query: What's the first step of the Nitrogen Cycle?
passage: Nitrogen cycle
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. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmosphere nitrogen,[1] making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems.
passage: Nitrogen cycle
In this biological process, nitrite and ammonia are converted directly into molecular nitrogen (N2) gas. This process makes up a major proportion of nitrogen conversion in the oceans. The balanced formula for this "anammox" chemical reaction is: NH+ 4 + NO− 2 → N2 + 2H2O (Δ<i data-parsoid='{"dsr":[13735,13740,2,2]}'>G° = −357kJ⋅mol−1).[14]