Different Types Of Acid Rain

Introduction:

Rain is one of the most essential ingredients for the survival of human and animal life on Earth. Although rain is naturally acidic, it is being increasingly acidified by the presence of pollutants in the environment. The term used to describe this problem is “acid rain” [1] Burning of fossil fuels for industrial and transport sector have led to increase in concentrations of gaseous and particulate pollutants in the atmosphere leading to air pollution. [2] The oxides of Carbon, Sulfur and Nitrogen present in the air combine with the moisture in the air and form sulphuric acid, carbonic acid and nitric acid, respectively. When it rains or snow, these acids are brought to the earth in what is called acid rain. [3]

Acid rain

i. Wet Deposition: Wet deposition refers to acid rain in the for of rain, snow, fog or mist. It occurs whem acid chemicals are blown to areas where weather is wet.[1]

ii. Dry Deposition: Dry deposition refers to acidic gases and particles which are blown to the areas where weather is dry. [4] It can be responsible for 20-60% of total acid deposition. [3]

Components of Acid Rain:

The 3 major components of acid rains are sulfur dioxide/sulfur trioxide, carbon dioxide and nitrogen dioxide. These components are deposited in the form of dry and wet depositions. When these pollutants are dissolved in water during rain it forms various acids.

The chemical reaction that results in the formation of acid rain is as following;

 CO2+H2O → H2CO3 (carbonic acid)

 SO2+H2O → H2SO3 (sulfurous acid)

 NO2+H2O → HNO2 (nitrous acid)+HNO3 (nitric acid)

(4) Countries Range of pH Japan 4.7 Europe 4.1-5.4 China 4.1- 4.9 US north west 5.1 - 5.2 US west- middle west 5.0 - 5.5

Methods: There are two major methods to measure acid rain as supported by EPA as there two types of acid rain; wet deposition acid rain and dry deposition acid rain.

• The National Atmospheric Deposition Program is used to measure wet deposition and its website features maps of rainfall pH and other important precipitation chemistry measurements.

• The Clean Air Status and Trends Network (CASTNET) is the other method that is used to measure dry deposition. Its web site features information about the data it collects, the measuring sites, and the kinds of equipment it uses. [4]

Causes of Acid