Fast Time Response Measurements of Aerosol Composition by Chemical Ionization Mass Spectrometry

Fast and accurate measurements of atmospheric aerosol composition is an important part of quantifying and understanding atmospheric pollution and its consequences. Such data can be used for studies of regional haze analysis, development of atmospheric models, atmospheric aerosol source apportionment and aerosol and gas interactions. This presentation describes the development of a new technique for the measurement of atmospheric aerosol composition. A negative ion Chemical Ionization Mass Spectrometry (CIMS) method has been used to perform 1 Hz aerosol composition measurements. A heated inlet is used to evaporate ambient aerosol with subsequent detection of the evolved gases. Two reagent ions, bromide and nitrate, have been used to selectively detect acidic components of the aerosols such as sulfate, nitrate, malonate, and oxalate. The CIMS sulfate measurements in ambient air were compared with a Particle into Liquid Sampler (PILS). These tests showed a high degree of correlation between the measurements and strongly suggest that the CIMS can measure sulfate with a high degree of selectivity and sensitivity. Further tests suggest that CIMS method may be able to also perform selective measurements of a few strong organic acids such as oxalic.