Nitrogen returns to the atmosphere through a process called "denitrification." This process is part of the nitrogen cycle and involves the conversion of nitrate (NO3-) to gaseous nitrogen (N2) or nitrous oxide (N2O), both of which are released into the atmosphere. Denitrification is typically carried out by certain types of bacteria in anaerobic conditions (environments lacking oxygen), such as in waterlogged soils or in the sediments of lakes, rivers, and wetlands.
