AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Rapid Evaporation of Ultrafine and Fine Particulate Matters in Electronic Cigarette Emissions
Eon Lee, Charlene Nguyen, YIFANG ZHU, University of California Los Angeles
Abstract Number: 83 Working Group: Indoor Aerosols
Abstract Previous studies had reported a rapid decrease of particle number and mass concentrations in electronic cigarette (e-cig) emissions, presumably due to high volatility of e-cig aerosols. There is, however, no direct experiment data about the evaporation of e-cig emitted aerosols. This study aimed to quantify the evaporation rates of e-cig emissions generated from a wide range of e-liquid mixtures in a temperature-controlled chamber. Mimicking the chemical compositions of commercially available e-liquids, ten e-liquid mixtures were prepared from individual chemical compounds of propylene glycol (PG, 99.5%), vegetable glycerin (VG, 99.5%), and nicotine (Nic, 99%). The e-liquid mixtures used in this study had PG/VG volume ratio of 0/100, 10/90, 30/70, 50/50, and 100/0 with and without 2.4 mg Nic/l. Saturation vapor pressures (Psat) of e-liquid mixtures ranged from 10-2 to 20 Pa. In a temperature-controlled chamber, time-series measurements were conducted for the decay of number and mass concentrations for ultrafine particles (UFPs, diameter < 0.1 µm) and fine particulate matters (PM2.5, diameter ≤ 2.5 µm). Finally, the decay rates of e-cig emitted aerosols were compared to the decay rates of DEHS (di-ethyl-hexyl sebacate) aerosols having extremely low volatility (i.e., Psat = ~10-6 Pa). Linear regressions analyses were performed to determine the evaporation rates of UFPs and PM2.5 in e-cig emissions. This study found that the evaporation rate of PM2.5 significantly increased at decreasing relative humidity. Although the evaporation of UFPs had insignificant impacts from the change of relative humidity, the evaporation of UFPs had significant dependence on the change of nicotine content and saturation vapor pressure of e-liquid mixture. The evaporation rate of UFPs was positively proportional to saturation vapor pressure without nicotine. However, with nicotine, the evaporation of UFPs was negatively proportional to saturation vapor pressure potentially because of the protonation of nicotine.