Acid rain or acid precipitation is the rain, snow, fog hail which has pH levels below 5.6, the average acidity of rain. The pH scale is used to measure the level of acidity by measuring the hydrogen ion concentration, were pH 1 is the strongest acid and pH 14 is the strongest base. Acids and bases of the same amount and strength can neutralise each other. Acid rain is caused by the release of oxides of sulphur (SO2) and nitrogen (NOx) which when combined with the moisture in the air, may fall as rain with acidity of sulphuric or nitric acids.
In Europe, the main cause of the acid rain is caused by the release of sulphur oxides. These are released when burning fossil fuels. Cars, power-plants, industries and burning coal and oil are the main contributories to the release of sulphur oxides. Nitrogen oxide is a result of any combustion or burning processes. The main source of emissions of nitrogen oxides are vehicles, residential and commercial furnaces and engines.
Some acid rain is caused naturally by volcanoes, forest fires and rotting vegetation. An aspect of acid rain that has made it an issue of great political controversy is that it can be transported by prevailing winds. Neighbouring or close-by countries may be polluting, but the precipitation may only occur in near countries. The sulphur and nitrogen oxides can also be moved and deposited without forming acid rain. This occurs when it doesn't combine with moisture in the air to make acids, so it is deposited often in the ground or in leaves.
This is also potentially harmful we may breathe this in, and the moisture in our throats or lungs may turn them into acids.
The problem of acid rain has been greatly ignored until quite recently, even though it was detected in the industrial revolution. Only 1990 was it declared the worst environmental hazard Europe, about 100 years after it started affecting our environment. The problem is affecting Northern Europe, Northern USA and Canada. Among the countries which most care about their environment is Sweden. However, acid rain is being deposited in their country from several areas.
Acid rain can alter the eco-system. The acid corrodes buildings, kills and weakens trees and damages crops. When it falls close to water sources, it may release aluminium or cadmium ions from the soil or eroded rocks. This causes all fish eggs to die out, and it will cause the fishes' gills to clog up with mucus, suffocating most the fish and making life in the waters extinct. Acid precipitation also kills amphibians and insects, completely altering the food chain and the eco-system and therefore killing off many other animals as well. Since acid rain can move and be deposited in different countries, the international relations between the countries that are polluting and suffering from acid rain will become tense. Acid rain is also managing to affect humans' health. Dry deposition and contamination of drinking water sources can cause respiratory problems, stomach upsets and cancers. Infra-structure and priceless historical monuments or sculptures are being deteriorated and is causing the United States over 2 Billions dollars in maintenance and restoration.
This being an international issue complicates any solution for one solution may not be apt or fair for other countries. Even though levels of sulphur dioxide have stabilized in Europe, it is still the greatest causer of acid rain. In the United States, 66% of the Sulphur dioxide is emitted by industries and factories. A possible solution that would greatly decrease the amount of sulphur dioxide released would be to purify the gas prior to releasing it through the factory chimney. Scrubbers or the technique of "FGD ", which is adding lime on the chimney of factories, would eliminate most impurities of the gases released or reduce the SO2 levels. This has been proved very effective because with just a 4% increase in price would reduce the sulphur dioxide levels by 60%. The problem with this solution is that it would make the factories' products more expensive and if other industries do not apply this same method, the clean factories would not be able to compete in terms of price. However, there is a solution to this problem. If every country co-operates, they could enforce a law where "dirty" factories have to pay additional taxes, obliging them not to pollute. This will lead on to another problem where factories in E.L.D.C's can not afford to place scrubbers or applying FGS. Nitrogen oxides are mostly released because of vehicles. Catalytic converters are chambers that are placed in the exhaust system of motor vehicles, and clean up pollutants before they exit the vehicle. This is very viable for economically more developed countries. Using more public transport, having more engine checks and enforcing a law to make it obligatory will decrease the amount of nitrogen oxides released. In my opinion, the most practical solution would be simply to use less, create new laws and to change habits. We could create laws for households with limits of energy allowed per member, and when it would be exceeded, the government could charge the extra energy at a higher rate. Cleaning up the acidity that has already affected our environment will be even more difficult. Acid lakes can be cleaned up with lime, but this is very expensive and requires frequent treatments. Preventing further acid rain is more important, for without it, this is just a short-term solution for acid rain will continue to acidify the rivers.