atmospheric oxygen
jhalper | July 23, 2012You’ve heard of the carbon cycle, maybe even the nitrogen cycle. But have you given much thought lately to the sulfur cycle? New research in last week’s Science suggests that we should be paying a bit more attention to the way this element moves through the atmosphere, biosphere, oceans and land. Over the last 500 million years, sulfur seems to have played a fairly crucial role in keeping the oxygen levels in the atmosphere at a nice, breathable 20%.
It is microbes and weather that do the work. Microorganisms in the ocean take in sulfur in the form of dissolved sulfate – that is, in a sulfur…