1. Power Generation Siting fossil fuel power stations in mainly rural areas and distributing the pollution produced more evenly via tall chimneys has resulted in improved urban air quality, though they still remain a major source of pollution, mainly sulphur dioxide and nitrogen oxides. Better dispersion of pollutants emitted by tall chimneys leads to better dilution in the air and thus lower local concentrations of pollutants. This has however led to pollution being dispersed more widely and to transboundary air pollution. 2. Other Industry and waste disposal Although fossil fuel power plants are the major source of industrial air pollution in many countries, all industry and many businesses, large and small, can be significant local sources of a wide range of air pollutants. All waste has the potential to affect the environment adversely by contaminating the air, soil or water. Poorly managed waste disposal sites (landfill or incineration) can also pose a danger to public health, through all these routes. Air pollution from motor vehicles has, in many countries, replaced coal smoke as the major cause for concern; and the continuing growth in vehicle use means that efforts to reduce emissions from individual vehicles are in danger of being overtaken by increases in the volume of traffic. The air pollutants produced as a result of the use of motor vehicles present a two-stage problem: primary and secondary pollutants. Primary pollutants produced by petrol-powered vehicles include carbon monoxide, nitric oxide, benzene, particulate matter and lead. Much of the lead emitted by vehicles burning leaded petrol emerges as particles. Secondary pollutants produced as a result of the use of petrol-engined vehicles include nitrogen dioxide and ozone. 4. Domestic Sources As temperatures across the region plummeted, domestic burning of coal across northern China becomes the primary source of air pollution. Other important domestic sources of air pollution are: Stoves and cookers produce carbon monoxide. If ventilation is inadequate or appliances poorly maintained, CO may accumulate in dangerous concentrations. Nitrogen dioxide is also generated and concentrations in kitchens will usually exceed those outdoors when cookers are in use. Bonfires, garden incinerators and barbecues can be a significant local smoke and odour nuisance. Burning garden waste produces smoke, especially if it is damp and smouldering rather than dry and blazing. The smoke contains CO and other noxious and irritating compounds. Problems may be caused for asthmatics, bronchitis sufferers or those with heart conditions. Even if the immediate health risk is small, bonfires add to the general background level of air pollution. 5. Agriculture Agricultural practices can also be a significant source of nuisance, contributing both to local levels of air pollution and causing odour problems. The main sources of pollution are the burning of agricultural waste, or of crops in the field and large intensive livestock units. Depending on soil type and fertilisation, the nitrogen in the dung and urine of grazing cattle contributes 20-40% of nitrous oxide emissions from agricultural land; methane is also emitted by cattle and other ruminants; nitrous oxide and methane are of course both greenhouse gases. |
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