Use of the RAMS to Measure Semivolatile Fine Particulate Matter at Riverside and Bakersfield, California

Fine particles in urban environments contain substantial quantities of material that can be lost from the particles during sample collection on a filter. This materials include ammonium nitrate and semivolatile organic compounds. Methods for the accurate determination of these species in integrated samples have been developed using diffusion denuder samplers. However, it is often desirable to determine fine particulate matter on a continuous basis. The real-time ambient mass sampler (RAMS), a continuous monitor using diffusion denuder and tapered element oscillating microbalance (TEOM) technologies, has been evaluated by monitoring fine particulate species in Riverside, CA during August and September, 1997, and in Bakersfield, CA during February and March, 1998. The results are compared to measurements made in 1 h integrated samples in Riverside and in 2 h integrated samples in Bakersfield with a diffusion denuder sampler, the particle concentrator-Brigham Young University organic sampling system (PC-BOSS). An average of 5% of the Riverside fine particulate matter was present as semivolatile ammonium nitrate and 33% as semivolatile organic material that was lost from a PC-BOSS filter during sampling. In Bakersfield the fraction of PM 2.5 lost from a PC-BOSS filter averaged 3% as semivolatile ammonium nitrate and 15% as semivolatile organic material. These species were correctly determined by the RAMS. However, the usefulness of the RAMS as a continuous monitor is limited by the blank variability with the design presented here.