Ground based in situ observations of sulphur_dioxide at Birkenes (NO0001R) using abs_solution. 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: sulphur_dioxide in air (mass_concentration_of_sulphur_dioxide_expressed_as_sulphur_in_air)