Abstract
The partitioning of low- and semi-volatile organic compounds into and out of particles significantly influences secondary organic aerosol formation and evolution. Most atmospheric models treat partitioning as an equilibrium between gas and particle phases, despite few direct measurements and a large range of uncertain mass accommodation coefficients (α). Here we directly measure the dynamic, isothermal partitioning of specific organic compounds using mass spectrometry in a Teflon chamber. Measurements are conducted under dry and humid conditions using seeds of different properties that are atmospherically relevant. α values determined independently from gas- and particle-phase observations are consistent and average 0.88 ± 0.33 for all the studied seeds and probe gases. Our results also imply fast mixing, within ~200 s, between dry α-pinene/O3 SOA and the oxidized compounds. These results indicate that mass transfer limitations in the atmosphere may be less important than some recent studies suggest.
Highlights
The partitioning of low- and semi-volatile organic compounds into and out of particles significantly influences secondary organic aerosol formation and evolution
In our seeded experiments (Supplementary Table 2), as well as the dioctyl sebacate (DOS) seed experiments of Krechmer et al.[31], secondary organic aerosols (SOA) volume formed by the partitioning of these low-volatility and semi-volatile organic compounds (L/SVOCs) usually peaked within 2–3 min of the OH pulse
Since the L/SVOC vapor wall loss timescale for this chamber is ~17 min, the initial SOA formation is dominated by G/P partitioning with little wall effects
Summary
The partitioning of low- and semi-volatile organic compounds into and out of particles significantly influences secondary organic aerosol formation and evolution. Our results imply fast mixing, within ~200 s, between dry α-pinene/O3 SOA and the oxidized compounds These results indicate that mass transfer limitations in the atmosphere may be less important than some recent studies suggest. Krechmer et al determined α for partitioning of oxidized compounds to dioctyl sebacate (DOS) particles in a Teflon chamber by directly measuring and modeling the vapor concentration evolution[31]. They found an average α of 0.7 for L/SVOCs with saturation concentrations ranging from 10−3 to 102 μg m−3. Instant G/P equilibration assumption may become inappropriate if this timescale is relatively long compared with other simulated processes
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
