Nitrogen Cycle Part 1
Channel: QuickGlanceVideos QGV Channel
Date: 19/11/2019

The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmosphere, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes.
Nitrogen is one of the primary nutrients critical for the survival of all living organisms. It is a necessary component of many biomolecules, including proteins, DNA, and chlorophyll. Although nitrogen is very abundant in the atmosphere as dinitrogen gas (N2), it is largely inaccessible in this form to most organisms, making nitrogen a scarce resource and often limiting primary productivity in many ecosystems. Only when nitrogen is converted from nitrogen gas into ammonia (NH3) does it become available to primary producers, such as plants.
The main processes in the nitrogen cycle. N2 is reduced to NH3 via biological or industrial nitrogen fixation, providing nitrogen fertilizer for plants. However, of the nitrogen added to fields - most of which is in the form of NH3 and NO3- - only 30-50% is taken up by plants, the remainder being metabolized by soil microbes in processes with detrimental environmental impacts. The first of these processes, nitrification, refers to the biological oxidation of NH3 to NO2- and NO3-, which have low retention in soil and pollute the waterways, leading to downstream eutrophication and ultimately the 'dead zones' (low oxygen zones) in coastal waters, for example the Gulf of Mexico. In a second process, denitrification, NO2- and NO3- undergo step wise reduction to N2O and N2. Significant amounts of the N2O produced in this process escape into the atmosphere, contributing to climate change and ozone destruction.