Pollutants

Pollutants

Engineering activities are a major source of pollutants and many types of pollution. Air, soil, rivers, lakes and seas are all, somewhere or other, polluted by waste gases, liquids and solids discarded by the engineering industry. Because engineering enterprises tend to be concentrated in and around towns and other built-up areas, these tend to be common sources of pollutants.

Electricity is a common source of energy and its generation very often involves the burning of the fossil fuels: coal, oil and natural gas. In so doing, each year, billions of tonnes of carbon dioxide, sulphur dioxide, smoke and toxic metals are released into the air to be distributed by the wind. The release of hot gases and hot liquids also produces another pollutant: heat. Some electricity generating stations use nuclear fuel that produces a highly radioactive solid waste rather than the above gases.

The generation of electricity is by no means the only source of toxic or biologically damaging pollutants. The exhaust gases from motor vehicles, oil refineries, chemical works and industrial furnaces are other problem areas. Also, not all pollutants are graded as toxic. For example, plastic and metal scrap dumped on waste tips, slag heaps around mining operations, old quarries, pits and derelict land are all non-toxic. Finally, pollutants can be further defined as degradable or non-degradable. These terms simply indicate whether the pollutant will decompose or disperse itself with time. For example, smoke is degradable but dumped plastic waste is not. Figure 1.22 shows a typical example of an industrial process that generates airborne pollutants.