Acid Deposition
What is acid deposition?
- Rain is naturally acidic because of dissolved CO2 which forms carbonic acid
H2O (l) + CO2 (g) ⇌ H2CO3 (aq)
- Carbonic acid is a weak acid and dissociates in the following equilibrium reaction giving a pH of 5.6
H2CO3 (aq) ⇌ H+ (aq) + HCO3- (aq)
- For that reason acid rain is defined as rain with a pH of below 5.6
- Acid deposition includes all processes by which acidic components leave the atmosphere
- This could be gases or precipitates
- There are two types of deposition: wet acid deposition and dry acid deposition
- Wet acid deposition refers to rain, snow, sleet, hail, fog, mist and dew
- Dry acid deposition refers to acidic particles and gases that fall to the ground as dust and smoke
- Acid deposition is formed when nitrogen or sulfur oxides dissolve in water to form HNO3, HNO2, H2SO4 and H2SO3