A new volatility tandem differential mobility analyzer to measure the volatile sulfuric acid aerosol fraction

A volatility tandem differential mobility analyzer (VTDMA) was developed wi th the intention to measure the fraction of sulfuric acid in marine fine ae rosols (D-p < 150 nm). This work focused on the design and calibration of a n aerosol conditioner for the standard tandem differential mobility analyze r that heated a selected aerosol sample in a controlled manner while it min imized sample losses due to thermophoresis and diffusion. In designing an a erosol heater, the behavior of a monodisperse aerosol was modeled in a heat ed how tube with a temperature-controlled wall under laminar flow condition s. This allowed for initial estimations of aerosol heating rates, heater di mensions, and aerosol deposition losses within the flow tube. The evaporati on rate of sulfuric acid particles was also predicted and used to determine the minimum length of the aerosol heater needed to completely evaporate a sulfuric acid aerosol. Finally, the VTDMA was calibrated and tested for its ability to detect a sulfuric acid mass fraction in a monodisperse aerosol.