Aerosol collection by cascade impaction and filtration: Influence of different sampling systems on the measured organic pollutant levels

Abstract

A comparison is made between the analytical data obtained for the organic composition of airborne particulate matter collected with a high volume cascade impactor and a filtration sampler. The concentrations of individual organic pollutants are determined by gas chromatography—mass spectrometry. The total suspended particulate matter concentrations agree within 10% or better for the two samplers. The individual concentrations of pollutants agree in most cases within 20 to 30%. It is concluded that both sampling and analytical procedures give consistent results for organic compounds of low volatility. These are preferentially associated with the smaller particles (<3 μm) whose collection efficiency is not affected by differences in upper cut-off diameter of the two samplers. Deviations in concentration levels beyond 20 to 30% occur for organic compounds of high volatility such as the lower molecular weight polyaromatics, the lower carboxylic acids and the aliphatics. Therefore, it is believed that volatilisation of compounds from the filter substrate may be an important source of errors in the measurement of organic pollutant levels in aerosols.