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. 2013 Sep 3;3:2579. doi: 10.1038/srep02579

Figure 2. Industrial Nr involved in the major transformation pathways of the global N cycle.

Figure 2

Red arrows represent the pathways of the industrial N cycle; grey arrows represent the pathways dominated by microbial activities; green arrows represent the pathways dominated by plants; blue arrows represent the pathways dominated by atmospheric chemical reactions. Due to the difficulty of determining the N oxidation states of industrial Nr compounds, their vertical positions do not follow the order of N oxidation states from −3 to + 5. Abbreviations: BNF, biological N fixation; Denitri, denitrification; HBNF, Haber-Bosch N fixation; Nitri, nitrification.