Not everywhere in the world is the outflow of hydrocarbons as obvious as in the burning leaks in Azerbaijan (above) and Romania (center) or the bubbles of a mud volcano in Italy. Photos: L. Innocenzi (top) and G. Etiope (middle and bottom), INGV
Reading Gas storage in the earth's crust releases more ethane and propane than thought. The gases are produced together with methane in subterranean camps and volcanically active regions. Italian geologists found out when they examined the concentration of gases in the air at 238 points in the world. This finding closes a gap in the balance of climate models. So far, scientists have attributed the formation of gases mainly to plants and bacteria as well as the use of fuels by humans and agriculture. These sources account for a production of 10 megatons of propane per year and as much ethane. However, scientists came at measurements on propane levels, which indicate an output of at least 15 megatons per year. Most of the missing 5 megatons seep from the ground to the surface and a smaller part escapes from volcanic sources, the Italian researchers now found out.

For their projections, the researchers used the concentration of methane, the most common gas from the family of alkanes, which also includes ethane and propane. Like petroleum, methane is created underground from organic material under pressure and heat for millions of years. In addition to methane, these deposits always contain a small proportion of other alkanes. From previous studies it is known how much methane from the earth's crust swells.

Another source of all three gases is volcanic regions. The researchers observed how much ethane or propane at the investigated sites came to a certain amount of methane, and transferred this ratio to the discharge rate. Thus, at least 17 percent of the ethane emissions and 10 percent of the propane in the atmosphere come from the earth.

Giuseppe Etiope (Istituto Nazionale di Geofisica e Vulcanologia, Rome) and Paolo Ciccioli (Istituto di Metodologie, Chimiche): Science, Vol. 323, p. 478 ddp / Martin Rötzschke advertisement


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