Earth's Degassing: A Missing Ethane and Propane Source
Giuseppe Etiope1* and
Paolo Ciccioli2
Current emission inventories require an additional "unknown"
source to balance the global atmospheric budgets of ethane (C
2H
6).
Here, we provide evidence that a substantial part of the missing
source can be attributed to natural gas seepage from petroliferous,
geothermal, and volcanic areas. Such geologic sources also inject
propane (C
3H
8) into the atmosphere. The analysis of a large
data set of methane (CH
4), ethane, and propane concentrations
in surface gas emissions of 238 sites from different geographic
and geologic areas, coupled with published estimates of geomethane
emissions, suggests that Earth's degassing accounts for at least
17% and 10% of total ethane and propane emissions, respectively.
2 Istituto di Metodologie Chimiche, CNR, 00016 Monterotondo Scalo, Italy.
* To whom correspondence should be addressed. E-mail: Etiope{at}ingv.it
