Ground based in situ observations of mercury_GEM at Birkenes II (NO0002R) using Hg_mon. These measurements are gathered as a part of the following projects CAMP, EMEP, NILU and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: mercury_GEM in air (mass_concentration_of_gaseous_elemental_mercury_in_air)