Ward B B
Marine Sciences Department, University of California, Santa Cruz 95064, USA.
Life Support Biosph Sci. 1996;3(1-2):25-9.
Nitrification is an essential step in the nitrogen cycle of natural systems because it links organic matter degradation to fixed nitrogen loss. Ammonium released by ammonification is oxidized to nitrate by nitrification, and can then be reduced to dinitrogen gas by denitrification, resulting in net loss of fixed nitrogen from the system. Whether organic matter degradation results in net ammonium release depends largely on the quality of the organic substrate and interactions among members of the microbial community involved in nitrogen and organic matter cycling. In sediments, nitrogen cycle processes depend on the supply of organic matter and oxygen from overlying water. The nature of the net flux (which direction and which form of nitrogen) is a function of closely coupled reactions (ammonification-nitrification-denitrification) in the nitrogen cycle.
硝化作用是自然系统氮循环中的一个关键步骤，因为它将有机物降解与固定氮损失联系起来。氨化作用释放的铵通过硝化作用被氧化为硝酸盐，然后通过反硝化作用被还原为氮气，导致系统中固定氮的净损失。有机物降解是否导致铵的净释放很大程度上取决于有机底物的质量以及参与氮和有机物循环的微生物群落成员之间的相互作用。在沉积物中，氮循环过程取决于上覆水中有机物和氧气的供应。净通量的性质（氮的方向和形式）是氮循环中紧密耦合反应（氨化作用-硝化作用-反硝化作用）的函数。
