fossil fuels are part of this problem, and products from any other type of burning.

In Europe, where sulphur emissions and smoke are controlled, the dimming effect can even be reversed, but in developing countries it continues to get worse as air pollution grows.

What causes acid rain● Fossil fuels burnt- sulphur dioxide

released into atmosphere (from the reaction between the sulphur impurities in the fossil fuels, and oxygen in the air.) Nitrogen oxides are released at high temperatures (e.g. in car engines).

● Sulphur dioxides and nitrogen oxides dissolve in rainwater and react with oxygen in the air to form dilute nitric acid and sulphuric acid.

● This causes acid rain which has been measured at a pH of 2.0, more acidic than vinegar.

What damage does acid rain cause● Acid rain dissolves the nutrients and helpful

minerals in the soil, washing them away before trees and other plants can use them to grow.

● Acid rain makes waters acidic. Many fish and plant species can’t survive at such a low pH.

● The rain causes alumium to be released from the soil and washes it into lakes and rivers, where it is absorbed.

● Fish population numbers are reduced, and the dead or poisoned fish are eaten by animals higher up the food chain who rely on these fish as a food source. These animals are then poisoned also.

Acid rain effects on cressAcid rain kills all of the leaves that it lands on. Once the hydrogens are gone from the sulfuric acid, the sulfate that is left will bind with minerals and nutrients in the seed and remove them from use by the plant. There are many other things that go on as a result of the presence of sulfuric acid in the plant, but the above are some of the most obvious and important.

Things that can be done to reduce acid rain

● International agreements to reduce sulfur dioxide pollution.

● Energy efficiency means less coal burned to make electricity.

● Ultra low sulfur petrol.● Alternative energy sources

like natural gas, solar, wind farms and nuclear.