Acid Rain

Rain is indespensible for life on Earth.Unpolluted rain is normally slightly acidic, with a pH of 5.6. Carbon dioxide (CO₂) from the atmosphere dissolves   in water to form carbonic acid.

However , pollutants  like sulfur and nitrogen oxides   combine  with the rain, the acidity of rain  increases greatly. These gases are oxidized in the air before been  captured by raindrops to form nitric and sulfuric acids  .  We commonly know this as acid rain, but we can have acidic snow or hail and even acidic dust particles falling from the sky.

  

Acid rain is a human-related phenomena. Since our industries are so fond of burning fossil fuels (coal and oil) they tend to release a lot of sulfur into the air. This sulfur combines with the oxygen already present in the air to form sulfur dioxide (SO₂).

Also, since we like to drive big fancy cars rather than ride bikes or walk, we cause the formation of nitrogen oxides (NO or NO₂ or NO ₃, etc) in air from burning gasoline.

CHEMICAL REACTIONS:

Formation of SO₂ and nitrogen oxides (NO & NO_x):

S(in fuel) + O₂ -------> SO₂
N₂ + O₂ -------> 2NO
NO + .5O₂ -----> NO₂
Formation of hydrogen peroxide

VOC + sunlight + HO₂ (in air) -------> H₂O₂
***VOC = Volatile Organic Compound ***
Formation of acids :

SO₂ + H₂O₂ and O₃ (in clouds) -------> H₂SO₄ SO₂+ OH + O₂ (in air) --------------> H₂SO₄
SO₂ + Oxidants (from wet surfaces) --> H₂SO₄ 
NO_x + sunlight + OH (air) ------------> HNO₃

EFFECTS OF ACID RAIN

 

 
 The acids can cause a lot of harm to things that we care about and enjoy. For example. some animals, like frogs and fish, have difficult time adapting to and reproducing in an acidic environment.

 Also, the leaves of many plants and trees can be severely damaged by acidic precipitation. It is believed that acid rain leaches calcium and magnesium from the soil. This causes a decrease in  the ratio of calcium to aluminum in the soil, which stimulates the uptake of aluminum by roots. The uptake of aluminum by trees and plants can be destructive. Finally, in cites and towns all over the world, stone structures, such as buildings, ancient ruins, etc are being deteriorated by the corrosive effects of acidic rainfall.