**Introduction:**
Particulate matter (PM) refers to a mixture of solid particles and liquid droplets found in the air. These particles can vary in size and composition. Air pollution often contains high concentrations of PM, which can have detrimental effects on human health and the environment. In polluted air, the presence of PM can catalyze chemical reactions, including the oxidation of sulfur dioxide (SO2).

**Explanation:**
When sulfur dioxide (SO2) reacts with oxygen (O2) in the presence of particulate matter, it undergoes oxidation to form sulfur trioxide (SO3). This reaction is catalyzed by the particulate matter, which provides a surface for the reaction to occur.

The overall reaction can be represented as follows:
2SO2 + O2 → 2SO3

**Role of Particulate Matter:**
Particulate matter acts as a catalyst in this reaction by providing a surface for the reaction to take place. The PM particles have a large surface area, which allows for more contact between the reactants and increases the chances of a successful reaction.

**Catalytic Activity:**
The catalytic activity of particulate matter in this reaction is due to its surface properties. PM particles can act as heterogeneous catalysts, meaning they can facilitate a reaction between two or more substances while remaining unchanged themselves. The surface of the PM particles provides an active site where the reactants can adsorb and react.

**Oxidation of Sulfur Dioxide:**
In the presence of particulate matter, sulfur dioxide (SO2) is oxidized to sulfur trioxide (SO3). The reaction involves the transfer of oxygen atoms from the O2 molecule to the sulfur atom in SO2.

**Importance of Oxidation:**
The oxidation of sulfur dioxide to sulfur trioxide is an important step in atmospheric chemistry. Sulfur trioxide can further react with water vapor in the atmosphere to form sulfuric acid (H2SO4), which is a major component of acid rain. Acid rain can have detrimental effects on ecosystems, including damage to vegetation, aquatic life, and infrastructure.

**Conclusion:**
In polluted air, the presence of particulate matter catalyzes the oxidation of sulfur dioxide to sulfur trioxide. This reaction is important in atmospheric chemistry and contributes to the formation of acid rain. Understanding the role of particulate matter in catalyzing chemical reactions is crucial for addressing air pollution and its environmental impacts.

The particulate matter contains ozone which is formed due to the reaction between oxygen and UV rays thus the ozone react with sulphur dioxide to form sulphur trioxide