The primary process responsible for the depletion of the ozone layer in the stratosphere involves reactions with chlorofluorocarbons (CFCs). Let's break down the mechanism and explain why this is the correct answer.

Step-by-Step Explanation:

1. Understanding the Ozone Layer: The ozone layer is a region in the Earth's stratosphere that contains a high concentration of ozone (O₃). This layer absorbs the majority of the Sun's harmful ultraviolet (UV) radiation, thus protecting living organisms on Earth.
2. Role of Chlorofluorocarbons (CFCs): CFCs are man-made compounds that were widely used in refrigeration, air conditioning, and aerosol propellants. These compounds are stable and can persist in the atmosphere for long periods.
3. Reaction Mechanism: When CFCs reach the stratosphere, they are broken down by UV radiation, releasing chlorine atoms: \(\text{CFC} + \text{UV light} \rightarrow \text{Cl}\)

This chlorine atom is highly reactive and can catalyze the destruction of ozone molecules in a series of reactions:

• \(\text{Cl} + \text{O}_3 \rightarrow \text{ClO} + \text{O}_2\)
• \(\text{ClO} + \text{O} \rightarrow \text{Cl} + \text{O}_2\)

1. Conclusion: Each chlorine atom can destroy thousands of ozone molecules before it is deactivated, significantly thinning the ozone layer. This is why the reactions involving chlorofluorocarbons are primarily responsible for ozone layer depletion.

Ruling Out Other Options:

• Industrial dust particles in the air: While these can affect air quality, they do not impact the stratospheric ozone layer.
• Urban heat island effect: This is a local climate phenomenon affecting temperatures in urban areas, unrelated to ozone depletion.
• Acid rain due to sulfur emissions: Acid rain results from sulfur and nitrogen emissions and affects ecosystems, but it is not directly related to the depletion of the stratospheric ozone layer.