Friday, September 8, 2017 -
12:00pm to 1:00pm
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Pierce 100F, 29 Oxford St, Cambridge

Atmospheric & Environmental Chemistry Seminar

Manabu Shiraiwa, University of California – Irvine, will give a talk on "Molecular Corridors and Particle Phase State in Atmospheric Secondary Organic Aerosols."

Secondary organic aerosols (SOA) are ubiquitous in the atmosphere. The phase state of SOA is important for their effects on climate and air quality, but its global distribution is poorly characterized. Our analysis of SOA phase state builds on the molecular corridor approach, which is a two-dimensional framework of volatility and molar mass of SOA components constrained by boundary lines of low and high molecular O:C ratio. We developed a method to estimate glass transition temperatures and viscosity based on the molar mass and molecular O:C ratio of SOA components, and we used the global chemistry climate model EMAC with the organic aerosol module ORACLE to predict the phase state of atmospheric SOA. For the planetary boundary layer, global simulations indicate that SOA are mostly liquid in tropical and polar air with high relative humidity, semi-solid in the mid-latitudes, and solid over dry lands. We find that in the middle and upper troposphere SOA should be mostly in a glassy solid phase state. Thus, slow diffusion of water, oxidants, and organic molecules could kinetically limit gas-particle interactions of SOA in the free and upper troposphere, promote ice nucleation and facilitate long-range transport of reactive and toxic organic pollutants embedded in SOA.

Speaker Bio

Contact Name: 

Pengfei Liu

Research Areas: 

Harvard University
Center for the Environment

Address: 26 Oxford Street, 4th Floor, Cambridge
Phone: (617) 495-0368

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