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. Statement 1 is correct. Coal ash, the residue from burning coal, contains various trace elements present in the original coal seam, including heavy metals like arsenic, lead, and mercury. The concentration varies depending on the coal source. 2. Statement 2 is correct. Combustion of coal in power plants releases several pollutants into the environment. Sulphur dioxide (SO2) is formed from sulphur in the coal, and oxides of nitrogen (NOx) are formed due to high temperatures reacting nitrogen in the air and coal. 3. Statement 3 is correct. Indian coal, particularly the Gondwana coal that constitutes the majority of reserves, is generally characterized by high ash content (often exceeding 30-40%) and low calorific value compared to coals found in many other countries. 4. Therefore, all three statements are correct.