Nitrogen photoreduction on desert sands under sterile conditions.

Sands from various geographic locations reduce N(2) from the air to NH(3) and traces of N(2)H(4) on exposure to sunlight. This N(2) photofixation occurs under sterile conditions on the surface of finely dispersed titanium minerals such as rutile, utilizing reducing equivalents generated through the photolysis of chemisorbed H(2)O. Abiological N(2) photofixation is suggested to be part of the nitrogen cycle in arid and semiarid regions. It is estimated that about 10 x 10(5) tons of N(2) is photoreduced on the total surface of the earth's deserts per year.