Acid Rain:
Acid rain, first described in 1872 by an English Chemist, remains one of the industrialised worlds most intractable problems. What has taken humankind centuries to build, and nature millennia to evolve, is being degraded and destroyed in a matter of a few years.
When this mixture is washed out of the atmosphere by rain, snow crystals, or in the form of dry particles, it increases the acidity of freshwater lakes and streams, and in some cases soils too. This consequently decreases their pH values. This pH scale measures acidity and alkalinity. A solution with a pH of 7 is neutral, anything above this is alkaline, and anything beneath is acidic. It is a logarithmic scale, so every full point is equivalent to factor of 10. Thus a pH of 6 is 10-times more acidic than neutral, and a pH of 5 is 100-times more acidic than neutral.
- Acid Rain and the ‘Environmental Toll’
Acidic smogs are destroying the magnificent historic buildings of Krakow, Poland, a world heritage site; ornate facades are disintegrating, walls and roofs are weakening. Acid rain and other airborne pollutants are biting into the marble of Athens’ monuments; experts say that more damage has been done to the Parthenon in the last 25-years than in the previous 2,400. The masonry of Cologne cathedral in Germany is being eaten away, many of Europe’s stained glass windows are fading, and many libraries in the United States have had to be fitted with special anti-pollution equipment to preserve many precious books.
Nearly, a quarter of Sweden’s 90,000 lakes are acidified to some extent; 4,000 of them so severely that no fish are thought to survive in them. Some 100,000 Kilometres of its rivers and streams are also affected. In the southern half of Norway, four-fifths of the lakes and streams are either technically dead or on the critical list; authorities say that fish have been destroyed in lakes covering a total of 13,000 square kilometres.
Thousands of lakes in the eastern United States – including at least 10% of all those in the Adirondack Mountains – are too acid to support fish. More than 300 lakes in Canada’s Ontario province are estimated to have pH values lower than 5 – the level at which most fish die – and another 48,000 are recorded as being threatened. Trout and Salmon no longer reproduce in nine acidic rivers in Nova Scotia.
Researchers in Germany believe that acid rain is one of the causes of Waldsterben (tree death), which afflicts more than half of the country’s forests. Acid deposition is also thought to be one of the main agents of the decline of Switzerland forests; 43% of the conifers in its central alpine region are dead or dying.
More than 900,000 square kilometres of European Russia is also thought to be affected by acid rain. The former East Germany has the highest per capita sulphur dioxide emissions in the world, and Poland, Czechoslovakia and Romania are among the most polluted countries on the earth. China, the world’s third largest emitter of sulphur dioxide, has growing problems in its southern provinces, and acid rain damage is spreading in other Third World countries like India, Nigeria, Columbia, Venezuela and Brazil.
- A man-made problem -
Although natural processes such as volcanic eruptions can cause acid rain, natures own doses of sulphur and nitrogen oxides are dwarfed by industrial pollution. Ever year, around 100-million metric tonnes of sulphur dioxides are released across the globe, with Europe and North America accounting for 38-million metric tonnes. More than 90% of the deposited sulphur is manmade. The countries belonging to the Organisation for Economic Cooperation and Development (OECD) generate around 37 million metric tonnes of nitrogen oxides every year.
Rainfall is naturally acidic, with a pH of around 5.6. But man’s pollution routinely increases acidity up to 100-times the natural level in industrialised countries. Data gathered by the European Monitoring and Evaluation Programme shows that the average pH values in central Europe are 4.3 or below. According to the OECD, polluted areas in Scandinavia, Japan, central Europe and eastern North America have annual pH values that can fall as low as 3.5.
Ever year, Norway experiences some rainfall that is as acidic as lemon juice. In the US, precipitation as acid as vinegar has fallen on Kane, Pennsylvania, and ‘rain’ with a pH value almost equivalent to battery acid once fell on Wheeling, West Virginia.
The effects of acid rain would be much more widespread if nature had not provided many areas with their own protection. Alkaline soils, like those covering most of Midway US and much of Southeast England, can resist acid fallout because the calcium in the soil neutralises – or ‘buffers’ – the acids; so can lakes which have beds of limestone or sandstone. On the other hand, where lakes and earth sit on thin glacial soils or thick slabs of granite – as in most of Scandinavia, Scotland and Central Europe – this buffering capacity is greatly reduced. It is these sensitive areas that are hardest hit by acid deposition.
- Hidden Killers -
Acid Rain, in itself, kills few fish. Sensitive species like salmon, trout, minnows and arctic char succumb to the lethal water chemistry which acid rain fosters. Acid waters contain increased concentrations of toxic heavy metals such as mercury, aluminium, manganese, lead and zinc. It is aluminium – the most common metal found in soils – leached into lakes and streams that really deliver the final blow. Aluminium toxicity peaks at around pH value 5. It clogs fish’s gills, causing them to suffocate.
Research shows that acidity of forest soils has increased five- to 10-fold over the past 20 to 50 years across vast areas of Europe and eastern North America. Acid rain leaches crucial nutrients such as potassium, calcium and magnesium from soils, depriving trees and other vegetation of these life-supporting elements. If sufficient stocks of soil nutrients are not available, trees become more susceptible to climatic stresses like frost and winter damage, as well as damage from other pollutants.
Acid rain has been linked to the alarming decline of sugar maples in northeast US and eastern Canada. Surveys carried out in Quebec province showed that nearly 50% of all sugar maple stands were affected by Waldsterben-like systems of dieback. Certainly if not reversed, Canada’s maple syrup industry – worth in the region of $80 million a year – could collapse.
- Conservation efforts: the acid test -
The costs of acid rain damage are difficult to assess. But it has been estimated that damage to metals, buildings and paint in the OECD member countries costs around $20 Billion annually. This does include costs of dead forests, acidified lakes or damaged crops.
By 1990, Sweden had added lime to some 6,000 lakes, covering more than 75% of the total acidified lake area in the country, in an effort to neutralise the acid and bring them back to life – at a cost of nearly $15 million a year. This, however, is at best a stopgap measure, mitigating the effects of acid rain but failing really to tackle the causes.
The Convention on Long Range Transboundary Air Pollution, promulgated by the United Nations Economic Commission for Europe, calls for reductions in sulphur dioxide emissions at source. It covers both West and East Europe and was ratified and brought into effect in 1983. At a meeting in Helsinki in 1985, a protocol mandating sulphur dioxide reductions of 30% by 1993 (using 1980 as the base year) was opened for signature and was quickly endorsed by 21-countries. A second protocol freezes nitrogen oxide emissions.
The European Community (EC) had gone further. Large fossil fuel power plants have had to cut emissions of sulphur dioxide by around 40% since 1998 and extending to 60% reductions by 2003. Austria, Germany and Switzerland had committed themselves to a two-thirds reduction by 1995 and empirical data available via the OECD shows that nitrogen oxides have been cut by the targets set of 30% by the end of 1998 in 12 Western European Countries.
European directives set new conditions that by the end of 1993; all new cars sold in EU countries will have to be fitted with catalytic converters that reduce emissions of nitrogen oxides and other pollutants.
Certainly, the conclusion of the author is that many industrialised countries are finally beginning to get to grips with the pollution that causes acid rain; even the US and the UK, which for a long time resisted controls, are taking action to reduce emissions. I do say however and warn that greater cuts are needed; sulphur dioxide emissions, for example, need to be cut by 90%. This is not unreasonable because until this happens, the scourge of acid rain will continue to spread and manifest itself.
© Copyright MarkDowe, 2007
