Michael McCarthy, The Independent 23 Jun 10;
Thirty years ago it was one of the great environmental issues, along with the hole in the ozone layer and CFC chemicals. Now acid rain may be making a comeback – but this time, there's a change in the chemicals responsible.
Nitrogen emissions from motor vehicles and agricultural fertilisers, are combining with rain to produce nitric acid, and are starting to replace the sulphuric acid resulting from power-station emissions as a major source of the environmental scourge of the 1970s and 1980s, according to American experts.
The result is a renewed and serious environmental risk for forests, rivers and wildlife, as nitric acid rain can – just like its sulphuric equivalent – kill plants, fish and insects by leaching important plant nutrients such potassium, calcium and magnesium from the soil. At the same time, it can help to liberate potentially toxic minerals such as aluminium, which can flow off into watercourses. The concern is surfacing in the US, where several scientists have voiced their worries in the current issue of the journal Scientific American.
But the problem exists in Britain and Europe too, especially in Scandinavia, which, because of prevailing westerly winds, receives much of the UK's air pollution. "The issue hasn't gone away," said Ed Dearnley, policy officer for air quality at the charity Environmental Protection UK.
In fact, many EU member states are not on course to meet new limits on nitrogen air pollution which come into force at the end of this year, under the 1999 Gothenburg Protocol, which attempts to do for air pollution what the 1997 Kyoto Protocol attempted to do for climate change: solve the problem by reducing emissions.
The UK is unlikely to meet its limits for NOx (oxides of nitrogen) under the EU National Emission Ceilings Directive, although by a smaller margin than many other countries. Britain expects to overshoot its NOx ceilings by less than 5 per cent, whereas France and Spain look like exceeding theirs by about 30 per cent.
In the US, although nitrogen pollution has been reduced, it has not gone down as much as sulphur pollution. Sulphur dioxide emissions decreased by almost 70 per cent from 1990 to 2008, but emissions of NOx went down only 35 per cent during the same period. Scientists "have grown increasingly aware of the consequences of the remaining nitric acid deposition", according to Professor William Schlesinger, president of the Cary Institute for Ecosystem Studies in Millbrook, New York.
Professor Schlesinger said it is clear that humans are adding nitrogen to the Earth's surface, and although researchers do not know yet where it all goes, "we do know that increasing concentrations of nitrogen in unexpected places will cause significant environmental damage that we will all learn to regret".
According to Scientific American, the Professor thinks that national arguments over climate change have allowed the US to ignore the nitrogen problem, which he predicts will be the next big environmental issue.
Atmospheric nitrogen is not only responsible for acid rain; when it falls to earth it also causes eutrophication, an excess of nutrients which can lead to algal blooms on lakes and can disrupt plant diversity by letting a very few plant species outcompete almost everything else.
Acid rain: An environmental crisis that disappeared off the radar
Michael McCarthy The Independent 23 Jun 10;
You can tell an environmental problem has gone off the radar screen when Friends of the Earth don't have anybody tracking it, and that's the case with acid rain. There is currently no acid rain campaigner at FoE in London (although they will cheerfully point you in the direction of an expert).
These days, the focus of green campaigners has switched almost entirely, away from air pollution to climate change. Yet a generation ago, acid rain was one of the highest-profile green issues, of concern to all the main campaigning environmental groups and to the general public, who were presented with apocalyptic visions of forests dying and lifeless rivers.
It was also the subject of angry argument between nations – not least between the Scandinavian countries, and Britain. In the mid 1980s, when the row was at its height, Norway and Sweden took very strong objection to the fact the acid rain they were suffering from, which was causing serious problems for their forests and lakes, was largely British in origin.
Much of Britain's electricity was then generated by big coal-burning power stations situated in northern England on the eastern side of the Pennines, such as Drax in Yorkshire. These plants burned enormous amounts of coal with a very high sulphur content, and the resultant sulphur dioxide emissions from the power station chimneys were blown by the prevailing westerly winds across the North Sea, transformed into sulphuric acid and deposited on the Scandinavian land mass.
For Britain it was unfortunately "out of sight, out of mind", and the Norwegians and Swedes were furious that the then Prime Minister, Margaret Thatcher, with Britain's Central Electricity Generating Board run by a Thatcher favourite, Walter Marshall, were long disinclined to take responsibility.
Eventually, however, Britain accepted it had to do something and at considerable expense, flue gas desulphurisation equipment, or sulphur "scrubbers", were fitted to all major power station chimneys. Since then atmospheric sulphur emissions have tumbled in Britain by about 85 per cent. But nitrogen is the new concern now.
