Ground based in situ observations of filter_3pack at Risoe (DK0012R). These measurements are gathered as a part of the following projects CAMP, EMEP, HELCOM and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: arsenic in aerosol (mass_concentration_of_arsenic_in_dry_aerosol_particles_in _air), cadmium in aerosol (mass_concentration_of_cadmium_in_dry_aerosol_particles_in _air), lead in aerosol (mass_concentration_of_lead_in_dry_aerosol_particles_in _air), nickel in aerosol (mass_concentration_of_nickel_in_dry_aerosol_particles_in _air)