Chair's comments: the nitrogen cycle

摘要

In contrast to general belief, the largest nitrogen pool on our planet is not in the atmosphere (4 X 10~(15) tons) but in the primary rocks (1.9 X 10~(17) tons). Compared to these pools, the N_2 dissolved in the sea is only around 2.2 X 10~(13) tons.The other nitrogen pools (of nitrate, ammonia, organic nitrogen in the soil and in the sea and the nitrogen fixed in plants and animals) are in the order of 2 X 10~(12) tons. Compared to the pools of N_2, this is a tiny fraction. However, these pools are by four orders of magnitude larger, compared to N_2, fixed annually by organisms in the soil and in the sea, which is in the range of 200 to 300 million tons per year (Burns, Hardy 1975).