7.7 - Acid Rain

Question 1

Sources of NOx and SO2

Answer 1

• NOx and SO2 are the primary pollutants that cause most acid precipitation

Major sources:
- SO2: coal fired power plants metal factories, vehicles that burn diesel fuel
- NOx: Vehicle emissions, diesel generators coal power plants

Limiting Acid Rain
- Reducing NOx and SO2 emissions reduces acid deposition
- higher CAFe stands
- more public transit
- renewable energy sources
- more efficient electricity use
- Since passsage of Clean Air Act, acid depostion has decreased significantly

Question 2

Formation o f Acid Rain

Answer 2

NO2+O2+H2O -> HNO3
SO2 +O2+H2O -> H2SO4
- Releases Nitrate ion, Hydrogen Ions, sulfate ions, Nitric acid, and sulfiric acid ino the atmosphere (clouds)

• NOx and SO2 react with O2 and H2O in the stmosphere forming nitric and sulfurica cid
• Aulfuric acid and nitric acid dissociate in the presence of water into sulfate and nitrate ions, and hydrogen ions (H+)
• Acid rain water (higher H+ concentration) decreases soil and water pH; can limit tree growth in forests down wind from major SO2 ad NOx sources

Question 3

Environmental effects of Acid Rain

Answer 3

• Acidity =higher H+ ion concentration, lower pH

Soil/Water acidification
- H+ ions displace or leech other prosiive charged nutrients (Ca+2, K+) from soil
- H+ ions also make toxic metals like aluminum and mercury mor soluable in soil and water
- this can slow grwoth or kill plants and animas living in the soil or water

Question 4

Enivonmental Effects of Acid Rain

Answer 4

• Aquatic specieshave different pH tolerances

pH tolerance
- as pH decreases (more acid) outside optimal range for species, population decreases
- when pH leaves range of tolerance, they cannot survive at all due to:
- Aluminum toxicity
- Disrupted bloodosmolatiy (Na+/Cl- balance disrupted at low pH)
- Indicator species can be surveyed and used to determine conditions of an ecosystem (soil, water, etc)

Question 5

Mitigating Acid Rain

Answer 5

• limestone (calcium carbonate) is a natural babse that can neutralise acidic soil/water

Limestone
- calcium carbonate reacts with H+ oins, forming HCO3 and giving off Ca+2
- this neutralizes acidic water/soil, moving it closer to a pH of 7
- Regions with limestone bedrock have some natural buffering of acid rain
- humans can also add crushed limestone to soil/waters to neutralize
- Acidic rain can corrode human structures, especially those made from limestone

Limiting SO2 and NOx
- Decreasing these primary pollutants tht drive acid rain can reduce it
- renwable energy’s sources, decreasing coal combustion
- fluidized bed combustion and lower burning temperature for existing coal power plants
- dry or wet scrubbers