Comparison of Artificial and Natural Nitrogen Fixation

The process of artifical fixation of nitrogen (chiefly the Haber -Bosch Process) began in 1913, but it did not exceed natural nitrogen fixation rates (ca. 100 teragrams[1011gr]/yr) until about 1970 (Kaiser, 2001). Other important sources of soluble nitrogen are legume crops and NOx emissions from automobiles.

Haber-Bosch reaction: N2 + 3H2 => 2NH3
(iron catylist, 500 oC, 3000 psi)

The runoff of nitrogen into the Mississippi River increased after 1970. After being washed into the Gulf of Mexico, the nitrogen results in eutrophication and anoxia of bottom waters (McIsaac et al., 2001).

Kaiser J. 2001. The other global pollutant: nitrogen proves tough to curb. Science 294: 1268-1269.

McIsaac G.F., David M.B., Gertner, G.Z., Goolsby D.A. 2001. Nitrate flux in the Mississippi River. Nature 414: 166-167.