Consider the following statements:

1. Coal ash contains arsenic, lead and mercury.

2. Coal-fired power plants release sulphur dioxide and oxides of nitrogen into the environment.

3. High ash content is observed in Indian coal.

Which of the statements given above is/are correct?

The correct option is 1, 2 and 3.

Let us analyze each statement step-by-step to understand why they are all correct:

Statement 1 is correct: Coal ash (also known as fly ash or coal combustion residuals) is the waste product left behind after coal is combusted in power plants. It contains significant amounts of toxic heavy metals and metalloids, including arsenic, lead, mercury, selenium, cadmium, and chromium. These substances can leach into water sources and accumulate in the environment, posing serious health hazards.

Statement 2 is correct: When coal is burned, the chemical components within it undergo combustion. Coal naturally contains sulphur and nitrogen. Combustion reacts these elements with oxygen, thereby releasing sulphur dioxide (SO₂) and various oxides of nitrogen (NO_x, such as nitric oxide and nitrogen dioxide) into the atmosphere. These gases contribute directly to air pollution, smog, and acid rain.

Statement 3 is correct: Indian coal is characterized by its high ash content, which typically ranges from 35% to 45% (and sometimes even higher), compared to the ash content in imported coal which is usually around 10% to 15%. This high ash content is due to the drift origin of Indian coal deposits, where mineral matter became intimately mixed with the organic plant material during coal formation.

Therefore, all three statements (1, 2, and 3) are correct, making 1, 2 and 3 the right answer.