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.
In light of the above statements, choose the most appropriate answer from the options given below:

• 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:

Acid sulfate soils are often referred to as "cat clays." Their reclamation requires applying lime ($\text{CaCO}_3$) to neutralize acidity and maintaining a high water table to prevent pyrite oxidation.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Acid sulfate soils contain iron sulfides (primarily pyrite, $\text{FeS}_2$).
When exposed to oxygen due to drainage or excavation, these sulfides oxidize to produce sulfuric acid ($\text{H}_2\text{SO}_4$), which severely lowers soil pH.

Step 2: Detailed Explanation:
- Statement (I) is true: The extreme acidity (pH often $<$ 0) of acid sulfate soils dissolves minerals, releasing toxic concentrations of aluminum ($\text{Al}^{3+}$), iron ($\text{Fe}^{3+}$), and manganese ($\text{Mn}^{2+}$) into the soil solution and surrounding water bodies.
- Statement (II) is false: While some acid sulfate soils contain organic matter, they are highly toxic and unproductive in their natural state due to nutrient deficiencies, aluminum toxicity, and active acid generation.
They require intensive management, such as liming and controlled water tables, to support agricultural crops or diverse plant life.

Step 3: Final Answer:
Statement I is true, and Statement II is false.