Organic carbon hides in sediments, keeping oxygen in atmosphere

phys.org | 4/12/2018 | Staff
KimmyPoo (Posted by) Level 3
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A new study from researchers at the Woods Hole Oceanographic Institution (WHOI) and Harvard University may help settle a long-standing question—how small amounts of organic carbon become locked away in rock and sediments, preventing it from decomposing. Knowing exactly how that process occurs could help explain why the mixture of gases in the atmosphere has remained stable for so long, says lead author Jordon Hemingway, a postdoctoral researcher at Harvard and former student at WHOI. The paper publishes June 14 in the journal Nature.

Atmospheric carbon dioxide (CO2), Hemingway notes, is an inorganic form of carbon. Plants, algae, and certain types of bacteria can pull that CO2 out of the air, and use it as a building block for sugars, proteins, and other molecules in their body. The process, which occurs during photosynthesis, transforms inorganic carbon into an "organic" form, while releasing oxygen into the atmosphere. The reverse occurs when those organisms die: microbes start to decompose their bodies, consuming oxygen and releasing CO2 back into the air.

Reasons - Earth - Chemical - Cycle - Hemingway

One of the key reasons Earth has remained habitable is that this chemical cycle is slightly imbalanced, Hemingway says. For some reason, a small percentage of organic carbon is not broken down by microbes, but instead stays preserved underground for millions of years.

"If it were perfectly balanced, all the free oxygen in the atmosphere would be used up as quickly as it was created," says Hemingway. "In order to have oxygen left for us to breathe, some of the organic carbon has to be hidden away where it can't decompose."

Evidence - Researchers - Reasons - Carbon - Preservation

Based on existing evidence, researchers have developed two possible reasons why carbon is left behind. The first, called "selective preservation," suggests that some molecules of organic carbon may be difficult for microorganisms to break down, so they remain untouched in sediments once all others have...
(Excerpt) Read more at: phys.org
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