4. The nature, source & the effects of acid rain.

Acid rain is rain or any other form of precipitation that is unusually acidic. “Acid rain” is a by-product of modern atmospheric pollution – secondary pollutant. The pH of acid rain is bellow 5.6. Acid rain does not occur as rain; it also occurs as mist, fog, sleet, snow, gas and dry dust particles. It caused by pollution in the air, which comes from burning fossil fuels such as oil and coal. Sulfur dioxide (SO₂), Nitrogen oxide (NO_x) and polycyclic aromatic hydrocarbons (PAH) are some of the main compounds that result from burning fossil fuels. They combine in the air to form a chemical mixture, which eventually returns to earth as acid rain. Chemical reactions:

SO₃ + H₂O → H₂SO₄ NO_x + H₂O → HNO_x

Some of this pollution falls close to where it came from; however, weather systems can also carry some of this pollution more than 2.000 km from its source before it falls back down to earth.

Acid rain is an international problem. For ex, Sweden has suffered badly from acid rain damage: 90% of SO₂ that falls on the country every year comes from other countries.

The acidity of rain can be between 5 and 2, and 1000 times more acidic than is natural. In some of the worst cases, the rain is as acidic as vinegar (pH 2,7), lemon juice (pH 2) and battery acid (pH 1). Rainfall in unpolluted areas has pH ~ 5.6.

Sources of acid rain.

Industries can contribute to acid rain if:

- They burn fossil fuels: for ex, the oil and coal that industries use for energy and heating contributes about 17% of the UK’s sulfur dioxide air emissions.

- They use motor vehicles for goods transportation or other business: the exhaust fumes from motor vehicles produce 45% of the UK’s NO_x air emissions and 30% of its are hydrocarbons.

- They use electricity from power stations, which use fossil fuels; 65% of SO₂ emissions come from power stations.

- They have older style technology: much of this uses fuels with high sulfur and nitrogen contents and does not control emissions as well as newer equipment.

Effects of acid rains

Ecological consequences of acid rain:

- Acid rain damages and kills trees, fish and other wildlife.

- It also affects human health. Aluminum (Al³⁺) in natural waters can cause Alzheimer disease – loss of short-term memory.

- Acidity is not always the direct cause of damage. Acid rain can change soil and water. It dissolves nutrients and toxic heavy metals in the soil, and these are then washed into water of rivers and lakes. As a result of this, the soil lacks nutrients and toxic heavy metals in the soil.

It can no longer continue to support trees; freshwater plant and animal life is very often sensitive to the presence of heavy metals.

- Acid rain corrodes also building stone (limestone and marble), fabrics, and metallic constructions.

5. Sustainable strategies on ozone layer & acid rain problems. International cooperation

Industries can help to prevent further damage to the ozone layer:

4 Rs – Strategies: Replace – Recycle – Reuse – Reinvent

By developing and using alternatives (replacement) to ozone-destroying chemicals in the manufacturing processes. Cardboard can be used instead of foam-blown packaging or alternative foam-blowing agents, which do not contain CFCs or HCFCs, can be used. Water-based substances can be used for cleaning instead of solvents witch contain CFCs or HCFCs.

By recycling the CFCs or HCFCs used in fridges and cooling systems. It is possible to dispose of refrigeration systems safely and to collect and recycle CFCs or HCFCs from them.

By carrying out regular checks for leaks in fridges and cooling systems. It is estimated that leakage and wastage in industrial and commercial use is responsible for 50-75% loss of coolant. There more coolant that is list, the more coolant is used.

By doing a survey of all products used by the company to find out which are manufactured with ozone-destroying chemicals and by adopting a policy of avoiding those that are.

By developing new appliances that run on CFCs.

The Montreal Protocol (MP, 1987) - is an international political agreement about ozone layer protection. The countries that have made the agreement have said they will get rid of CFCs, HCFCs and other ozone-destroying chemicals by 2000.

16 September (from 1995) is the International Day of Ozone Layer Protection.

Prevention measures of acid rain problem.

Industries can help to solve the problem by:

- Improving industrial processes.

Inefficient processes can lose as much as 2/3 of the energy generated by a power station, for ex, resulting in unnecessary emissions.

- Assessing their transport policy and, wherever possible, not using motor vehicles. They could also fit to vehicles catalytic converters, which can reduce nitrogen oxide emissions by 90% and remove hydrocarbons completely.

- Fitting “scrubbing” technology such as fluid gas desulfurisation (FGD) to furnaces and power plants to trap unburnt toxic gases before they reach the atmosphere.

- Using low-sulfur fuel (coal and oil).

- Voluntarily saving energy produced by fossil fuels in the following ways: 1) Properly insulating all buildings. Bad insulation causes energy loss in industries as in houses. 2) Improving product design. For ex, inefficient electrical products use more electricity than necessary. It also consumes more fuel to transport products, which are over-packaged or unnecessarily heavy.

- Improved maintenance. Inefficient vehicles, processes, and machinery lead to increased fuel consumption.

- Avoiding unnecessary business trips and fast driving, which both waste fuel

(See also the topic “Greenhouse effect”)

Short-term solutions:

Stoppage measures to reduce the threat of acid deposition by:

• Installation of smokestack scrubbers

• Combustion of low-sulfur or desulfurized coal

• Using catalytic convertors

• Liming lakes to neutralize acidity

Long-term sustainable solutions:

Preventive actions to reduce habitat destruction, loss of species, urban air pollution, water pollution, environmental ills by using : 1.Fuel efficiency; 2. Renewable fuels; 3. Recycling; 4. Population stabilization; 5. Growth management; 6. Market-based strategies; 7. Corporate and individual actions; 8. Environmental legacy.