Reading Passage 3
A: In the late 1970s, people in northern Europe were observing a change in the lakes and forests around them. Areas once famous for the quality and quantity of their fish began to decline, and areas of once-green forest were dying. The phenomenon they witnessed was acid rain – pollutants in rain, snow, hail and fog caused by sulphuric and nitric acids.
B: The principal chemicals that cause these acids are sulphur dioxide and oxides of nitrogen, both by-products of burning fossil fuels (coal, oil and gas). A percentage of acid rain is natural, from volcanoes, forest fires and biological decay, but the majority is unsurprisingly manmade. Of this, transportation sources account for 40%; power plants 30%; industrial sources 25%; and commercial institutions and residues 5%. What makes these figures particularly disturbing is that since the 1970s, nitrogen oxide emissions have tripled. Each year the global atmosphere is polluted with 20 billion tons of carbon dioxide, 130 million tons of sulphur dioxide, more than three million tons of toxic metals, and a wealth of synthetic organic compounds, many of which are proven causes of cancer, genetic mutations and birth defects.
C: For natural causes of acid rain, nature has provided a filter. Naturally occurring substances such as limestone or other antacids can neutralise this acid rain before it enters the water cycle, thereby protecting it. However, areas with a predominantly quartzite- or granite-based geology and little top soil have no such effect, and the basic environment shifts from an alkaline to an acidic one. Recycled and intensified through the water table, acid rain has reached such a degree in some parts of the world that rainfall is now 40 times more acidic than normal – the same acidic classification as vinegar.
D: Environmentally, the impact is devastating. Lakes and the life they support are dying, unable to withstand such a battering. This has a direct effect on the animals that rely on fish as a food source. Certain species of American otter have had their numbers reduced by over half in the last 20 years, for example. Yet this is not the only effect. Nitrogen oxides, the principal reagent in acid rain, react with other pollutants to produce ozone, a major air pollutant responsible for destroying the effectiveness of farmland, making it significantly less productive. With scientists working on producing ever bigger and longer lasting genetically modified foods, some farmers are reporting abnormally low yields. Tomatoes grow to only half their full weight and the leaves, stalks and roots of other crops never reach full maturity.
E: Naturally it rains on cities too, eating away stone monuments and concrete structures, and corroding the pipes which channel the water away to the lakes where the cycle is repeated. Paint exposed to rain is not lasting as long due to the pollution in the atmosphere speeding up the corrosion process. In some communities the drinking water is laced with toxic metals freed from metal pipes by the acidity. After any period of non-use, we are encouraged to run taps for at least 60 seconds to flush any excess debris, as increased concentrations of metals in plumbing such as lead, copper and zinc result in adverse health effects. As if urban skies were not already grey enough, typical visibility has declined from ten to four miles, in many American cities, as acid rain turns into smog. Also, now there are indicators that the components of acid rain are a health risk, linked to human respiratory disease.
F: Acid rain itself is not an entirely new phenomenon. In the nineteenth century, acid rain fell both in towns and cities. What is new, and of great concern, is that it can be transported thousands of kilometres due to the introduction of tall chimneys dispersing pollutants high into the atmosphere, allowing strong wind currents to blow the acid rain hundreds of miles from its source. Thus the areas where acid rain falls are not necessarily the areas where the pollution comes from. Pollution from industrial areas of England are damaging forests in Scotland and Scandinavia. Acids from the Midwest United States are blown into northwest Canada. More and more regions are beginning to be affected, and given that 13 of the world’s most polluted cities are in neighbouring Asia, countries like Australia and New Zealand are increasingly under threat.
G: Transboundary pollution, the spread of acid rain across political and international borders, has prompted a number of international responses. International legislation during the 1980s and 1990s has led to reductions in sulphur dioxide emissions in many countries but reductions in emissions of nitrogen oxides have been much less, leading to the conclusion that without a cooperative global effort, the problem of acid rain will not simply blow away.