Characterization of an Aerodyne Aerosol Mass Spectrometer (AMS): Intercomparison with Other Aerosol Instruments

The Aerodyne Aerosol Mass Spectrometer (AMS) provides size-resolved chemical composition of non-refractory (vaporized at 600°C under vacuum) submicron aerosols with a time resolution of the order of minutes. Ambient measurements were performed in Tokyo between February 2003 and February 2004. We present intercomparisons of the AMS with a Particle-Into-Liquid Sampler combined with an Ion Chromatography analyzer (PILS-IC) and a Sunset Laboratory semi-continuous thermal-optical carbon analyzer. The temperature of the AMS inlet manifold was maintained at > 10 ^ˆ C above the ambient dew point to dry particles in the sample air (relative humidity (RH) in the inlet < 53%). Assuming a particle collection efficiency of 0.5 for the AMS, the mass concentrations of inorganic species (nitrate, sulfate, chloride, and ammonium) measured by the AMS agree with those measured by the PILS-IC to within 26%. The mass concentrations of organic compounds measured by the AMS correlate well with organic carbon (OC) mass measured by the Sunset Laboratory carbon analyzer (r ² = 0.67–0.83). Assuming the same collection efficiency of 0.5 for the AMS organics, the linear regression slope is found to be 1.8 in summer and 1.6 in fall. These values are consistent with expected ratios of organic matter (OM) to OC in urban air.

Acknowledgments

This study was funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and the Japanese Science and Technology Agency (JST).

Notes

^a Average ± standard deviation. Values in parentheses represent minimum and maximum values.

^b Particle-Into-Liquid Sampler combined with Ion Chromatography (PILS-IC).

^c Semi-continuous thermal-optical carbon analyzer manufactured by the Sunset Laboratory, Inc.

^d N/A: Not available.

^a The LOD (Ion counting) is defined as the concentration needed to produce a signal-to-noise ratio (SNR) of 3 above the dominant source of noise due to background ions from the mass spectrometer.

^b The LOD (Filter) is defined as 3 times the standard deviation of the mass concentration measured by placing a particle filter in front of the AMS.

^a Linear regression fit parameters of AMS versus PILS-IC or OC correlation. Errors are 95% confidence intervals.