Air pollutants
When fuelMaterial that is used to produce heat, like coal, oil or gas. are burned, a number of atmospheric pollutantA toxic chemical or object that causes damage to the land, air or water. are produced. Here are some of the pollutants from burning fuels, and where they come from:
| Pollutant | Source |
| Carbon dioxide, CO2 | Complete combustion of any fuel containing carbon atoms |
| Carbon monoxide, CO | Incomplete combustion of any fuel containing carbon atoms |
| Particulate carbon, C (soot) | Incomplete combustion of any fuel containing carbon atoms |
| Unburned hydrocarbons | Hydrocarbon fuel molecules which have not been oxidised at all |
| Sulfur dioxide, SO2 | Combustion of a fossil fuel which contains sulfur impurities |
| Nitrogen oxides, NOx | Oxidation of nitrogen from the air inside the engine of a car, lorry, etc |
| Pollutant | Carbon dioxide, CO2 |
|---|---|
| Source | Complete combustion of any fuel containing carbon atoms |
| Pollutant | Carbon monoxide, CO |
|---|---|
| Source | Incomplete combustion of any fuel containing carbon atoms |
| Pollutant | Particulate carbon, C (soot) |
|---|---|
| Source | Incomplete combustion of any fuel containing carbon atoms |
| Pollutant | Unburned hydrocarbons |
|---|---|
| Source | Hydrocarbon fuel molecules which have not been oxidised at all |
| Pollutant | Sulfur dioxide, SO2 |
|---|---|
| Source | Combustion of a fossil fuel which contains sulfur impurities |
| Pollutant | Nitrogen oxides, NOx |
|---|---|
| Source | Oxidation of nitrogen from the air inside the engine of a car, lorry, etc |
Carbon monoxide as a pollutant
incomplete combustionBurning when there is a limited supply of air or oxygen. of a hydrocarbonA compound that contains hydrogen and carbon only. fuel occurs when there is not enough oxygen for complete combustionBurning in a plentiful supply of oxygen or air. Complete combustion of a hydrocarbon produces water vapour and carbon dioxide., caused by a poor supply of air. Less energy is released. Instead of carbon dioxide, you might get carbon monoxidePoisonous gas produced during incomplete combustion. or particulate carbon, known commonly as sootThe fine black particles, chiefly composed of carbon, produced by incomplete combustion of coal, oil, wood, or other fuels., or a mixture of both.
Carbon monoxide is a poisonous gas which binds to haemoglobinThe red protein found in red blood cells that transports oxygen round the body. in red blood cells, preventing them from carrying oxygen to the cells in the body. Carbon monoxide is colourless and has no smell, so it is very difficult to tell if it's being inhaled. At low doses it reduces the ability of the blood to carry oxygen, which puts a strain on the heart. At high doses, it can be fatal.
Particulates as a pollutant
Particulates (eg particulate carbon from diesel engines, dust from roads and industry) can cause health problems for humans because it irritates the lining of the lungs, eg it can make asthmaA disease that affects the respiratory system. worse. The smaller particulates are able to travel deeper into the lung tissue and cause damage that could lead to cancerA disease caused by normal cells changing so that they grow and divide in an uncontrolled way. The uncontrolled growth causes a lump called a tumour to form. and heart diseaseA wide range of conditions that affect the heart..
Sulfur dioxide as a pollutant
Some fossil fuels contain sulfur impurities. These fuels include:
- coal burnt in some power stations
- some diesel fuel burnt in ships and heavy vehicles
Sulfur dioxide is caused when the sulfur atoms are oxidised:
sulfur + oxygen 鈫 sulfur dioxide
S + O2 鈫 SO2
Sulfur dioxide then reacts with oxygen and water in moist air to make acid rainRain that contains dissolved acidic gases such as nitrogen oxides and sulfur dioxide., which is a dilute solution of sulfuric acid, H2SO4.
Acid rain harms and kills plants and animals, especially those that live in water. It can also damage man-made objects like statues and buildings.
NOx gases as pollutants
Nitrogen is not present in fuels, but the high temperatures and pressures inside a car engine can cause the nitrogen and oxygen in the air to react together to make oxides of nitrogen.
There are several compoundA substance formed by the chemical union of two or more elements. formed when nitrogen bonds with oxygen, but the two which are made inside engines are NO and NO2. These two pollutants are grouped together with the general formula NOx.
NOx gases can cause acid rain, and they also react in the atmosphere with other pollutants to make smogA type of air pollution that appears as a visible smoky fog which is very harmful to health.. Smog can have major health effects, causing asthma attacks and even death.
Question
Diesel sometimes contains sulfur impurities. List the pollutants which could be produced when it is burned incompletely inside a car engine.
Carbon monoxide, particulate carbon, sulfur dioxide and nitrogen oxides.