San Francisco, Calif. -- The often lethal carbon dioxide springs that dot central and south-central Italy, may hold the key to understanding current and ancient levels of this greenhouse gas, according to Penn State geoscientists.
"Generally, when researchers compute total non-anthropogenic carbon dioxide flux, non-volcanic sources such as central and south-central Italy are ignored," says Dr. Derrill Kerrick, professor of geoscience. "However, the contribution from areas like Italy can be quite sizable."
Carbon dioxide in the atmosphere contributes to greenhouse warming and climate change. Volcanoes have long been thought the major contributor of carbon dioxide, but there are large areas with vents expelling non-volcanic carbon dioxide in Italy, California and other places. While volcanoes produce the gas from magma, the carbon dioxide vents in Italy are expelling gas generated at depth from metamorphism of rocks that were formed by marine organisms and are composed of calcium carbonate.
The 200-mile area of Italy between Florence and Naples produces an enormous amount of carbon dioxide, yet no one has tried to measure the amount before, the researchers told attendees today (Dec. 17) at the fall meeting of the American Geophysical Union in San Francisco. We don't have a sense of how much is going into the atmosphere, they said.
"People have known about these springs for a long time," says John D. Rogie, graduate student in geosciences. "At Acqua Terme, the boiling water and carbon dioxide geyser is encased in glass and is part of a spa resort." In one location, the researchers note, a spring has been cased and tapped to supply carbon dioxide to a Coca Cola bottling plant.
"These sites are locally known, but not generally publicized outside of Italy," says Kerrick. "Some produce virtually 100 percent carbon dioxide and are quite lethal. The area around such vents is typically littered with animal carcasses and people have died in these areas."
One reason these places are so lethal is that carbon dioxide is invisible and heavier than air. The gas sits on the ground and flows to low areas. Animals and humans caught in these areas can be killed before they have time to leave.
Kerrick and Rogie are working with a team of Italian scientists including G. Chiodini and F. Frondini from the Dipartmento Scienza Della Terra, University of Perugia; Franceso Parello of the University of Palermo and Angelo Minissale of the University of Florence. The Italians already have a home-made device for measuring the flow of carbon dioxide from vents and the researchers have made a variety of devices to measure the diffuse degassing through the soil.
"We estimate that there are between 150 and 200 carbon dioxide vents in this area of Italy," says Kerrick. "One vent east of Naples emits over 200 tons of carbon dioxide per day."
The researchers note that emissions from some vents are equivalent to that of some volcanoes. The flux from the vent east of Naples is equivalent to the combined crater and diffuse flux from Vulcano, a volcanic island near Sicily.
When looking at diffuse degassing, the researchers found one area that measured less than a tenth of a square mile, yet emits 150 tons of carbon dioxide per day.
The researchers note that Mt. Etna, a volcano which produces 35,000 tons of carbon dioxide per day and is the largest single source of natural carbon dioxide in the world, is located in this area of Italy. Unlike many other volcanoes, Etna is not in an area where tectonic plates meet.
Assuming that most carbon dioxide in the past came from areas of subduction vulcanism may not be the way to model carbon dioxide production, according to the researchers. There is a great deal of gas coming from carbon dioxide vents and the area around these vents that must be taken into consideration.
EDITORS: Dr. Kerrick may be reached at (814) 865-7574. Mr. Rogie may be reached
at (814) 863-7265. Photos are available on request and after December 17 at http://www.