Ground based in situ observations of online_IC at Harwell (GB0036R). These measurements are gathered as a part of the following projects EMEP, CAMPAIGN and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: ammonium in pm10_pm25 (mass_concentration_of_ammonium_in_pm10_minus_pm2p5_in_air), ammonium in pm25 (mass_concentration_of_ammonium_in_pm2p5_in_air), chloride in pm10_pm25 (mass_concentration_of_chloride_in_pm10_minus_pm2p5_in_air), chloride in pm25 (mass_concentration_of_chloride_in_pm2p5_in_air), nitrate in pm10_pm25 (mass_concentration_of_nitrate_in_pm10_minus_pm2p5_in_air), nitrate in pm25 (mass_concentration_of_nitrate_in_pm2p5_in_air), sulphate_total in pm10_pm25 (mass_concentration_of_sulphate_total_in_pm10_minus_pm2p5_in_air), sulphate_total in pm25 (mass_concentration_of_sulphate_total_in_pm2p5_in_air)