Ground based in situ observations of low_vol_sampler at Harwell (GB0036R). These measurements are gathered as a part of the following projects EMEP, GAW-WDCA, EUSAAR and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: chloride in pm10 (mass_concentration_of_chloride_in_pm10_in_air), sulphate_total in pm10 (mass_concentration_of_sulphate_total_in_pm10_in_air)