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.

1. Copper smelting involves processing copper ores at high temperatures. This process has several environmental concerns. 2. Statement 1 is generally incorrect. While some carbon monoxide (CO) might be produced due to incomplete combustion if carbonaceous materials are used, the primary gaseous pollutant of concern from copper smelting (especially from sulfide ores) is sulphur dioxide (SO2), not CO in lethal quantities. 3. Statement 2 is correct. Copper slag, a major byproduct of smelting, often contains residual heavy metals (such as arsenic, cadmium, lead, zinc) from the original ore. If not managed properly, leaching of these heavy metals from the slag into the surrounding soil and water can occur, causing significant environmental contamination. 4. Statement 3 is correct. Copper ores, particularly sulfide ores like chalcopyrite (CuFeS2), contain significant amounts of sulfur. During the roasting and smelting processes, this sulfur oxidizes and is released primarily as sulphur dioxide (SO2), a major air pollutant contributing to acid rain and respiratory issues. Therefore, the main concerns are related to heavy metal leaching from slag and SO2 emissions.