Phase state of ambient aerosol linked with water uptake and chemical aging in the Southeastern US Journal Article uri icon

Overview

abstract

  • Abstract. During the summer 2013 SOAS field campaign in a rural site in the Southeastern United States, the effect of hygroscopicity and composition on the phase state of atmospheric aerosol particles dominated by the organic fraction was studied. The analysis is based on hygroscopicity measurements by a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA), physical phase state investigations by an Aerosol Bounce Instrument (ABI), and composition measurements using a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). To study the effect of atmospheric aging on these properties an OH-radical oxidation flow reactor (OFR) was used to simulate longer atmospheric aging times of up to three weeks. Hygroscopicity and bounce behavior of the particles had a clear relationship showing higher bounce at elevated RH values for less hygroscopic particles which agrees well with earlier laboratory studies. Additional OH oxidation of the aerosol particles in the OFR increased the O:C and the hygroscopicity resulting in liquefying of the particles at lower RH values. At the highest OH exposures, the inorganic fraction starts to dominate the bounce process due to production of inorganics and concurrent loss of organics in the OFR. At typical ambient RH and temperature, organic dominated particles stay mostly liquid in the atmospheric conditions in the Southeastern US, but they often turn semisolid when dried below ~ 50 % RH in the sampling inlets. While the liquid phase state suggests solution behavior and instantaneous equilibrium partitioning for the SOA particles in ambient air, the possible phase change in the drying process highlights the importance of thoroughly considered sampling techniques of SOA particles.;

publication date

  • May 9, 2016

has restriction

  • green

Date in CU Experts

  • November 13, 2020 4:26 AM

Full Author List

  • Pajunoja A; Hu W; Leong YJ; Taylor NF; Miettinen P; Palm BB; Mikkonen S; Collins DR; Jimenez JL; Virtanen A

author count

  • 10

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