Page 43 - Curriculum Visions Dynamic Book

 Gases and dust are collected in special hoods attached to each electrolytic cell.
acidity: a general term for the strength of an acid in a solution.
buffer: a chemistry term meaning a mixture of substances in solution that resists a change in the acidity or alkalinity of the solution.
clay: a microscopically small plate-like mineral that makes up the bulk of many soils. It has a sticky feel when wet.
ion: an atom, or group of atoms, that has gained or lost one or more electrons and so developed
an electrical charge.
pH: a measure of the hydrogen ion concentration in a liquid. Neutral is pH 7.0; numbers greater than this are alkaline, smaller numbers are acidic.
Aluminium and acid rain
Aluminium is insoluble if the pH of the soil is greater than 5. Only acid soils, such as podzols, which occur in areas of high rainfall or on acid parent materials, are therefore likely to cause aluminium to go into solution. So, under normal circumstances, aluminium compounds are not released into the soil or the water supply and are only taken up in small amounts by the body. More recently, the phenomenon of acid rain has changed this in some areas.
Acid rain occurs when polluting gases created by factories and vehicles, mix with water vapour in the air and then eventually fall as acidic raindrops or snow. This extra acid gets into the soil where it begins to act on the abundant aluminium in the
clay crystals.
Acid rain releases aluminium compounds, which can then be taken up by plant roots where they can damage or even kill plants.
The aluminium compounds also flow into nearby rivers and lakes where they are absorbed by fish and other animals. Again the effects can be disastrous. In fact, many plants and animals die of aluminium poisoning. It is important to remember, though, that the real problem is not the presence of aluminium but the acid rain we produce by polluting the atmosphere with sulphur and nitrogen compounds.
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