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?

1. Coal ash contains arsenic, lead and mercury. — Correct. Coal ash is known to contain toxic trace heavy metals such as arsenic, lead and mercury.

2. Coal-fired power plants release sulphur dioxide and oxides of nitrogen into the environment. — Correct. Burning coal emits major air pollutants including SO2 and NOx.

3. High ash content is observed in Indian coal. — Correct. Indian coal generally has high ash content compared to many imported coals.

Therefore, all three statements are correct.