The pollutant that contributes to the depletion of the ozone layer is

Analysis

The question asks for the specific pollutant responsible for the depletion of the ozone layer. To answer this, we need to understand the chemical process occurring in the stratosphere and identify which substances interfere with the ozone ($O_3$) cycle.

Concept Explanation

The ozone layer acts as a shield, protecting the Earth from harmful ultraviolet (UV) radiation. The depletion of this layer occurs when certain chemicals reach the stratosphere and react with ozone molecules, breaking them down into oxygen ($O_2$).

• CFCs (Chlorofluorocarbons): These are synthetic compounds containing chlorine, fluorine, and carbon. When they reach the upper atmosphere, UV radiation breaks them down, releasing chlorine atoms. A single chlorine atom can destroy thousands of ozone molecules through a catalytic chain reaction.
• NO2 (Nitrogen dioxide): While it contributes to acid rain and photochemical smog, it is not the primary driver of ozone depletion.
• SO2 (Sulfur dioxide): This is a major contributor to acid rain and air pollution, but it does not deplete the ozone layer.
• CO (Carbon monoxide): This is a toxic gas produced by incomplete combustion. It binds to hemoglobin in the blood, preventing oxygen transport, but it does not affect the ozone layer.

Step-by-Step Solution

1. Identify the mechanism: Ozone depletion is primarily caused by the release of free radicals (like chlorine or bromine) into the stratosphere.
2. Evaluate the options: • CFCs are stable at ground level but decompose in the stratosphere to release chlorine radicals. • The other gases (NO2, SO2, CO) are primarily tropospheric pollutants that affect air quality and climate, but they do not possess the specific chemical property of catalytic ozone destruction in the stratosphere.
3. Conclusion: CFCs are the well-documented culprits behind the "ozone hole."

Exam Tip

When you see questions about Ozone Depletion, always look for CFCs (Chlorofluorocarbons). When you see questions about Acid Rain, look for SO2 or NO2. Remembering this distinction will save you time in the exam hall!