Continuous determination of PM2.5 mass, including semi-volatile species

The Real-Time Ambient Mass Sampler (RAMS) is a real-time ambient monitor fo r the determination of fine particulate mass, including ammonium nitrate an d semi-volatile organic material. Fine particulate mass is continuously mea sured with a TEOM monitor containing a "sandwich" filter to trap any semi-v olatile material (nitrate and organic) lost from collected particles. Gas p hase compounds which will interfere with the TEOM monitor measurement are r emoved using a particle concentrator, diffusion denuders, and dryers. The c oncentrations of these gas phase species are reduced to manageable, but not zero, concentrations prior to the collection of particles on the TEOM prob e. Therefore a second, parallel system preceded by a filter is used to obta in an active blank for the correction of the RAMS monitor data. The results obtained for the continuous determination of PM2.5 with the RAMS have been validated by comparison with results obtained From PC-BOSS diffusion denud er integrated samples to determine the mass of fine particulate material re tained on a filter and the semi-volatile organic material and ammonium nitr ate lost from the filter during sampling. Results obtained with RAMS and de nuder samplers in Prove, UT, Philadelphia, PA, and Atlanta, GA, show that P M2.5 mass, including semi-volatile fine particulate nitrate and organic spe cies, can be continuously and accurately monitored with the RAMS.