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The magical journey of nitrogen: How does it transform into various forms in nature?
Nitrogen is one of the most important elements on Earth and is essential for the maintenance of life. It exists in various chemical forms in the atmosphere, soil and water, and is transformed in nature through different biological and physical processes. This process is called the nitrogen cycle and plays a vital role in maintaining the health and productivity of ecosystems.
The key processes of the nitrogen cycle include fixation, ammonification, nitrification, and denitrification, which together form a complex and harmonious ecological network.
Main processes of nitrogen
Nitrogen exists in various chemical forms in the environment, including organic nitrogen, ammonium (NH+4), nitrite (NO− sup >2), nitrate (NO−3), etc. Microorganisms play a vital role in these processes, operating by capturing energy or accumulating nitrogen in the required form.
Nitrogen fixation
Nitrogen fixation is the process of converting nitrogen gas (N2) into nitrates and nitrites that can be used by plants. This process can be accomplished through natural processes such as lightning strikes, industrial processes, and biological processes. Atmospheric nitrogen needs to be "fixed" into an absorbable form so that plants can use it. Although approximately 5 to 10 billion kilograms of nitrogen are fixed by lightning strikes each year, most nitrogen fixation is accomplished by free-living or symbiotic bacteria such as rhizobia.
Nitrogen assimilation
Plants can absorb nitrate or ammonium from the soil through their root hairs. When nitrate is absorbed, it will first be reduced to nitrite, then converted into ammonium, and finally synthesized into amino acids, nucleic acids, etc. This process demonstrates the interdependence between the plant and the rhizobia, adding a source of nitrogen to the plant.
Amination
When a plant or animal dies or excretes, the initial form of nitrogen is organic. Bacteria or fungi convert organic nitrogen into ammonium (NH+4), a process called ammonification. This process allows nitrogen to be recycled and reused in the ecosystem.
Nitrification
Nitrification is the process of converting ammonium into nitrates and is primarily responsible for soil bacteria such as Nitrosomonas and Nitrobacter. The conversion of ammonium is critical because ammonia is toxic to plants and affects their growth.
Denitrification
Denitrification is the process of reducing nitrate to nitrogen gas (N2), which is the final step in the nitrogen cycle. This process takes place mainly in anoxic environments, such as soil with stagnant water, and is carried out by bacteria such as Pseudomonas and Paracoccus.
Nitrogen conversion is not only related to the productivity of ecosystems, but also affects our daily lives and human health.
Human Impact
With human industrialization and the expansion of chemical fertilizers and plant agriculture, the nitrogen cycle has undergone significant changes. The burning of fossil fuels, the application of nitrogen fertilizers and the release of wastewater have doubled the amount of available nitrogen diverted, a phenomenon that has negative consequences for the environment and health. The release of nitrogen oxides affects atmospheric chemistry and can lead to acid rain and other environmental problems.
Future challenges
As global warming and ocean acidification intensify, our nitrogen cycle will face more challenges. Global impacts on nitrogen transformation, particularly changes in marine environments, will likely lead to ecosystem degradation. In addition, non-renewable nitrogen resources may cause irreversible damage to the ecological environment if not managed.
What we need to think about is, how can we better manage the nitrogen cycle to ensure human health and the sustainable development of the natural environment?
