Question

what are the five causes of air pollution?...and prevention

Answer 1

Methods of controlling gaseous pollutants-The air pollution caused by gaseous pollutants like hydrocarbons, sulphur dioxide, ammonia, carbon monoxide, etc can be controlled by using three different methods-Combustion, Absorption and Adsorption.Combustion-This technique is applied when the pollutants are organic gases or vapours. The organic air pollutants are subjected to 'flame combustion or catalytic combustion' when they are converted to less harmful product carbon dioxide and a harmless product water.Absorption-In this method, the polluted air containing gaseous pollutants is passed through a scrubber containing a suitable liquid absorbent. The liquid absorbs the harmful gaseous pollutants present in air.Adsorption-In this method, the polluted air is passed through porous solid adsorbents kept in suitable containers. The gaseous pollutants are adsorbed at the surface of the porous solid and clean air passes through.Methods of controlling particulate emissions-The air pollution caused by particulate matter like dust, soot, ash, etc can be controlled by using fabric filters, wet scrubbers, electrostatic precipitators and certain mechanical devices.Mechanical Devices-It works on the basis of following:Gravity-In this process, the particulate settle down by the action of gravitational force and get removed.Sudden change in the direction of air flow-It brings about separation of particles due to greater momentum.

2. Fabric Filters-The particulate matter is passed through a porous medium made of woven or filled fabrics.

The particulate present in the polluted air are filtered and gets collected in the fabric filters, while the gases are discharged.The process of controlling air pollution by using fabric filters is called 'bag filtration'.

3. Wet Scrubbers-They are used to trap SO2, NH3 and metal fumes by passing the fumes through water.

4. Electrostatic Precipitators-When the polluted air containing particulate pollutants is passed through an electrostatic precipitator, it induces electric charge on the particles and then the aerosol particles get precipitated on the electrodes.

Some other methods of controlling Air Pollution:

Tall chimneys should be installed in factories.Better designed equipment and smokeless fuels should be used in homes and industries.Renewable and non-polluting sources of energy like solar energy, wind energy, etc should be used.Automobiles should be properly maintained and adhere to emission control standards.More trees should be planted along roadsides and houses.