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📌 The Question:

Why is there a concern about copper smelting plants?

1. They may release lethal quantities of carbon monoxide into the environment.
2. The copper slag can cause the leaching of some heavy metals into the environment.
3. They may release sulphur dioxide as a pollutant.

Select the correct answer using the code given below:

(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

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✅ Correct Answer: (b) 2 and 3 only

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🧠 Classroom Explanation:

Copper smelting is a pyrometallurgical process in which copper is extracted from its ore by applying high temperatures, usually in the presence of oxygen-enriched air.

🔹 Statement 1 – Incorrect
While carbon monoxide (CO) can be produced during incomplete combustion, copper smelting plants are not major sources of lethal CO emissions under normal regulated operations. The major air pollutants of concern are sulphur compounds and particulate matter, not CO as a primary lethal emission.

🔹 Statement 2 – Correct
Copper smelting generates copper slag, which contains heavy metals such as:
• Lead (Pb)
• Cadmium (Cd)
• Arsenic (As)
• Zinc (Zn)
• Nickel (Ni)

Under natural weathering, these metals can leach into soil, surface water, and groundwater, causing long-term environmental contamination.

🔹 Statement 3 – Correct
Copper ores often contain sulphur. During smelting, sulphur is oxidized to sulphur dioxide (SO₂), a major air pollutant that:
• Causes acid rain
• Irritates respiratory systems
• Contributes to smog formation

Hence, statements 2 and 3 are correct.

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🔍 Curiosity Raiser:
Did you know?
👉 The Sterlite Copper Plant controversy in Thoothukudi (Tamil Nadu) became a landmark case highlighting SO₂ emissions, heavy-metal pollution, and community health risks linked to copper smelting.

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📚 Enrich Notes (Prelims Value-Add):

• Copper smelting = major source of SO₂ globally
• Smelter dust often contains toxic trace metals
• Modern plants use acid plants to convert SO₂ into sulphuric acid
• Slag reuse without safeguards can contaminate groundwater

Mnemonic:
👉 “Smelter = SO₂ + Slag + Heavy Metals”

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🪶 IAS Monk Whisper:
When metals are purified by fire, the air and earth silently bear the scars.