Which of the following is not a cause of natural pollution ?

Options

A. Volcanic eruption
B. UV radiation
C. Forest fire
D. Mercury

Explanation

To determine which of the following is not a cause of natural pollution, we can analyze each option provided:

1. **Volcanic Eruption**: Volcanic eruptions release ash, gases, and other pollutants into the atmosphere, contributing to natural pollution. This is a natural phenomenon.

2. **UV Radiation**: Ultraviolet (UV) radiation is a natural part of sunlight that reaches the Earth's surface. While it can cause harm to living organisms, it is not a pollutant in the traditional sense and is a natural occurrence.

3. **Forest Fire**: Forest fires can occur naturally due to lightning strikes or other natural causes. They release smoke and particulates into the air, contributing to natural pollution.

4. **Mercury**: Mercury is a heavy metal that can be found in the environment, but its significant presence in ecosystems is primarily due to industrial activities, such as mining and waste disposal. It is not a naturally occurring pollutant in the same way as the other options.

Based on this analysis, the option that is not a cause of natural pollution is **Mercury**.

### Step-by-Step Solution:
1. **Identify the Options**: Read the four options given: Volcanic Eruption, UV Radiation, Forest Fire, and Mercury.
2. **Analyze Each Option**:
- **Volcanic Eruption**: Recognized as a natural source of pollution.
- **UV Radiation**: A natural occurrence, not classified as pollution.
- **Forest Fire**: A natural event contributing to pollution.
- **Mercury**: Primarily associated with industrial pollution.
3. **Determine the Correct Answer**: Conclude that Mercury is the only option that is not a cause of natural pollution.

### Final Answer:
The correct answer is **Mercury** (Option D).