Ground based in situ observations of filter_2pack at Virolahti II (FI0017R). These measurements are gathered as a part of the following projects HELCOM, EMEP and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: ammonium in aerosol (mass_concentration_of_ammonium_expressed_as_nitrogen_in_dry_aerosol_particles_in _air), calcium in aerosol (mass_concentration_of_calcium_in_dry_aerosol_particles_in _air), magnesium in aerosol (mass_concentration_of_magnesium_in_dry_aerosol_particles_in _air), potassium in aerosol (mass_concentration_of_potassium_in_dry_aerosol_particles_in _air), sodium in aerosol (mass_concentration_of_sodium_in_dry_aerosol_particles_in _air)