Match List-I (Pollution Index / Tool) with List-II (Purpose) and select the correct code:

Question

Match List-I (Pollution Index / Tool) with List-II (Purpose) and select the correct code:

List-I

i. AQI

ii. WQI

iii. BOD

iv. PSI

List-II

a. Organic pollution in water

b. Overall water quality

c. Urban air quality

d. Old US index

Choose the correct match:

1. A. i-c, ii-b, iii-a, iv-d (Correct answer)
2. B. i-b, ii-c, iii-d, iv-a
3. C. i-d, ii-a, iii-c, iv-b
4. D. i-c, ii-a, iii-b, iv-d

Correct Answer

Option A — i-c, ii-b, iii-a, iv-d

Detailed Solution & Explanation

The correct answer is i-c, ii-b, iii-a, iv-d.

Key Points

• Each index or parameter answers a different question:
  • i. AQI - c. Urban air quality. A composite index converting pollutant concentrations into one number and colour band.
  • ii. WQI - b. Overall water quality. The Water Quality Index aggregates several parameters — pH, dissolved oxygen, turbidity, coliforms — into a single rating.
  • iii. BOD - a. Organic pollution in water. Biochemical Oxygen Demand measures the oxygen microbes consume degrading organic matter, so it is a measure of organic load rather than an index.
  • iv. PSI - d. Old US index. The Pollutant Standards Index, the United States' earlier air index.

Additional Information

• BOD is the odd one out by nature: AQI, WQI and PSI are composite indices, while BOD is a directly measured parameter that feeds into an index. Spotting that resolves the question before the pairings are examined.
• The standard test is BOD₅ at 20°C — the oxygen consumed over five days of incubation. Untreated domestic sewage typically runs 200-300 mg/L, and the Indian discharge standard for treated sewage into inland surface water is 30 mg/L.
• COD exceeds BOD for the same sample because chemical oxidation attacks both biodegradable and non-biodegradable matter, whereas BOD counts only what microbes can digest.
• India's NAQI replaced an older, simpler index in 2014; PSI's presence in this question is purely as a historical distractor.