Q. Why is there a concern about copper smelting plants?

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

Select the correct answer using the code given below. (UPSC Prelims 2021)
Answer: 2 and 3 only
Notes: The correct answer is [B] 2 and 3 only. Copper smelting is a process of extracting pure copper from its ore, which involves heating and chemical reduction, leading to specific environmental concerns.

• Copper Slag and Heavy Metals (Statement 2 – Correct): Copper slag is a byproduct of the smelting process. If not managed properly, it can lead to the leaching of heavy metals like arsenic, cadmium, and lead into the soil and groundwater, posing a significant threat to the local ecosystem and human health.
• Sulphur Dioxide Release (Statement 3 – Correct): Most copper ores are sulfur-based (like Chalcopyrite). During smelting, the sulfur in the ore reacts with oxygen to form sulphur dioxide (SO2). If not captured by acid plants, this gas contributes to air pollution and acid rain.
• Carbon Monoxide (Statement 1 – Incorrect): While smelting involves combustion, the primary gas of concern in copper smelting is sulphur dioxide, not "lethal quantities" of carbon monoxide. While trace amounts of CO may be produced, it is not the defining environmental hazard associated specifically with copper smelting plants in the way SO2 and slag leaching are.

In India, the environmental impact of copper plants has been a subject of significant legal and social debate, notably regarding the Sterlite Copper plant in Tuticorin, which centered on concerns over SO2 emissions and groundwater contamination.