Sources of Nitrogen Oxides in the Atmosphere

- Lightning Stroke: Lightning is a natural phenomenon that occurs during thunderstorms. During a lightning strike, the electrical discharge in the atmosphere can produce high temperatures and pressures. These extreme conditions cause the nitrogen and oxygen molecules in the air to react and form nitrogen oxides (NOx), including nitric oxide (NO) and nitrogen dioxide (NO2). These nitrogen oxides are then released into the atmosphere.

- Bacteria Living in Soil: Nitrogen is an essential nutrient for plants, and bacteria play a crucial role in the nitrogen cycle. Certain types of bacteria, known as nitrifying bacteria, convert ammonia (NH3) into nitrite (NO2-) and then into nitrate (NO3-). This process, called nitrification, releases nitrogen oxides as byproducts. Additionally, denitrifying bacteria can convert nitrate back into nitrogen gas, which also leads to the release of nitrogen oxides.

- Reaction of Ultraviolet Radiation with Ozone: In the upper atmosphere, ultraviolet (UV) radiation from the sun interacts with ozone (O3) molecules. This interaction causes the ozone to break down into oxygen (O2) and atomic oxygen (O). The atomic oxygen can then react with nitrogen molecules in the air to form nitrogen oxides. These nitrogen oxides, along with other pollutants, can contribute to the formation of smog and the depletion of ozone in the stratosphere.

Explanation:

The correct answer is option 'B' (1, 2). Both lightning stroke and bacteria living in soil are sources of nitrogen oxides in the atmosphere.

Lightning strokes can release significant amounts of nitrogen oxides into the atmosphere due to the high temperatures and pressures generated during the electrical discharge. This phenomenon is a natural source of nitrogen oxides and contributes to their presence in the atmosphere.

Bacteria living in soil play a vital role in the nitrogen cycle. Nitrifying bacteria convert ammonia into nitrite and then into nitrate, releasing nitrogen oxides as byproducts. Denitrifying bacteria, on the other hand, convert nitrate back into nitrogen gas, also releasing nitrogen oxides. These bacterial processes contribute to the natural cycling of nitrogen in ecosystems and the release of nitrogen oxides into the atmosphere.

The reaction of ultraviolet radiation with ozone (option 3) does not directly add nitrogen oxides into the atmosphere. Instead, this reaction leads to the breakdown of ozone and the subsequent formation of nitrogen oxides as a secondary effect. While UV radiation can indirectly contribute to the presence of nitrogen oxides, it is not a direct source.

In summary, both lightning strokes and bacteria living in soil are sources of nitrogen oxides in the atmosphere, while the reaction of ultraviolet radiation with ozone indirectly leads to the formation of nitrogen oxides. Therefore, the correct answer is option 'B' (1, 2).