Acid rain 12
Acid rain 12Acid from the clouds
Lake Barkevatn in Aust-Agder county used to have healthy stocks of trout and perch. As a result of acid rain, the trout stock died out in the mid-1970s and the perch stock at the beginning of the 1980s.
� Precipitation that is polluted by sulphur dioxide (SO2) and nitrogen oxides (NOX) is known as acid rain.
� Acidity is measured in pH units: the lower the pH, the more acidic the substance. Unpolluted rain has a pH of roughly 5.6, but there are natural variations. Acid rain and snow, with a pH of about 4.4, has fallen in southern Norway for many years, causing serious environmental damage in many areas. The severity of the damage depends more on the total input of sulphur and nitrogen than on the acidity of each raindrop.
� More than 90 per cent of the acid rain that falls over Norway originates in other countries.
� Cuts in emissions have reduced the acidity of rain and snow recently. Total emissions of sulphur in Europe were reduced by more than 40 per cent from 1980 to 1993. In the same period, Norway's emissions were reduced by more than 70 per cent.
� As a result of higher precipitation in recent years, sulphur deposition has not dropped as much as might be expected from the reductions in emissions.
� Estimates of how much pollution the environment can absorb without damage are called critical loads.
� Sulphur, like nitrogen, is essential to all animals and plants. The natural sulphur cycle includes volcanic emissions, sulphate in sea salts, and sulphur compounds produced by marine organisms. On a global basis, emissions from such sources are of about the same order of magnitude as those from the combustion of fossil fuels (coal and oil), but like many other essential substances, sulphur is harmful in excessive amounts. Much of Europe and North America is suffering from sulphur deposition that exceeds critical loads as a result of the large amounts of such compounds generated by human activity. Critical loads are exceeded across more than one-third of Norwegian territory. Coal-fired power stations account for a large proportion of sulphur emissions in Europe.
� Nitrogen oxides (NOX) react to form nitric acid, another important component of acid rain, in the atmosphere. Until now, nitrogen compounds in precipitation have mainly been absorbed by plants or stored in the soil. Scientists fear that the amount of nitrogen that can be taken up in this way will be exceeded, thus intensifying acidification in some areas. Road traffic is responsible for more than half of all nitrogen emissions in Europe
Rivers and lakes are dying
In Germany, a mention of acid rain immediately makes people think of dying forests, whereas Norwegians associate it with the death of fish in lakes and rivers. Thousands of trout stocks have been lost...
To view the complete essay, you be registered.