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International Co-operation to Reduce Air Pollution

Introduction

Acid rain, or acid deposition as it should be correctly termed, is one of the major environmental issues of our time. Acid rain however, is not a new problem. In the mid 19th century, a Scottish scientist, Robert Angus Smith, began to study the effects of air pollution in Manchester where he coined the term "acid rain" to describe his findings. In Smith's time, acid rain fell in both towns and cities and downwind from them but now, following Clean Air Acts, levels of smoke and sulphur dioxide have been greatly reduced. Gaseous and particulate airborne pollutants are now dispersed higher into the atmosphere via tall chimney stacks. Other sources of pollutants such as vehicle exhausts may also be transported high into the atmosphere, depending on weather conditions.

Complex chemical reactions occur over time in the atmosphere including the formation of sulphuric and nitric acids, leading to the deposition of acidic precipitation. Because pollutants can be carried many hundreds of kilometres by winds, acid pollutants emitted in one country may be deposited as acid precipitation in other countries. Acid deposition has become an international problem. This problem is highlighted by the fact that emission of a particular pollutant from one country does not equal the deposition of that pollutant in the same country. Some countries emit small quantities of pollutants yet deposition can be several times greater, for example Norway, Sweden, Austria and Switzerland. Other countries such as Bulgaria, Italy and the UK emit more pollution than is deposited in their country because of prevailing wind directions.

Within Europe, emissions of air pollutants vary greatly, depending upon many factors such as size of population, degree of industrialisation, pollution control equipment used, agricultural practices, number of vehicles and political attitudes on environmental issues. The tables below show emissions (and deposition) of sulphur and nitrogen.

Estimated emissions and deposition of sulphur and nitrogen for European countries: 1990 and 1998

Reducing European Emissions

Sulphur Dioxide

In the late 1970s, the United Nations Economic Commission for Europe (UNECE) set up an international convention concerning Long Range Transboundary Pollution. In 1984 and 1985 most UNECE members agreed to reduce sulphur dioxide emissions by 30% (on 1980 levels) by 1993. This was called the 30% club. All of the countries that signed the Protocol achieved this reduction, and many of those that did not sign, have met these reductions. Austria greatly exceeded their target reduction by achieving an 82% reduction, whilst the UK achieved a 35% reduction. Only two countries increased their emissions, Croatia (20%) and Greece (27%).

In June 1994, a number of European countries signed the second Protocol for sulphur. Most of the western European countries have agreed to reduce sulphur emissions by between 70 and 80% by the year 2000 (against 1980 levels) whilst eastern European countries generally have a lower target of between 40 and 50% (against 1980 levels).

Overall, emissions of sulphur dioxide in Europe are estimated to have fallen by 25-30% between 1980 and 1990 (compared with 75% in the UK). If the signatories of the 1994 Protocol achieve their target reductions, European sulphur dioxide emissions are estimated to fall 47% by 2005 and 51% by 2010 (on 1980 levels).

Nitrogen Dioxide

The Sofia Protocol for reducing nitrogen oxide emissions was set up in 1988. This required all countries that signed the Protocol to stabilise emissions of NOx (against 1987 levels) but some countries committed themselves to 30% reductions by 1998 (against levels of any year between 1980 and 1986). However, many of these countries are unlikely to meet these targets; several countries such as Spain and Italy have increased their NOx emissions between 1987 and 1993 by 41% and 8% respectively.

Targets for Combustion Plants

In 1988 a Directive was introduced for EC countries which requires Large Combustion Plants over 50MW in size to reduce emissions of SO₂ and NOx by varying percentages by 1998 and 2003 (against 1980 levels). For the UK, reductions of 60% SO₂ by 2003 and 30% NOx by 1998 have been set. The UK is well on course to exceed both targets through new gas-fired power stations (which produce small quantities of SO₂ and NOx) replacing coal fired power stations, and flue gas desulphurisation equipment fitted to Drax and Ratcliffe-on-Soar power stations.

Vehicle Emissions

In addition, all cars sold within the European union from 1993 onwards have to be fitted with a catalytic converter to help reduce emissions of vehicular pollutants. Many non-EU countries also require catalytic converters to be fitted to vehicles sold within their countries.

Gothenburg Protocol

The most recent UNECE Convention on Long Range Transboundary Air Pollution protocol was signed by 27 countries in December 1999. The Gothenburg Protocol, designed to Abate Acidification, Eutrophication and Ground-level Ozone aims to cut emissions of four pollutants: sulphur dioxide (SO₂), nitrogen oxides (NOx), volatile organic compounds (VOCs), and ammonia (NH₃), by setting country-by-country emission ceilings to be achieved by the year 2010. The table below lists the countries that have agreed to sign the 1999 Protocol and the expected emissions reductions by 2010.

Conclusion

Although SO₂ emissions in Europe have been falling steadily over recent years, NOx emissions rose during the 1980s and have only recently begun to fall at a slower rate than was anticipated. Acid rain will therefore continue to be a problem in Europe until these emissions can be dramatically reduced.