Typpikierrossa

Typpikierrossa refers to the nitrogen cycle, a biogeochemical process that circulates nitrogen through the Earth's atmosphere, biosphere, and lithosphere. This vital cycle is essential for life as nitrogen is a key component of amino acids, proteins, and nucleic acids. The cycle can be broadly divided into several stages.

The atmosphere is the largest reservoir of nitrogen, existing primarily as nitrogen gas (N2). However, most organisms cannot directly utilize atmospheric nitrogen. Nitrogen fixation is the process by which atmospheric nitrogen is converted into ammonia (NH3) or other nitrogenous compounds that can be used by living organisms. This fixation can occur through biological means, such as by nitrogen-fixing bacteria found in the soil or in symbiotic relationships with plants, or through abiotic processes like lightning or industrial processes.

Once fixed, nitrogen enters the biosphere through assimilation, where plants absorb ammonia or nitrates from the soil and incorporate them into organic molecules. Animals obtain nitrogen by consuming plants or other animals. Ammonification is the process by which decomposers break down organic nitrogen compounds in dead organisms and waste products, returning nitrogen to the soil as ammonia.

Nitrification is another crucial step, where ammonia is converted into nitrites (NO2-) and then into nitrates (NO3-) by specialized bacteria. Nitrates are readily absorbed by plants. Denitrification is the final stage, where bacteria convert nitrates back into nitrogen gas, which is released into the atmosphere, completing the cycle. Human activities, such as the use of fertilizers and combustion, can significantly impact the rate and balance of the nitrogen cycle, leading to environmental issues like eutrophication.