Acid rain

   

   A rain with pH of about 5.2 or below due to the presence of sulphur dioxide and nitrogen oxides as a result of combustion of fossil fuels.

    The term acid rain was coined by Scottish chemist Robert Angus ( father of acid rain) in 1852. His findings were published in :

Air and rain: The beginnings of a Chemical Climatology , 1872.

According to EPA ( Environmental Protection Agency) sulphur dioxide and nitrogen oxides released from thermal power plants , vehicles and oil refineries, volcanic activities, forest fire and bacterial decomposition of the organic matters are the main cause of acid rain. In the above reactions formation of these acids  in the atmosphere are described. Acid rain contains sulfuric acids or nitric acid and these may in any form of precipitation or dust, gases, snow,fog ,hail,etc.So, it may be of wet deposition or dry deposition. Normal pH of rain or ordinary water is around 5.6 because of the presence of carbonic acid,  a result of the reaction between carbon dioxide and water.

  Sulphuric acid contributes 60-65% to the acid rainand Nitric acid contributes 30-35% .

Effect of acid rain on plants: 

     Acid rain leaches aluminium from the soil; this aluminium is harmful to the plants. Acid rain washes the cuticle of leaves , as a result plant growth stunts.

Effect on aquatic flora and fauna:

    The pH of a healthy lake is 6.5> .If the pH of a lake is below 5, then fish tends to die. If it is of 4, then the lake is declared as dead.

 Effect on crops: 

    Acid rain makes the fertile top soil acidic, as a result of this quality of soil and ecology of soil microbes has been changed. Hence, the fertility of the soil decreases and  production of crop reduced.

Stone leprosy/ stone cancer: 

     Sulphur dioxide, nitrogen oxides and carbon particles emmited from Mathura Oil Refinery, tannery chimneys and vehicles weathered and eroded the white fecade of the Tajmahal day by day and turned it yellow.To control it "the Taj  Trapezium Zone" i.e., 10,400 sq kilometres has been established. Multani Mitti or Fuller's earth is also applied on the Tajmahal to make it lustrous.

    Victoria Memorial Hall, Kolkata and  British Parliament House are also suffering from this  stone cancer.

Solution:

 (1) Use of renewable energy like solar energy and wind power in place of fossil fuels.

(2) Vehicles combustion technology must be improved.

(3) New devices should be introduced in the power plants, refineries and furnaces.

       MCQ

Q1. What pH is required for aquatic animals and plants to survive?

(a) 7

(b) 7.5

(c) 4.8 ( ans)

(d) 6.5

Q2. Who coined the term acid rain?

(a) Christ Ralph

(b) Elmer Joseph Clark

(c) Ernst Flower

(d) Robert Angus Smith (ans)

Q3. The main contributors of acid rain are

(a) Oxides of sulphur and carbon

(b) Oxides of sulphur and nitrogen (ans)

(c) Carbon dioxide and carbon monoxide 

(d) Oxides of nitrogen and carbon 

Q4. Acid rain is a kind of 

(a) Air pollution (ans)

(b) Water pollution 

(c) Soil pollution 

(d) None of the above

Q5. Acid rain damages

(a) Sculptures of marble 

(b) Flora and fauna 

(c) Crop production 

(d) All of the above (ans)

Q6. Acid rain reacts with marble and limestone to form

(a) Calcium carbonate 

(b) Calcium hydroxide 

(c) Calcium sulphate (ans)

(d) None of the above 

Q7. Which of the following is responsible for Yellowstone in Tajmahal?

(a) Organic carbon

(b) Black carbon

(c) Brown carbon 

(d) All of the above (ans)