Correct Option
The burning of crop or biomass residue releases a complex mixture of gases and particulate matter into the atmosphere. These include:
- Carbon monoxide (CO): This gas is a product of incomplete combustion of organic matter.
- Methane (CH₄): It is released, particularly under low-oxygen burning conditions, during biomass combustion.
- Sulphur dioxide (SO₂): Its emission occurs when biomass containing sulphur compounds is burned.
- Ozone (O₃): While not directly emitted, ozone is a secondary pollutant. It forms in the lower atmosphere through photochemical reactions involving precursor gases such as methane (CH₄) and other volatile organic compounds (VOCs), along with nitrogen oxides (NOx), which are released during biomass burning, in the presence of sunlight. Therefore, ozone formation is indirectly linked to biomass burning emissions.
Thus, all four substances are associated with the atmospheric impact of burning crop/biomass residue, either through direct emission or secondary formation.
Incorrect Options
Options (a), (b), and (c) are incorrect as they do not include all the substances (Carbon monoxide, Methane, Ozone, and Sulphur dioxide) that are released or formed in the atmosphere due to the burning of crop/biomass residue.