THE STEAM-JET AEROSOL COLLECTOR

A new principle of sampling aerosol particles by means of steam inject ion with the consequent collection of grown droplets has been establis hed. An air stream free of water-soluble gases is rapidly mixed with s team. The resulting supersaturation causes aerosol particles to grow i nto droplets. The droplets containing dissolved aerosol species are th en collected by two cyclones in series. The solution collected in the cyclones is constantly pumped out and can be on- or off-line analysed by means of ion chromatography or flow injection analysis. On the basi s of the new sampling principle a prototype of an aerosol sampler was designed which is capable of sampling particles quantitatively down to several nanometres in diameter. The mass sampling efficiency of the i nstrument was found to be 99%. The detection limit of the sampler for ammonium, sulphate, nitrate and chloride ions is below 0.7 mu g m(-3). By reduction of an already identified source of contamination, much l ower detection limits can be achieved. During measurements the sampler proved to be stable, working without any assistance for extended peri ods of time. Comparison of the sampler with filter packs during measur ements of ambient air aerosols showed that the sampler gives good resu lts.