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Pictorial aspect of acidic rain formation
The term acidic rain was first used by Robert Angus in 1872. Literally it means the presence of excessive acids in rain water or the fall of acids mixed with rain and snow. Nitrogen oxides and sulphur dioxide which are acidic gases dissolve in in the rain water in the atmosphere and make it acidic. Acidic rain in fact is a cocktail of mainly H2SO4 (Sulfuric acid) and HNO3 (Nitric acid) where the ratio of these two may vary depending on the relative quantities of oxides of sulphur and nitrogen emitted. H2SO4 is the major contributor (60-70 percent) to acid precipitation. HNO3 ranks second (with 30-40 percent) and HCL third.
Although the oxides sulfur and nitrogen have been recognized as the main components responsible for acid rain, their relative contributions to acid rain is still not very clear because of the highly complex nature of their transport and complexity involved in their removal from rain water. Once these oxides have fallen, along with rain water, it is difficult to remove them from the environment. These oxides may travel long distances in the atmosphere and during this journey, they may undergo several physical and chemical transformations to products which may also fall with rain. Hence, acid rain which is mainly a man made is a global ecological challenge. Normal rain water is always slight acidic because of the fact that CO2 present in the atmosphere gets dissolved in it, forming carbonic acid (H2CO3). Because of the presences of SO2 and NO2 gases as pollutants in the atmosphere, the pH (a measure of how acidic/basic water is) of the rain water is further lowered, often to as low as 2.4 and this type of precipitation of lower pH is called acidic rain.
Formation of Acidic rain
Acid rain is the one phase of acid deposition which can either be wet or dry. It is the form of snow, dew, fog, frost and mist represent the wet form of deposition while dust particles containing sulphates and nitrates, settled on earth, and constitute dry deposition. However, the wet rain is much more common. Wet acid rain every source of energy that we use be it coal, fuel wood or petroleum products have sulphur...