AIR POLLUTION AND ACID RAINS

Without air there can be no life. Without air of good quality there cannot be a healthy life. Air pollution is an old problem, which has in this century assumed wide economic and social significance. Perhaps the first general realisation of the new dangers came with the great London smog of December 1952. For five days the capital of England was enveloped in a grey shroud, and over 4 thousand people had died and incalculable numbers had suffered a worsening of bronchitis and heart disease.

An average person requires over thirty pounds of air a day or about six pints every minute. Daily the individual draws 26000 breaths, between 18 and 22 each minute, many of which are of filthy air. The lungs of town inhabitants are usually greyish in colour, those of country people are normally pale pink.

The air is being polluted by acid gases, dust, petrol and diesel fumes and poisonous chemicals. These come from cars, factories and power plants.

Of all the pollutants, that taint the air, fine suspended particulate matter, sulphur dioxide and ozone pose the most wide-spread and acute risks. However, airborne lead pollution, coming from car exhausts, is a critical concern in many cities as well.

PARTICULATE POLLUTION

 Suspended particulate matter is nearly ubiquitous urban pollutant. It is a complex mixture of small and large particles of varying origin and chemical composition. Larger particles, ranging from 2,5 microns to 100 microns in diameter, usually comprise smoke and dust from industrial processes, agriculture, construction and road traffic, as well as plant pollen and other natural sources. Smaller particles – those less than 2,5 microns in diameter – generally come from combustion of fossil fuels. These particles include soot from vehicle exhaust, which is often coated with various chemical contaminants or metals. They also include fine sulphate and nitrate aerosols that form when sulphur dioxide and nitrogen oxides condense in the atmosphere. The largest source of fine particles is coal-fired power plants, but auto and diesel exhaust are also prime contributors, especially along busy transportation corridors.

The health effects of particles are strongly linked to their size. Small particles, such as those from fossil fuel combustion, are most dangerous, because they can be inhaled deeply into the lungs, setting in areas, where the body’s natural clearance mechanisms can’t remove them. The constituents in small particles are more chemically active and may be acidic as well and therefore more damaging.

Particulate pollution causes acute changes in lung function, respiratory illnesses, heart decease and aggravation of asthma and bronchitis. During major pollution events, when particulate levels in the air increase up to 200 micrograms of particulate matter per cubic meter, daily mortality rates could increase as much as 20 per cent.

 ACID RAINS

Other very dangerous pollutants are sulphur and nitrogen oxides. These gases are released by factories and power plants when fossil fuels are burned and by cars. These oxides reach high into the atmosphere and mix with water and other chemicals to form rain that can be as acid as vinegar. Acid rains are responsible for the decline of many forests. Tiny droplets of acid attack plant leaves, disrupting the production of chlorophyll. It also weakens the tree by altering the chemistry of the soil that surrounds its roots.

Acid falls down to earth as rain and snow. Black snow, as acid as vinegar, fell in Scotland in 1984.

Acid rain affects everything it falls on. Rivers, lakes and forests are at risk throughout Europe and North America. In Sweden more than 18000 lakes have become acidic, 4000 of them very seriously indeed. This kills fish and drives out fish-eating wildlife.

Forests are particularly badly affected by acid rain and in many places previously green, luxuriant trees show bare branches at the top, stripped of foliage. In West Germany 50 per cent of trees are affected and, unless some curb is placed on pollution, the figure is certain to rise. In Austria, if nothing is done, scientists and environmentalists have predicted that there will be no trees left by the end of the century.

There is a possibility that damage to ecosystems from acid deposition may be more fundamental and long-lasting than was first believed. Scientists now report that acid rain leaches as much as 50 per cent of the calcium and magnesium from the forest soils. These minerals neutralise acids and are essential for plant growth. If soil chemistry is changed in this way, it may take many decades for all linked ecosystems to recover. Besides this, acid rain releases heavy metals and other toxic substances, providing a persistent source of toxicity to surrounding vegetation and aquatic life.

Buildings “die” too. Some of the most beautiful historic buildings in the world are being eaten away by the dilute acid, rained on them. Notre Dame, Cologne Cathedral and St Paul’s Cathedral have all been damaged.

