What is the process called that converts nitrites and nitrates into free nitrogen?

The process that converts nitrites and nitrates into free nitrogen is called denitrification. This biological process is carried out by certain bacteria found in oxygen-depleted environments, such as wetlands and waterlogged soils. During denitrification, these bacteria use nitrites and nitrates as oxygen sources instead of molecular oxygen, reducing these compounds to nitrogen gas (N2) or, in some cases, nitrous oxide (N2O), which is then released into the atmosphere.

Denitrification is crucial for the nitrogen cycle because it helps maintain the balance of nitrogen in ecosystems. By removing excess nitrates and nitrites from the soil, it prevents issues such as water pollution and eutrophication, which can happen when these compounds accumulate in water bodies.

The other processes listed are important components of the nitrogen cycle but serve different functions. Nitrification, for instance, is the process that converts ammonia into nitrites and then nitrates, while ammonification is the conversion of organic nitrogen from dead organisms into ammonia. Decomposition involves the breakdown of dead organic matter, which can include the release of nitrogen compounds but does not specifically refer to the transformation of nitrates or nitrites into nitrogen gas.