Question

Given below are two statements:
Statement (I): Acid sulfate soils can release harmful concentrations of heavy metals such as aluminum, iron, and manganese into the environment under acidic conditions.
Statement (II): Acid sulfate soils are typically characterized by their high organic matter content, which contributes to their fertility and ability to support diverse plant life.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

Remember: Acid sulfate soils are chemically active under acidic conditions and can release toxic elements.

Answer 1

The Correct Option is C

Acid sulfate soils can indeed release harmful levels of heavy metals under acidic conditions, affecting ecosystems. However, these soils are not typically rich in organic matter, contradicting Statement (II).

Answer 2

Mechanism-based check: Acid sulfate soils form when sulfide minerals such as pyrite (\( \text{FeS}_2 \)) are exposed to air and oxidise, generating sulfuric acid and driving soil pH down to strongly acidic levels.
This acidity dissolves aluminium, iron, and manganese oxides and silicates, releasing them as soluble, often toxic ions into soil water and drainage, which directly supports Statement I.
These soils typically form in waterlogged coastal and estuarine sediments and their extreme acidity and metal toxicity generally suppress rather than support plant growth, so the claim that they are inherently fertile due to high organic matter, Statement II, does not hold.