A major problem with air pollution is that it does not obey national boundaries. The planet’s wind cycles and currents can carry pollution hundreds of miles away from its original source. So Britain is a large contributor to air pollution in Sweden and creates more for Norway than Norway does itself. The pollutants of the USA end up on the eastern coast of Canada.

Acid rain emerged as a concern in the I960s with observations of dying lakes and forest damage in Northern Europe, the United States and Canada. It was one of the first environmental issues to demonstrate how the chief pollutants – oxides of sulphur and nitrogen – can be carried hundreds of miles by winds before being washed out of the atmosphere in rain, snow and fog.

As evidence grew of the links between air pollution and environmental damage, legislation to curb emissions was put in place. The 1979 Geneva Convention on Long-Range Transboundary Air Pollution set targets for reduction of sulphur and nitrogen emissions in Europe that have largely been achieved. The 1970 and 1990 Clean Air Acts have led to similar improvements in the USA.

Many nations have adopted air quality standards to safeguard the public against the most common pollutants. These include sulphur dioxide, carbon monoxide, suspended particulate matter, ground-level ozone, nitrogen dioxide and lead – all of which are tied directly or indirectly to the combustion of fossil fuels. Substantial investments in pollution control have lowered the levels of these pollutants in many cities of some developed countries. But poor air quality is still a major concern throughout the industrialised world.

Meanwhile, urban air pollution has worsened in most large cities in the developing world, a situation driven by population growth, industrialisation and increased vehicle use. Despite pollution control effects, air quality has approached the dangerous levels, recorded in London in the 1950s, in such megacities as Delhi, Jakarta and Mexico City.

In some parts of Asia, such as Southeast China, Northeast India, Thailand and the Republic of Korea, and in the Pacific region acid rain is now emerging as a major problem. In the Asia region the use of sulphur-containing coal and oil is very high. In 1990 34 million metric tons of sulphur dioxide were emitted there, which is over 40 per cent more, than in North America. The effects are already being felt in the agriculture. In India wheat growing near a power plant suffered a 49-per cent reduction in yield. Other ecosystems are also beginning to suffer. Pines and oaks in acid rain-affected areas of the Republic of Korea showed significant declines in growth rates since 1970.

Many countries in the world are trying to solve the problem of air pollution in various ways, either by trying to burn fossil fuels more cleanly or by fitting catalytic converters to their cars, so fewer poisonous gases are produced. In some countries, like Sweden for example, new power plants use a method called fluidised bed combustion, which cuts sulphur emission down by 80 per cent. In Germany sulphurous smoke is sprayed with lime to produce gypsum, which is then used for building roads. Developing technologies like this may raise the price of electricity a little, but will save millions of trees, plants and animals and human health.

Answer the questins:

1. When did people realise a new danger for their health? What kind of danger is it?

2. Why are the lungs of town inhabitants greyish in colour?

3. What pollutants pose the most wide-spread and acute risks?

4. What does suspended particulate matter?

5. What are the sources оf large particles? small particles?

6. Which particles are the most dangerous and why?

7. What are the effects of particulate pollution?

8. Which gases cause acid rain?

9. What are the sources of these gases?

10. How does acid rain form?

11. How does acid rain affect the plants? buildings? lakes and soil?

12. What is the main problem with air pollution? Prove your statement.

13. How do people try to curb air pollution?

14. In what parts of the world acid rain is emerging now as a major problem?

GLOSSARY:

sulphur dioxide - двуокись серы

airborne - воздушный

lead pollution - загрязнение свинцом

car exhaust - выхлопные газы

combustion - сгорание

fossil fuel - ископаемое топливо

contaminant (pollutant) -  загрязняющее вещество

nitrogen oxide - окись азота

particles - частички

mortality rate - смертность

acid rain - кислотный дождь

decline of forests - гибель лесов

long-range - крупномасштабный

vehicle - средство передвижения, автомобиль

contamination - загрязнение, заражение

emission - выброс загрязняющих веществ в атмосферу

fine suspended particulate matter - мельчайшие взвешенные в воздухе частички

major pollution events - случаи сильного загрязнения воздуха

soot - сажа

Compiled by Elena Lamanova