Measurements of water uptake property of atmospheric aerosols at elevated relative humidity

Abstract

The hygroscopic property (water uptake property at elevated relative humidity) of atmospheric aerosols is essential to understand the effect of aerosols on cloud formation by acting as cloud condensation nuclei (CCN) (i.e., hygroscopic particles grow into the CCN by absorbing water), which leads to climate change with cloud albedo effect. Also, hygroscopic property of particles is important to determine their transport behaviors and fates in the ambient atmosphere and to understnd their deposition pattern in the human respiratory system when they were inhaled. In this chapter, first, we describe a hygroscopicity tandem differential mobility analyzer (HTDMA) system in details to measure hygroscopic property of atmospheric aerosols in real time by measuring particle size change at an increased relative humidity. Then, we applied the HTDMA system to determine hygroscopic growth factors (i.e., ratio of particle size increase under high relative humidity) of various laboratory-generated particles of known composition and size to evaluate the performance of the HTDMA system. Finally, the hygroscopic GFs of particles in the ambient atmosphere at the relative humidity of 85% in various atmospheric environments (urban, rural, and coastal sampling sites) were measured and their results were compared. This will provide the estimation of chemical constituents of atmospheric aerosols in different environments, leading to a better understanding of their source characteristics. © 2011 by Nova Science Publishers, Inc. All rights reserved.