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SUMMARY:Chemical heterogeneities in atmospheric organic particles and thei
 r implications for aerosol-water interactions
DTSTART:20110721T101500
DTSTAMP:20260924T173820Z
UID:c8cc9fcb2f779b37e567a35b241163a94cb64f49404b78d20294285f
CATEGORIES:Conferences - Seminars
DESCRIPTION:Satoshi Takahama\nAirborne particulate matter have been associ
 ated with excess mortality and play an important role in the radiative bal
 ance of the atmosphere.\nThe organic fraction of these particles  or aeros
 ols  represent one of the largest uncertainties in our ability to quantify
  atmospheric burdens and climate feedbacks. Among our uncertainties regard
 ing\nthese aerosols include particle shape and distribution of chemical co
 mpounds within individual particles  which are implied in models used for 
 prediction of radiative transfer  volatility  and mass\ntransfer. In this 
 talk  a combination of measurement and modeling techniques describing chem
 ical heterogeneities and their implications for could-forming properties o
 f organic aerosols are presented. The chemical structure of organic and ca
 rbonaceous particles collected in six field campaigns in the western hemis
 phere is probed by image analysis and pattern recognition techniques appli
 ed to single particles analyzed by Scanning Transmission X-Ray Microscopy 
 with Near-Edge X-Ray Absorption Fine Structure Spectroscopy. A few observe
 d types include black carbon particles covered by organic and other aqueou
 s-phase components  organic clumps found on dust particles  particles enri
 ched in carboxylic acids at the surface  and inorganic cores encapsulated 
 by organic shells. Quantified coating thicknesses are calculated to have a
  significant impact on the equilibrium water uptake properties of these pa
 rticles. Dynamic uptake properties of water vapor onto particle surfaces c
 oated with organic layers are additionally investigated through a series o
 f molecular simulations  which allow an atomistic examination of surface-v
 apor interactions and quantification of mass accommodation coefficients. T
 hese findings are placed in context of observed coating thicknesses and fo
 rmation of cloud droplets from particles containing such coatings.
LOCATION:CM 1 1 https://plan.epfl.ch/?room==CM%201%201
STATUS:CONFIRMED
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