Model helps detect CO2 leaks

New method could assist in the monitoring of CO2 storage in the sea

For future CO2 storage under the seabed, gas leaks must be detected quickly. © Christian Howe,
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Leakage: CO2 storage under the seabed is being discussed as a climate change strategy - but critics are worried about possible leaks. Researchers have now developed a model that could help monitor such underground GHG deposits in the future. It predicts amazingly precisely how the pH values ​​in the water change in the vicinity of carbon dioxide emissions.

The global climate protection efforts are making slow progress. Instead of producing less greenhouse gas emissions, humanity is even releasing more CO2. In the meantime, more and more researchers are calling for alternative solutions such as CCS technology. The carbon dioxide is actively drawn from the air and then stored, for example, deep under the seabed.

Off the coast of Norway, there is already such a facility for the capture and storage of CO2. But the approach is not undisputed. Among other things, critics fear that the greenhouse gas could re-emerge through leaks. In the sea, this would mean a lower risk than on land, because the gas dissolves in the sea water. However, the associated changes in pH could harm marine life and alter marine ecosystems.

Test on natural sources

The problem: "There is currently no established method for locating potential carbon dioxide leakage and determining the total amount of gas escaping when the exit points extend over a several hundred square meter area, " explains Jonas Gros of the GEOMAR Helmholtz Center for Ocean Research in Kiel. That's why the scientist and his colleagues have now developed a computer model that could help in the future.

The new model predicts pH changes in seawater due to carbon dioxide emissions. But how does it work? To test this, the research team looked at natural CO2 sources on the seabed: Near the island of Panarea off the coast of northern Sicily there are over 200 such carbon dioxide exit sites. In their surroundings, Gros and his colleagues took gas and water samples and studied how the pH around the outlets changed. display

Data and forecast are consistent

The results revealed that the measured data agreed remarkably well with the predictions of the model. Thus, the model was able to predict the patterns of pH variation in the water around the gas wells relatively accurately. It also showed that more than 79 percent of the gaseous carbon dioxide is dissolved in the water at a distance of four meters from the seabed.

In the future, the model may help the designer to plan leak detection strategies. "In addition, the new model can be used to estimate the impact of carbon dioxide emissions on the local marine environment, " says Gros. (Environmental Science & Technology, 2019, doi: 10.1021 / acs.est.9b02131)

Source: GEOMAR Helmholtz Center for Ocean Research Kiel

- Daniel Albat