氮循环的一个关键组成部分就是——在大气中，将纯净的氮固定为成含氮化合物的形式——这或多或少要完全依赖于生物(闪电仅起一点儿作用)。
One crucial part of this cycle-the fixing of pure nitrogen from the atmosphere into useful nitrogen-containing chemicals-depends more or less entirely on living things (lightning helps a bit).
其中一些气体，如，氮，氧，氩，氖等，作为空气的永久组成成分，总是以固定的比例存在于大气中。
Some of them, such as nitrogen, oxygen, argon, neon, and so on, may be regarded as permanent atmospheric components that remain in fixed proportions to the total gas volume.
其中一些气体，如，氮，氧，氩，氖等，作为空气的永久组成成分，总是以固定的比例存在于大气中。
Some of them, such as nitrogen, oxygen, argon, neon, and so on, may be regarded as permanent atmospheric components that remain in fixed proportions to the total gas volume.
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