Assertion (A): Acid rain can threaten aquatic life in rivers and lakes. Reason (R): Acid rain lowers the pH of river water below the survival range…

Correct Option

The correct option is Both A and R are true and R is the correct explanation of A.

Explanation

Acid rain is precipitation with a pH value of less than 5.6. It is formed when oxides of sulfur and nitrogen in the atmosphere react with moisture to produce sulfuric acid and nitric acid. This acidic precipitation significantly impacts the chemistry of soil and water bodies.

Statement-wise Analysis

• Assertion (A): Correct. Acid rain poses a severe threat to aquatic ecosystems. When acid rain flows into rivers and lakes, it alters the water chemistry, making the environment hostile for various forms of aquatic life, including fish, insects, and aquatic plants.
• Reason (R): Correct. The specific mechanism causing harm to aquatic life is the reduction in the pH level of the water. Most aquatic organisms require a near-neutral pH (typically between 6.5 and 8.5) for optimal physiological function. Acid rain lowers the pH of these water bodies below the survival range (often below pH 5.0), leading to reproductive failure, physiological stress, and death.

Justification for

Both A and R are true and R is the correct explanation of A

: The Assertion identifies the ecological impact (threat to aquatic life), and the Reason identifies the chemical cause (lowering of pH) that directly results in that impact. Thus, R is the correct explanation for A.

Key Takeaway: Acid rain acidifies water bodies by lowering the pH below 5.6, creating toxic conditions that disrupt the biological balance and survival of aquatic organisms.