Air and Pollution幻灯片.pptVIP

The Importance of Air Air is a mixture of gases It is important: for life; contains oxygen which supports life, water and carbon dioxide which green plants need to make food for the protection from ultraviolet radiation of the sun (ozone layer in the upper atmosphere) for the burning of fuels for the production of heat energy in power stations as a source of nitrogen, oxygen and argon (noble gas) Composition of Air Nitrogen ? 78% Oxygen ? 21% Carbon dioxide ? 0.03% Argon and rare gases ? 1% Water vapour ? Variable (0 – 5%) argon (1%) oxygen (21%) nitrogen (78%) Air Pollution Pollutants are substances that may harm living things or damage non-living things. Some common atmospheric pollutants are: carbon monoxide methane nitrogen oxides (NO and NO2) ozone sulfur dioxide unburned hydrocarbons Carbon monoxide Colourless and odourless gas Comes from the incomplete combustion of fuel in vehicles; all new motor cars in Singapore are fitted with catalytic converters; oxidises CO to CO2 Can be absorbed by haemoglobin in the blood, thus blood can no longer absorb O2 Extra amounts of CO result in tiredness, headaches, heart damage and small amounts can be lethal Methane Small amounts of methane are naturally present in the atmosphere; bacterial decay of vegetation and other sources Increasing amount of methane in recent years observed; human activities such as agriculture, mining and waste disposal Methane (heat-trapping gas) causes ‘greenhouse effect’ / global warming Rice fields are a major source of methane Oxides of Nitrogen Oxides of nitrogen (NO and NO2) are produced naturally in lightning and forest fires Excess man-made production of oxides of nitrogen is harmful; found inside motorcar engines, power stations and industries Damage people’s lungs and react with other pollutants to form ozone Preventive measure: motorcars are fitted with catalytic converters to reduce oxides of nitrogen to N2 Ozone Ozone, O3, at ground level is a nasty pollutant Irri