University:
High School
Course:
High School Chemistry
Academic year:

2024
Views:

159

Pages:

1
Author:

jongli1s

Nitrogen Cycle: Background Information Nitrogen is an element that is found in both the living and nonliving portions of our planet. Nitrogen moves slowly through the cycle and is stored in places like the atmosphere, living organisms, soils, and oceans. Most of the nitrogen on Earth is in the atmosphere. Approximately 80% of the Earth’s atmosphere is made of nitrogen gas (N2). All plants and animals need nitrogen to make amino acids, proteins and DNA, but the nitrogen in the atmosphere is not in a form that they can use. The molecules of nitrogen in the atmosphere can become usable for living things when:  they are broken apart during lightning strikes or fires  by bacteria  especially bacteria associated with legume (bean) plants Other plants get the nitrogen they need from soil in the form of inorganic nitrate (NO3- ). Nitrogen is a limiting factor for plant growth (if there isn’t enough nitrogen, the plants won’t grow). Animals get the nitrogen they need by consuming plants or other animals that contain organic molecules made partially of nitrogen. When organisms die, their bodies decompose bringing the nitrogen into the soil. As dead plants and animals decompose, nitrogen is converted into inorganic forms such as ammonium salts (NH4+) by a process called mineralization. The ammonium salts are absorbed in the soil and then chemically altered by bacteria into nitrite (NO2) and then nitrate (NO3- ). Nitrate is the form commonly used by plants. After it is dissolved in water, it is returned to the atmosphere by bacteria in a process called denitrification. Certain actions of humans are causing changes to the nitrogen cycle and the amount of nitrogen that is stored in reservoirs. The use of nitrogen-rich fertilizers can cause nutrients to leak into nearby waterways as the fertilizer washes into streams and ponds. This causes plants to grow rapidly until they use up the nitrogen supply and die. The number of herbivores will increase when the plant supply increases and then the herbivores are left without a food source when the plants die. In this way, changes in nutrient supply will affect the entire food chain. Additionally, humans are altering the nitrogen cycle by burning fossil fuels and forests, which releases various solid forms of nitrogen. Farming also affects the nitrogen cycle. The waste associated with livestock farming releases a large amount of nitrogen into soil and water.