Ambient particles contain substantial quantities of material that canb e lost from the particles during sample collection on a filter, including ammonium nitrate and semivolatile organic compounds. The real-time ambient mass sampler (RAMS) described in this paper has been developed for the accurate containous monitoring of fine particulate material. The previously published verison of the RAMS had signficant problems with a variable blank correction. A series of experiments conducted in Provo, UT, during December, 1998, indicated that nitrogen oxides and water were the major contributors to a high morning black. This blank was minimized by heating theBrigham Young Univerity Organic Sampling System (BOSS) charcoal diffusion denuder and adding mutlichannel annual denuders coated with triethanolamine (TEA) to remove No-2. This new configuration of the RAMS was used to collect samples on 5 consecutive days in Provo, UT. These results wer compared to measuremtns made in both 6 h and 24 h integrated samples using the Particle Concentrator-BOSS (PC-BOSS) An average of 1 of the Provo fine particulate material was present as ammonium nitrate and 15 as semivolatile organic material, which were lost from a filter during sampling for samples collected over 24 h and 6 h average periods. These species were correctly determined by the RAMS.
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