Continuous Determination of PM2.5Mass, Including Semi-Volatile Species

Abstract

The Real-Time Ambient Mass Sampler (RAMS) is a real-time ambient monitor for the determination of fine particulate mass, including ammonium nitrate and semi-volatile organic material. Fine particulate mass is continuously measured with a TEOM monitor containing a "sandwich" filter to trap any semi-volatile material (nitrate and organic) lost from collected particles. Gas phase compounds which will interfere with the TEOM monitor measurement are removed using a particle concentrator,diffusion denuders, and dryers. The concentrations of these gas phase species are reduced to manageable, but not zero, concentrations prior to the collection of particles on the TEOM probe. Therefore a second, parallel system preceded by a filter is used to obtain 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 denuder integrated samples to determine the mass of fine particulate material retained on a filter and the semi-volatile organic material and ammonium nitrate lost from the filter during sampling. Results obtained with RAMS and denuder samplers in Provo, UT, Philadelphia, PA, and Atlanta, GA, show that PM2.5 mass, including semi-volatile fine particulate nitrate and organic species, can be continuously and accurately monitored with the RAMS.