What is the primary cause of ocean acidification?
- ASulfur dioxide (SO₂ ) emissions from industrial factories cause acid rain over the oceans
- BAgricultural runoff release nitric acid into oceans
- CIncreased carbon dioxide (CO₂ ) is absorbed by seawaterCorrect
- DPlastic waste in the oceans breaks down into microplastics
Solution
Concept
The oceans absorb extra atmospheric CO₂. It forms carbonic acid in seawater and lowers pH.
Formula
CO2 + H2O ⇌ H2CO3 ⇌ H^+ + HCO3^-
Step-by-step solution
1. The ocean absorbs about a quarter of the CO₂ released by human activity. 2. CO₂ reacts with water to form carbonic acid (H₂CO₃). 3. Carbonic acid releases H⁺ ions, so seawater pH falls. 4. This is ocean acidification, so the primary cause is more CO₂ absorbed by seawater.
Explanation
More CO₂ in the air dissolves in seawater and forms carbonic acid. This lowers the pH of the ocean. So the main cause is the absorption of increased CO₂.
Why the other options are wrong
A: SO₂ and acid rain have only a local, minor effect. B: Agricultural runoff causes eutrophication, not the main acidification. D: Microplastics are a pollution problem and do not change ocean pH much.
Shortcut
Ocean acidification = CO₂ dissolving in sea water.
Common mistake
Choosing acid rain (SO₂) because it sounds like acid.
Correct answer: C) Increased carbon dioxide (CO₂ ) is absorbed by seawater