Natural Sources of Atmospheric CO

METHANE is produced at the Earth's surface by various processes, chiefly biological in origin. Koyama¹ estimated an annual source of 3 × 10¹⁴ g, with rice paddy fields a major contributor, but did not consider the contribution from natural swamps, and his value for the total source may be low by as much as a factor 3. The data of Bainbridge and Heidt² suggest that they may have observed substantial methane production from the coastal marshes of Louisiana. The important atmospheric sinks for methane are³ These reactions constitute permanent destruction of CH₄. Subsequent chemistry leads to formation of CO and CO₂, and we shall argue that CO is more likely. The source of atmospheric CO due to CH₄ is comparable with, and may be larger than, that associated with the internal combustion engine.