VALIDATION OF PASSIVE DIFFUSION SAMPLERS FOR SO2 AND NO2

Passive diffusion samplers of the type described by Ferm (1991) were t ested at sites in Australia for measurement of ambient levels of SO2 a nd NO2. For samplers exposed over periods of one to four weeks the pas sive diffusion samplers were found to provide quantitative measurement s of these gases. Precision of the samplers, expressed as mean percent age difference between duplicates, was in the range 5-10% for NO2 at s imilar to 15 ppbv and 25-10% for SO2 in the range 0.5-5 ppbv. Experime nts with passive NO2 samplers of different lengths confirmed the predi ction by Heal and Cape (Atmospheric Environment 31, 1911-1923) of a si gnificant artefact due to chemical reactions within the sampler, but a lso confirmed that the short tube length employed by the Ferm-type sam pler renders this artefact insignificant for these samplers. (C) 1998 Elsevier Science Ltd. All rights reserved.