Unseen Plague

Another Environmental Problem, the Acid Rain, known as well "The Unseen Plague".

The Culprits: Nitrogen Oxides and Sulphur Dioxide.


pH scale:
This scale goes from 0 ( most Acidic) to 14 (most Alkaline). A pH value of 7 is neutral, which means that it is neither acidic nor alkaline.

Rain is always slightly acidic because it mixes with naturally occurring oxides in the air. Unpolluted rain would have a pH value of between 5 and 6. When the air becomes more polluted with nitrogen oxides and sulphur dioxide the acidity can increase to a pH value of 4. Some rain has even been recorded as being pH2.

Primary sources of emission:
1. Natural Phenomena: Volcanic eruption & Biological processes producing
Methyl Sulfide
2. Human Activity: Burning of Fossil Fuel, COAL in particular.


Adverse Effects of Acid Rain on Forest & Trees:

• Dissolve and wash away the nutrients and minerals in the soil which help the trees to grow.
• Cause the release of harmful substances such as aluminum into the soil.
• wear away the waxy protective coating of leaves, damaging them and preventing them from being able to photosynthesize properly.
• A combination of these effects weakens the trees which means that they can be more easily attacked by diseases and insects or injured by bad weather.
  

Adverse Effects of Acid Rain on Aquatic Life:

• Acid rain runs off the land and ends up in streams, lakes and marshes.
• The acidity of the water can cause deformity in young fish and can prevent eggs from hatching properly.
• The acidity of the water causes toxic substances like aluminum to be released into the water from the soil, harming fish and other aquatic animals.
• Whole aquatic ecosystem can be disrupted. Many different species of plants and animals all are depending on one another to survive. If a species of fish disappears, the animals which feed on it will gradually disappear too. If the extinct fish used to feed on a particular species of large insect, that insect population will start to grow, this in turn will affect the smaller insects or plankton on which the larger insect feeds.
  

Adverse Effect on Building or Structure:

• Acid Rain is corrosive.
• Statues, buildings, vehicles, pipes and cables can all suffer. The worst affected are things made from limestone or sandstone as these types of rock are particularly susceptible and can be affected by air pollution in gaseous form as well as by acid rain.

Technical Solutions:

1. Flue Gas Desulphurization (FGD)

Sulphur can be 'washed' out of smoke by spraying a mixture of water and powdered limestone into the smokestack.

As a result of stringent environmental protection regulations regarding SO₂ emissions that have been enacted in a great many countries, SO₂ is now being removed from flue gases by a variety of methods:

• Wet Scrubbing using a slurry sorbent, usually limestone or lime, to scrub the gases.
• Spray-dry scrubbing using similar sorbent slurries.
  
• Dry sorbent injection systems.

For a typical coal-fired power station, FGD will remove 95 percent or more of the SO₂ in the flue gases.


2. Automobile Emission Control

Tailpipe emissions control can be categorised into three parts:

1. Increasing engine efficiency
2. Increasing vehicle efficiency
3. Cleaning up the emissions-->the Catalytic Converter.
   

General Techniques:

1. Promote alternative sources of energy, Hydroelectric, Solar, Wind...etc.
   
2. Conserve energy--Car Pooling, Public Transportation, Efficient Energy Strategics,
   

Experts say that if energy was used more carefully, we could cut the amount of fuel burned in half! When less energy is used, less coal is burnt, and as a result, there is less acid rain.