When atmosphere become polluted

Options

A. When `CO_2` value is `0.03%` in atmosphere
B. WhenB.O.D. value is 5 ppm
C. Due to presence of Eutrophication
D. If concentration of dissolved oxygen of water is greater than 6 ppm

Answer

To determine when the atmosphere becomes polluted, we need to analyze the provided options one by one.

### Step-by-Step Solution:

1. **Evaluate Option 1: CO2 value of 0.03%**
- The first option states that the atmosphere becomes polluted when the CO2 concentration is 0.03%.
- However, the normal atmospheric CO2 level is around 0.04%. Therefore, a CO2 concentration of 0.03% does not indicate pollution.
- **Conclusion**: This option is incorrect.

2. **Evaluate Option 2: BOD value of 5 ppm**
- The second option refers to the Biochemical Oxygen Demand (BOD) value being 5 ppm.
- A BOD value of 5 to 6 ppm is typical for clean water. Values above this indicate increasing levels of organic pollution.
- Since 5 ppm is considered clean, this option does not indicate pollution.
- **Conclusion**: This option is also incorrect.

3. **Evaluate Option 3: Presence of Eutrophication**
- The third option discusses eutrophication, which is the enrichment of water bodies with nutrients (like nitrogen and phosphorus).
- This process can lead to excessive growth of algae, which depletes oxygen in the water and disrupts aquatic ecosystems.
- The disturbance caused by eutrophication can lead to a loss of biodiversity and is considered a form of pollution.
- **Conclusion**: This option is correct.

4. **Evaluate Option 4: Concentration of dissolved oxygen greater than 6 ppm**
- The fourth option states that if the concentration of dissolved oxygen in water is greater than 6 ppm, it is not polluted.
- In fact, a dissolved oxygen level below 6 ppm can inhibit fish growth, but this does not directly indicate atmospheric pollution.
- **Conclusion**: This option is incorrect.

### Final Conclusion:
The atmosphere becomes polluted due to the process of eutrophication, as indicated by option 3.