1 research outputs found
Uptake of Epoxydiol Isomers Accounts for Half of the Particle-Phase Material Produced from Isoprene Photooxidation via the HO<sub>2</sub> Pathway
The
oxidation of isoprene is a globally significant source of secondary
organic material (SOM) of atmospheric particles. The relative importance
of different parallel pathways, however, remains inadequately understood
and quantified. SOM production from isoprene photooxidation was studied
under hydroperoxyl-dominant conditions for <5% relative humidity
and at 20 °C in the presence of highly acidic to completely neutralized
sulfate particles. Isoprene photooxidation was separated from SOM
production by using two continuously mixed flow reactors connected
in series and operated at steady state. Two online mass spectrometers
separately sampled the gas and particle phases in the reactor outflow.
The loss of specific gas-phase species as contributors to the production
of SOM was thereby quantified. The produced SOM mass concentration
was directly proportional to the loss of isoprene epoxydiol (IEPOX)
isomers from the gas phase. IEPOX isomers lost from the gas phase
accounted for (46 ± 11)% of the produced SOM mass concentration.
The IEPOX isomers comprised (59 ± 21)% (molecular count) of the
loss of monitored gas-phase species. The implication is that for the
investigated reaction conditions the SOM production pathways tied
to IEPOX isomers accounted for half of the SOM mass concentration