Acid Rain and Ocean Acidification Notes

Acid Rain and Acid Deposition

• Mechanism of Acid Deposition:
  • When fossil fuels containing sulfur are burned, sulfur dioxide ($SO_2$) and nitrogen oxides ($NO_x$) are released into the atmosphere.
  • In the atmosphere, these chemical compounds combine with water ($H_2O$) to form acids.
  • Carbon dioxide ($CO_2$) also reacts with water to yield carbonic acid ($H_2CO_3$):

$CO_2 + H_2O \rightarrow H_2CO_3$

• Environmental Effects of Acidic Precipitation:
  • Atmospheric moisture falls to the ground with a low pH as acidic precipitation, including acid rain and acid snow.
  • Acidic precipitation lowers the overall pH of terrestrial and aquatic ecosystems.
  • It negatively impacts multiple components of the ecosystem, including animals, plants, and soil health.

Ocean Acidification

• Impact on Shell-Building Marine Organisms:

  • Acid precipitation and atmospheric absorption lead directly to the acidification of ocean waters.
  • Many marine creatures possess shells or exoskeletons composed of calcium carbonate ($CaCO_3$).
  • Ocean acid reacts directly with calcium carbonate ($CaCO_3$) and dissolves it, effectively eating away at the bodies and structural defenses of these organisms.

• Role of the Ocean as a Carbon Sink:

  • The ocean functions as a massive carbon sink that absorbs atmospheric gases.
  • As human activity generates excess amounts of carbon dioxide ($CO_2$), the oceans absorb increasingly large quantities of $CO_2$.
  • Consequently, ocean waters are steadily becoming more acidic as they continue to take on excess carbon dioxide.

Remediation and Mitigation Strategies

• Natural Soil Buffering:
  • Sedimentary rocks present in the soil, such as limestone ($CaCO_3$), help lessen the harmful impacts of acid deposition.
  • Limestone acts as a natural chemical buffer that neutralizes acidic deposition before it can lower ecosystem pH further.