AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
An Algorithm to Derive Particle Size Changes from Full size Distribution Measurements
CHIRANJIVI BHATTARAI, Andrey Khlystov, Desert Research Institude
Abstract Number: 486 Working Group: Single Aerosol Particle Studies - Techniques and Instrumentation
Abstract One of the major uncertainties in understanding the Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. Aerosols exposed to high humidity and temperature will change their chemical, physical, and optical properties. Volatility and hygroscopic growth factors of aerosols are usually studied using the tandem differential mobility analyzer (TDMA) method. The TDMA method takes a relatively long time to complete a measurement at several sizes. Quicker methods to make such measurements are needed. We have used measurements of full size distributions before and after an aerosol underwent a physical change to determine how the change affected particles of different sizes. This was done using an inversion algorithm that is based on preservation of particle number. Using cumulative distributions, we find particle sizes in both distributions corresponding to a certain number concentration. This provides sizes of particles before and after transformation (evaporation or growth). This approach has been proposed and used in late 1970’s and early 1980's [1, 2]. However, to our knowledge, there has been no experimental verification reported until now. In this study, we performed a detailed theoretical and numerical analysis of uncertainties associated with this algorithm. We also have carried out a set of experiments using adipic acid aerosol evaporation as an example. The inversion algorithm applied to full size distribution measurements provided results that are within 10 % of TDMA measurements.
References:
1. Heisler, Steven Ludvic, and S. K. Friedlander. "Gas-to-particle conversion in photochemical smog: aerosol growth laws and mechanisms for organics." Atmospheric Environment (1967) 11.2 (1977): 157-168.
2. McMurry, P. H., and J. C. Wilson. "Growth laws for the formation of secondary ambient aerosols: implications for chemical conversion mechanisms." Atmospheric Environment 16.1 (1982): 121-134.