Ground based in situ observations of pm1_mass at Waldhof (DE0002R) using high_vol_sampler. These measurements are gathered as a part of the following projects EMEP and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: pm1_mass in pm1 (mass_concentration_of_pm1_ambient_aerosol_particles_in_air)