Understanding the different sorts of pollution

Kimberley & Julian
Balwyn High School
Australia

Before I begin on this topic, I have to ask you all a question: what is pollution? Would it be an undesirable state of the natural environment being contaminated with harmful substances as a consequence of human activities? If that were your answer, then you would be right. There are many different kinds of pollution that damage our planet in different ways.

Air pollution

The moment you get out of the house and on to the road you can actually see the air around you getting polluted. Different sources of such pollution include the clouds of smoke from the exhausts of buses, cars, or scooters, or smoke billowing from a factory chimney and fly ash, which is full of oxide and can be used as a raw material for different industries. Speeding cars also cause dust to rise from the roads. Natural phenomena, such as the eruption of a volcano and even someone smoking a cigarette, can also cause air pollution.

The pollution from exhaust gases of vehicles is responsible for 60 per cent of all air pollution and up to 80 per cent of the pollution in cities. There are a large variety of harmful chemicals present in these gases, with lead being one of the most dangerous. The combustion of coal without special precautions can have serious consequences. If winds do not blow away the poisonous gases, they can have fatal effects and may lead to death.

Acid rain is the term for pollution caused when sulfur and nitrogen dioxides combine with atmospheric moisture to produce highly acidic rain, snow, hail, or fog. The acid eats into the stone, brick and metal particles and pollutes water sources.

Water pollution

Some types of water pollutants can occur through natural processes, but they are mostly a result of human activities. We use water daily in our homes. In the United States the average consumption is about 150 gallons per day, per person. The used water of the community is called waste water or sewage. If it is not treated before being discharged into waterways, then serious pollution is the result. Water pollution also occurs when rain water runs off from urban industrial areas, agricultural land and mining operations and makes its way back to rivers, lakes, or oceans and into the ground. When water is discharged after having been used in production processes, it may contain acids, alkalis, salts, poisons, oils and, in some cases, harmful bacteria. Mines, especially gold and coal mines, are responsible for large quantities of acid water. Agricultural pesticides, fertilisers and herbicides may wash into rivers and stagnant water bodies. Sewerage, domestic waste and farm waste are often allowed to pollute rivers and dams.

There are also different types of water pollutants, which can be classified as microbiological, chemical, oxygen-depleting substances, particular nutrients and suspended matter. We will now look at these in more depth.

In terms of microbiological pollutants, disease-causing (pathogenic) microorganisms, like bacteria, viruses and protozoa, can cause swimmers to get sick. Fish and shellfish can become contaminated and people who eat them can become ill. Some serious diseases like polio and cholera are waterborne.

A whole variety of chemicals from industry, such as metals and solvents, and even chemicals, which are formed from the breakdown of natural wastes (ammonia, for instance) are poisonous to fish and other aquatic life. Pesticides used in agriculture and around the home, such as insecticides for controlling insects and herbicides for controlling weeds, are other types of toxic chemicals. Some of these can accumulate in fish and shellfish and poison the people, animals, and birds that eat them. As well as being toxic, materials like detergents and oils float and spoil the appearance of a water body and many chemical pollutants also have unpleasant odours. The Niagara River, between the US and Canada, even caught fire at one time because of flammable chemical wastes discharged into the water.

Many wastes are biodegradable, that is, they can be broken down and used as food by microorganisms like bacteria. We tend to think of biodegradable wastes as being preferable to non-biodegradable ones, because they will be broken down and not remain in the environment for a very long time. Too much biodegradable material, though, can cause the serious problem of oxygen depletion in receiving waters. Like fish, aerobic bacteria that live in water use oxygen, which is dissolved in the water when they consume their 'food'. (The oxygen in the compound H2O, water, is chemically bound, and is not available for respiration). But oxygen is not very soluble in water. Even when the water is saturated with dissolved oxygen, it contains only about 1/25 the concentration that is present in air. So, if there is too much 'food' in the water, the bacteria that are consuming it can easily use up all of the dissolved oxygen, leaving none for the fish, which die of suffocation.

Once the oxygen is gone, other bacteria that do not need dissolved oxygen take over. But while aerobic microorganisms - those which use dissolved oxygen - convert the nitrogen, sulfur, and carbon compounds that are present in the wastewater into odourless, and relatively harmless, oxygenated forms like nitrates, sulfates and carbonates, these anaerobic microorganisms produce toxic and smelly ammonia, amines, and sulfides, and flammable methane (swamp gas). Add in the dead fish, and you see why we don't want large amounts of biodegradable materials entering lakes and streams.

The elements phosphorus and nitrogen are necessary for plant growth, and are plentiful in untreated wastewater. Added to lakes and streams, they cause nuisance growth of aquatic weeds, as well as 'bloom' of algae, which are microscopic plants. This can cause several problems. Weeds can make a lake unsuitable for swimming and boating. Algae and weeds die and become biodegradable material, which can cause the problems mentioned above and below. If the water is used as a drinking water source, algae can clog filters and impart unpleasant tastes and odours to the finished water.

Suspended matter

Some pollutants are dissolved in waste water, meaning that the individual molecules or ions (electrically charged atoms or molecules) of the substance, are mixed directly in between the molecules of water. Other pollutants, referred to as particulate matter, consist of much larger, but still very small, particles, which are just suspended in the water. Although they may be kept in suspension by turbulence, once in the water, they will eventually settle out and form silt or mud at the bottom. These sediments can decrease the depth of the body of water. If there is a lot of biodegradable organic material in the sediment, it will become anaerobic and contribute to the problems mentioned above. Toxic materials can also accumulate in the sediment and affect the organisms, which live there, and can build up in fish that feed on them, and so be passed up the food chain, causing problems all the way along. Also, some of the particulate matter may be grease or be coated with grease, which is lighter than water, and float to the top, creating an aesthetic nuisance.

Noise pollution

Noise pollution, or unwanted sounds that are carried by the air, has an irritating and detrimental effect on humans and other animals. Careful planning of streets and buildings in towns and better control over noisy vehicles may add to the control of noise pollution.

Tobacco smoke

Tobacco smoke is one of the major forms of pollution in buildings. It is not only the smoker who is affected, but everyone who inhales the polluted air. There is a very strong connection between smoking and lung cancer. Bronchitis is common among smokers. The unborn babies of mothers who smoke also suffer from the harmful effects of smoking.

Land pollution

Land pollution is the degradation of the Earth's land surface through misuse of the soil by poor agricultural practices, mineral exploitation, industrial waste dumping, and indiscriminate disposal of urban wastes. It includes visible waste and litter as well as pollution of the soil itself. Soil pollution is mainly due to chemicals in herbicides (weed killers) and pesticides (poisons which kill insects and other invertebrate pests). Litter is waste material dumped in public places such as streets, parks, picnic areas, at bus stops and near shops. The accumulation of waste threatens the health of people in residential areas. When waste decays it encourages household pests and turns urban areas into unsightly, dirty and unhealthy places to live in.

But now the big question is how to stop all this so that we can protect this planet of ours and live on it for many years to come.

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