Vapors Are Lost to Walls, Not to Particles on the Wall: Artifact-Corrected Parameters from Chamber Experiments and Implications for Global Secondary Organic Aerosol

Abstract

Atmospheric models of secondary organic aerosol (OA) (SOA) typically rely on parameters derived from environmental chambers. Chambers are subject to experimental artifacts, including losses of (1) particles to the walls (PWL), (2) vapors to the particles on the wall (V2PWL), and (3) vapors to the wall directly (VWL). We present a method for deriving artifactcorrected SOA parameters and translating these to volatility basis set (VBS) parameters for use in chemical transport models (CTMs). Our process involves combining a box model that accounts for chamber artifacts (Statistical Oxidation Model with a TwO-Moment Aerosol Sectional model (SOM-TOMAS)) with a pseudo-atmospheric simulation to develop VBS parameters that are fit across a range of OA mass concentrations. We found that VWL led to the highest percentage change in chamber SOA mass yields (high NO x : 36−680%; low NO x : 55−250%), followed by PWL (high NO x : 8−39%; low NO x : 10−37%), while the effects of V2PWL are negligible. In contrast to earlier work that assumed that V2PWL was a meaningful loss pathway, we show that V2PWL is an unimportant SOA loss pathway and can be ignored when analyzing chamber data. Using our updated VBS parameters, we found that not accounting for VWL may lead surface-level OA to be underestimated by 24% (0.25 μg m −3 ) as a global average or up to 130% (9.0 μg m −3 ) in regions of high biogenic or anthropogenic activity. Finally, we found that accurately accounting for PWL and VWL improves model-measurement agreement for fine mode aerosol mass concentrations (PM 2.5 ) in the GEOS-Chem model.

Primary and Secondary Organic Aerosol Formation from Asphalt Pavements

“…Heating asphalt to the application temperature (red-shaded region in Figure a) produced POA (∼30 μg/m 3 ). After sample injection, the OA concentration declined due to both particle wall loss and the uptake of organic vapors to the chamber walls, which caused the ratio of OA to the seed mass to steadily drop, as shown in Figure a. , During photo-oxidation (blue-shaded region in Figure a), the loss of POA to the chamber wall was countered by substantial SOA formation. Hence, the wall loss-corrected OA concentrations eventually stabilized, with wall losses approximately balancing continued SOA formation.…”

Quantifying the Light-Absorption Properties and Molecular Composition of Brown Carbon Aerosol from Sub-Saharan African Biomass Combustion

“…Furthermore, the presence of moisture on the chamber walls might cause a higher tendency for species to adhere to the wall compared to the dry chamber condition. The latter could lead to potential selective losses of BrC aerosol species or gases , to the chamber walls, affecting the intensive optical absorption characteristics of primary BB aerosols. With photochemical aging, the OA MAC reduction at 370 nm and enhancement at longer wavelengths (Figure b) relate to the photochemical degradation of lignin pyrolysis products and concurrent formation of visible-light-absorbing NACs (Figures and S3).…”

Secondary Organic Aerosol Formation from Volatile Chemical Product Emissions: Model Parameters and Contributions to Anthropogenic Aerosol

“…The SOM-TOMAS model output was used to develop VBS (or VBS SOM ) parameters for VCP OVOCs that theoretically account for the influence of multigenerational aging and some of the important environmental chamber artifacts (i.e., particle and vapor wall losses). This approach was identical to that developed by our group to develop VBS parameters for SOA precursors in a widely used CTM (GEOS-Chem); details can be found in Bilsback et al 43 Briefly, we performed pseudoatmospheric simulations with the SOM-TOMAS model where a trace amount of initial VOC (1 pptv) was oxidized for 48 h (2 days) at three different OA mass concentrations (0.1, 1, and 10 μg m −3 ) and an OH concentration of 1.5 × 10 6 molecules cm −3 . A time step of 10 s was used for these simulations.…”