13. Evaluation and examination particle transmission through traditional denuders and through different configuration of carbon-impregnated foam

Patrick Lee, Gang Lu, Jeffrey Brook*
Meteorological Service of Canada, Environment Canada, Toronto, Canada (*corresponding author: Jeffrey.brook@ec.gc.ca).

Key Words: Organic aerosol, PM2.5, carbon foam, SMPS, APS

Introduction:
There is considerable awareness of the influence of fine particulate matter (PM2.5) on environmental system and human health. Due to the numerous types of chemical species and a wide range of chemical and thermodynamic properties that comprise organic aerosols, accurate sampling of organic aerosols has been a very challenging task. Both "positive" and it negative" artifacts associated with the collection of PM2.5 by traditional organic aerosol sampling approaches are anticipated. The "positive" artifact results from the adsorption of gas-phase organic compounds by a quartz filter.

Traditional technique to eliminate "positive" artifact is using diffusion denuder. Denuders are used to first remove gaseous OC from the sample air-stream before collecting the particles on a filter. More recently, a novel sampling approach has been tested which utilizes carbon-impregnated foam to remove gas phase VOC and SVOC upstream from the quartz filter to eliminate the positive artifact.

The particle penetration through the carbon foam and/or denuder is a key performance parameter when using above approaches as gas phase VOC eliminator during the organic aerosol sampling. In this study, we used SMPS, APS and CPC to investigate particle transmission efficiency through different grades of the carbon-impregnated foam in comparison to transmission through the IOGAPS denuder.

Methods and Instrumentation:
The scanning mobility particle spectrometer (SMPS) selecting particles based upon their mobility in an electrical field. The system employs an electrostatic classifier to determine particle size (measuring submicrometer aerosols in the range from 10 to 500 manometers in diameter), and a condensation particle counter (CPC) to determine particle concentration.

An Aerodynamic Particle Sizer (APS) (with counter) was also used to determine the concentration of aerosol with aerodynamic diameter in the range of 0.5 to 25 um. Thus, both SMPS and APS cover the aerodynamic diameter range of PM2.5.

The PM2.5 particles were introduced into SMPS and APS through ambient air as well as through aerosol generation.

Results:
The experimental results will be presented for denuders and for different configurations of carbon foam, such as foam thickness, the amount of active carbon on the foam (pores per inch), face velocity and the number of disks of foam that could be packed together without causing particle loss to the foam(s).