Romania is one of the European countries with the most vigorous natural seepage of methane, uprising from
pressurised natural gas and petroleum reservoirs through deep faults. The largest seepage zone is represented by
large mud volcanoes, with CH4 >80% v/v, occurring on the Berca-Arbanasi hydrocarbon-bearing faulted anticline,
in the Carpathian Foredeep. Smaller mud volcanoes have been identified in other areas of the Carpathian
Foredeep, in the Transylvanian Depression and on the Moldavian Platform. New surveys carried out in Transylvania
allowed us to discover the richest N2 mud volcano zone in the world (N2>90% v/v), with a remarkably
high He content and a helium isotopic signature which highlights a contribution of mantle-derived source. The
large mud volcanoes are generally quiescent, with rare explosive episodes and provide a methane flux in the order
of 102-103 t km−2 y−1. Independently from mud volcanism, a remarkable dry macroseepage, however, has been
found, with a degassing rate up to three orders of magnitude higher than that of mud volcanoes (i.e. 103-105 t
km−2 y−1). The total gas flux from all investigated macroseepage zones in Romania is estimated in the range of
1500-2500 t y−1. The emission from microseepage, pervasively occurring throughout the hydrocarbon-prone
basins, has yet to be assessed and added to the total gas output to the atmosphere
