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Title: Modeling of Gas-Wall Partitioning of Organic Compounds Using a Quantitative Structure-Activity Relationship
Abstract. This study streamlines modeling of the gas–wall process (GWP) of semivolatile organic compounds (SVOC) by predicting gas–wall equilibrium partitioning constant (𝐾𝑤,𝑖 ) and accommodation coefficient (α𝑤,𝑖) of SVOC(i) using a quantitative structure–activity relationship. PaDEL-Descriptor, software that calculates molecular descriptors, is employed to obtain physicochemical parameters (i.e., hydrogen bond acidity (𝐻𝑑,𝑖), hydrogen bond basicity (𝐻𝑎,𝑖), dipolarity/polarizability (𝑆𝑖), and polarizability (α𝑖)) of SVOC(i). For the prediction of 𝐾𝑤,𝑖, activity coefficients (γw,i) of SVOC(i) to the chamber wall are semiempirically predicted using chamber data in the form of a polynomial equation coupled with the physicochemical parameters. 𝛾𝑤,𝑖 of various SVOCs differ in functionalities and molecular sizes ranging from 100 to 104. We conclude that the estimation of 𝛾𝑤,𝑖 is essential to improve the prediction of 𝐾𝑤,𝑖. To predict the impact of relative humidity (RH) on GWP, each coefficient in the polynomial equation for ln(𝐾𝑤,𝑖) was correlated to RH. Increasing RH enhanced GWP significantly for all polar SVOCs. For example, the predicted 𝐾𝑤,𝑖 of 1-heptanoic acid increased more than three times (from 0.58 to 1.96) by increasing RH from 0.4 to 0.75 due to the reduction in 𝛾𝑤,𝑖. The characteristic time for GWP are estimated using 𝐾𝑤,𝑖 and α𝑤,𝑖 to evaluate the effect of GWP on secondary organic aerosol (SOA) mass. It might be significant in the absence of inorganic aerosol, but insignificant in the presence of electrolytic salts, where aqueous reactions dominate SOA growth.  more » « less
Award ID(s):
1923651
PAR ID:
10278975
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Atmospheric chemistry and physics discussion
ISSN:
1680-7375
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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