es5044479_si_001.pdf (998.82 kB)
Secondary Organic Aerosol Formation during Evaporation of Droplets Containing Atmospheric Aldehydes, Amines, and Ammonium Sulfate
journal contribution
posted on 2014-12-16, 00:00 authored by Melissa
M. Galloway, Michelle H. Powelson, Nahzaneen Sedehi, Stephanie E. Wood, Katherine D. Millage, Julia A. Kononenko, Alec D. Rynaski, David O. De HaanReactions of carbonyl compounds in
cloudwater produce organic aerosol
mass through in-cloud oxidation and during postcloud evaporation.
In this work, postcloud evaporation was simulated in laboratory experiments
on evaporating droplets that contain mixtures of common atmospheric
aldehydes with ammonium sulfate (AS), methylamine, or glycine. Aerosol
diameters were measured during monodisperse droplet drying experiments
and during polydisperse droplet equilibration experiments at 75% relative
humidity, and condensed-phase mass was measured in bulk thermogravimetric
experiments. The evaporation of water from a droplet was found to
trigger aldehyde reactions that increased residual particle volumes
by a similar extent in room-temperature experiments, regardless of
whether AS, methylamine, or glycine was present. The production of
organic aerosol volume was highest from droplets containing glyoxal,
followed by similar production from methylglyoxal or hydroxyacetone.
Significant organic aerosol production was observed for glycolaldehyde,
acetaldehyde, and formaldehyde only at elevated temperatures in thermogravimetric
experiments. In many experiments, the amount of aerosol produced was
greater than the sum of all solutes plus nonvolatile solvent impurities,
indicating the additional presence of trapped water, likely caused
by increasing aerosol-phase viscosity due to oligomer formation.