Key To Speeding Up Carbon Sequestration Discovered

2017-07-20T10:56:03+00:00 July 20, 2017|
Acidified ocean water can eat away at coral reefs.(Credit: ARC COE for Coral Reef Studies/Marine Photobank/Reuters)

(Click to enlarge) Acidified ocean water can eat away at coral reefs.(Credit: ARC COE for Coral Reef Studies/Marine Photobank/Reuters)

Scientists at Caltech and USC have discovered a way to speed up the slow part of the chemical reaction that ultimately helps Earth to safely lock away, or sequester, carbon dioxide into the ocean.

(From Science Daily) — Simply adding a common enzyme to the mix, the researchers have found, can make that rate-limiting part of the process go 500 times faster.

A paper about the work appears online the week of July 17 ahead of publication in the Proceedings of the National Academy of Sciences.

“While the new paper is about a basic chemical mechanism, the implication is that we might better mimic the natural process that stores carbon dioxide in the ocean,” says lead author Adam Subhas, a Caltech graduate student and Resnick Sustainability Fellow.

The research is a collaboration between the labs of Jess Adkins from Caltech and Will Berelson of USC. The team used isotopic labeling and two methods for measuring isotope ratios in solutions and solids to study calcite — a form of calcium carbonate — dissolving in seawater and measure how fast it occurs at a molecular level.

It all started with a very simple, very basic problem: measuring how long it takes for calcite to dissolve in seawater. “Although a seemingly straightforward problem, the kinetics of the reaction is poorly understood,” says Berelson, professor of earth sciences at the USC Dornsife College of Letters, Arts and Sciences.

Calcite is a mineral made of calcium, carbon, and oxygen that is more commonly known as the sedimentary precursor to limestone and marble. In the ocean, calcite is a sediment formed from the shells of organisms, like plankton, that have died and sunk to the seafloor. Calcium carbonate is also the material that makes up coral reefs — the exoskeleton of the coral polyp.

As atmospheric carbon dioxide levels have risen past 400 parts per million — a symbolic benchmark for climate scientists confirming that the effects of the greenhouse gas in the atmosphere will be felt for generations to come — the surface oceans have absorbed more and more of that carbon dioxide. This is part of a natural buffering process — the oceans act as a major reservoir of carbon dioxide. At the present time, they hold roughly 50 times as much of the greenhouse gas as the atmosphere.

However, there is a second, slower, buffering process that removes carbon dioxide from the atmosphere. Carbon dioxide is an acid in seawater, just as it is in carbonated sodas (which is part of why they eat away at your tooth enamel). The acidified surface ocean waters will eventually circulate to the deep where they can react with the dead calcium carbonate shells on the sea floor and neutralize the added carbon dioxide. However, this process will take tens of thousands of years to complete and meanwhile, the ever-more acidic surface waters eat away at coral reefs. But how quickly will the coral dissolve?

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