Acidic Aerosol Size Distributions during SCAQS (Southern California Air Quality Study)

摘要

Ambient aerosol in the size range 0.075 - 16 micrometers was sampled with Berner cascade impactors during the summer and fall intensive sampling periods of the Southern California Air Quality Study (SCAQS) of 1987. Stage mass data were inverted by a modified version of the Twomey nonlinear iterative algorithm and modes in the inverted size distributions were fitted with lognormal functions. During SCAQS, most of the inorganic particle mass was in the droplet mode except during a period of exceptionally low relative humidity. Nitrate was internally mixed with sulfate in the droplet mode. Since most of the aerosol fine mass is included in the ions analyzed, the observed condensation and droplet modes characterize the overall size distribution in the 0.1-1 micrometer range, previously described by Whitby as a single accumulation mode.