Question

1. what is denitrification?
2. how do human activities affect the nitrogen cycle? give two examples.

Explanation:

Denitrification is a process in the nitrogen cycle where nitrate (\(NO_{3}^{-}\)) is reduced to nitrogen gas (\(N_{2}\)) by denitrifying bacteria. This occurs under anaerobic (low - oxygen) conditions.

For human activities affecting the nitrogen cycle:

• Fertilizer use: Excessive use of nitrogen - based fertilizers in agriculture leads to an increase in nitrate levels in soil and water. Some of this nitrate can leach into groundwater or run off into surface waters, causing eutrophication (excessive growth of algae due to nutrient enrichment).
• Combustion of fossil fuels: Burning fossil fuels releases nitrogen oxides (\(NO_{x}\)) into the atmosphere. These can contribute to acid rain (when they react with water vapor, oxygen, and other chemicals to form nitric acid) and also affect the nitrogen balance in ecosystems as they can be deposited back on land or water.

Answer:

1. Denitrification is the process where nitrate (\(NO_{3}^{-}\)) is reduced to nitrogen gas (\(N_{2}\)) by denitrifying bacteria under anaerobic conditions.
2. - Fertilizer use: Increases nitrate levels, can cause eutrophication. - Combustion of fossil fuels: Releases \(NO_{x}\), contributes to acid rain and disrupts nitrogen balance.