Dilution and photooxidation driven processes explain the evolution of organic aerosol in wildfire plumes

Abstract

Wildfires are an important atmospheric source of primary organic aerosol (POA) and precursors for secondary organic aerosol (SOA) at regional and global scales. However, there are large uncertainties surrounding the...

Phase Behavior and Viscosity in Biomass Burning Organic Aerosol and Climatic Impacts

“…Previous studies have investigated the phase behavior of some types of atmospheric aerosol particles, such as mixtures of secondary organic aerosol with inorganic salts and mixtures of secondary organic aerosol with hydrocarbon-like organic aerosol. − However, the phase behavior of primary BBOA remains understudied and unresolved. Models simulating the microphysics, chemical evolution, concentration, or radiative properties of wildfire smoke typically assume that BBOA comprises only a single phase. ,− On the other hand, Jahn et al identified that some sampled BBOA particles exhibited an organic shell coating an organic core using transmission electron microscopy images, with the caveat that the vacuum conditions required for this type of microscopy may affect the particle morphology. In addition, bulk-phase liquid tar condensates generated from high-temperature wood distillation were reported to have separated into a water-soluble and nonsoluble oily phase, , although it is not known whether phase separation would occur in particles containing this material after equilibration with ambient relative humidity (RH).…”

Emission Factors From Wildfires in the Western US: An Investigation of Burning State, Ground Versus Air, and Diurnal Dependencies During the FIREX‐AQ 2019 Campaign

“…As such, it was best to work with fresh (i.e., near‐source) emissions, but this must be defined first. An assessment of OH concentrations was made during the WE‐CAN field campaign, which also took place in the Western US during the summer of 2018 (Akherati et al., 2022). They found higher‐than‐ambient OH concentrations (3 × 10 6 to 1 × 10 7 molecules cm −3 ) within the wildfire plume that produced rapid oxidation during the first hour of transport, followed by lower‐than‐ambient OH (<10 6 molecules cm −3 ) over the next several hours that produced slower chemical changes.…”

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

“…TOMAS uses a number and mass moment scheme to simulate aerosol processes of coagulation, condensation, evaporation, and nucleation . A detailed description of the SOM-TOMAS model along with the governing equations can be found in previous publications. , Recently, the SOM-TOMAS model was used to study SOA formation from biomass burning emissions and evaporated biofuels in chamber experiments, , from α-pinene in an oxidation flow reactor, inside wildfire plumes, and at a continental rural site …”

“…30 A detailed description of the SOM-TOMAS model along with the governing equations can be found in previous publications. 31,32 Recently, the SOM-TOMAS model was used to study SOA formation from biomass burning emissions and evaporated biofuels in chamber experiments, 31,33 from α-pinene in an oxidation flow reactor, 32 inside wildfire plumes, 34 and at a continental rural site. 65 The SOM-TOMAS is a parameterized model and uses the following five parameters to track the oxidation chemistry of the VOC and its oxidation products that includes both functionalization and fragmentation reactions: (i-iv) p f,1 to p f,4 , mass yields for four functionalized products that add one, two, three, and four oxygen atoms to the carbon backbone, respectively; and (v) m frag , a parameter used to calculate the probability of fragmentation (P frag ) based on the oxygen-tocarbon ratio (O:C) of the model species (P frag = (O:C) m frag ).…”