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Giorgio Caramanna
Natural Analogues How we can learn from nature
Potential environmental effects of CO2 leakage in marine and terrestrial
environments: Understanding, monitoring, mitigation workshop 21st February 2012 – The University of Nottingham
• Natural analogues
Where can we find them?
Why are they useful?
What can we investigate?
• A terrestrial example: the caldera of Laacher See (Germany)
• A marine example: shallow-water emissions in Italy and deep-water emissions in Japan
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Outline
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Natural analogues
• CO2 vents can be found in terrestrial and aquatic environments and are generally associated with volcanic and geothermal active areas.
• The source of the CO2 can be a degassing magmatic body, the mantle or even the thermal decomposition of limestone bedrock.
• The CO2 concentration of the emitted gas is variable and there is often some % of other gases, typically SO2 and H2S.
• The fluxes range from a few litres to hundreds of litres per minute.
• The vents follow the tectonic lineaments.
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Why natural analogues are useful
• The boundary conditions are far more realistic than any possible laboratory simulation.
CO2 is generally emitted through large areas.
The emissions have lasted a long time.
There is a well-developed ecosystem.
• They can be used to validate results from laboratory experiments and modelling.
• They can be used to test instruments and methods for CO2 seepage detection and monitoring.
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Parameters to investigate
• CO2 concentrations as free or dissolved gas
Soil gas sampling
Airborne survey
Eddy covariance
Dissolved gas sensor
• Chemical impact
pH variations
Metals mobilization
• Biological impact
Microbes
Vegetation
Animals
Laacher See
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• The lake occupies one of about 100 quaternary eruptive centres which spread over an area of 330 km2 in the East-Eiffel volcanic province (Germany).
• The source of the CO2 is in the upper mantle from where Mg-rich magma, formed by the melting of peridotite, transports and releases the gas through the lower and upper crust.
• The CO2 interacts with the groundwater originating high-mineralized springs.
• The lake has a maximum depth of 52 m and CO2 vents are located mostly along its north-eastern shore and along some alignments underwater.
• The emitted CO2 is estimated at about 5,000 t/year.
Laacher See natural analogue
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Gas eruption and shallow-water
ROV video courtesy of CO2GeoNet
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Pictures courtesy of BGS
I. R. and Eddy Covariance
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Kagoshima Bay
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• The Aira caldera and its post-caldera active volcano Sakurajima are the dominant features of Kagoshima Bay.
• The caldera is supposed to be more than 22 *103 years old. The last eruption of the Sakurajima was in 1914 and since 1955 there is a continuous ash emission from the crater.
• The maximum depth of the caldera is 200 m.
• On the seafloor, some vents emit high temperature fluids (215oC) and gas composed of CO2, H2S, CH4 and N2.
• The vents have been studied by means of manned submersibles and unmanned vehicles.
Kagoshima Bay natural analogue
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AUV and ROV in deep-water
Courtesy of Kyushu University
Panarea Island
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Main vents location
• Submerged caldera with emission of gas (mainly CO2) close to the island of Panarea (Italy).
• In 2002, the area was affected by a gas burst with a strong increase in the CO2 flow likely originated from a degassing magmatic body.
• The flux of the vented CO2 ranges from a few litres to more than 150 litres/minute with a total flux of up to 70,000 t/year.
•Due to the environmental conditions and the relatively shallow water, it is possible to use the island as field-lab for the development of monitoring techniques and to verify the impact of high levels of CO2 on the marine ecosystem at costs almost negligible as compared to high-seas research.
Panarea natural analogue
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Divers in shallow water
Courtesy of The University of Nottingham
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Free gas composition
0.00
10.00
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30.00
40.00
50.00
60.00
70.00
80.00
90.00
%
Average free gas composition October 2011
O2 CO2 N2 H2S
3.91 5.68 1.55
89.37
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pH variations
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Lessons learned
• Reliability of detection and monitoring techniques.
CO2 is clearly identifiable as gas and from the pH decrease.
Geochemical techniques are a reliable tool.
Biological stress (vegetations, microbes, macro life-forms) can be used to identify the presence of CO2 values above the baseline.
• The presence of gases other than CO2 should be addressed for the realistic interpretation of the results.
• Good potentiality of natural analogues to be used as testing facilities for innovative techniques and detection instruments.
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Acknowledgements
• The University of Nottingham
• The Kyushu University and Dr. Kiminori Shitashima
• The University of Plymouth and Dr. Riccardo Rodolfo-Metalpa for his diving collaboration in Panarea
•The INGV and Dr. Nunzia Voltattorni for the Panarea gas analysis.
• The BGS
• The CO2GeoNet
• The BGR
•All of the colleagues who collaborated on the fieldwork activity
•The NCCCS for hosting this workshop
Thank you for your kind attention!
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Questions?
