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.

Copper smelting is a process that extracts copper from its ores, typically sulfide ores. This process has several environmental concerns:

1. They may release lethal quantities of carbon monoxide into the environment: While carbon monoxide (CO) can be a product of incomplete combustion in various industrial processes, the primary gaseous emission concern from copper smelting, especially from sulfide ores, is sulfur dioxide. CO is not a defining primary lethal emission from the main copper smelting process itself. Therefore, this statement is not a primary concern for copper smelting.

2. The copper slag can cause the leaching of some heavy metals into the environment: Copper slag is a glassy, granular, and dense byproduct of the copper smelting process. It often contains significant concentrations of heavy metals such as lead, arsenic, cadmium, and zinc. If not properly managed or disposed of, these heavy metals can leach into the soil and groundwater, leading to environmental contamination and potential health risks. This statement is correct.

3. They may release sulphur dioxide as a pollutant: Copper sulfide ores are roasted and smelted, releasing large quantities of sulfur dioxide (SO2) gas. SO2 is a major air pollutant that contributes to acid rain, respiratory problems, and environmental damage. This is a well-known and significant environmental concern associated with copper smelting. This statement is correct.

Therefore, statements 2 and 3 are correct.