Brown carbon absorptivity in fresh wildfire smoke: associations with volatility and chemical compound groups

Shetty, Nishit; Liu, Pai; Liang, Yutong; Sumlin, Benjamin J.; Herndon, S. C.; Goldstein, Allen H.; Chakrabarty, Rajan K.

doi:10.1039/d3ea00067b

Cited by 4 publications

(2 citation statements)

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“… 84 , 85 This common characteristic suggests that the processing-level understanding reported in this study may be partially applicable to a wider range of physicochemical processes related to wildfire smoke. In addition, while previous studies have highlighted the importance of low-volatility high-molecular-weight (≥400 Da) chromophores in optical properties of primary combustion BrC, 77 , 86 − 88 this study and our prior work of furan SOA and pyrrole SOA suggest that nighttime oxidation of heterocyclic VOCs may mainly contribute to BrC chromophores with low molecular weight (<400 Da) in wildfire smoke aerosols. 14 , 15 , 39 − 41 Further research is needed to incorporate our findings into climate models to better estimate the RH influence on the radiative effects of wildfire smoke.…”

Section: Atmospheric Implicationssupporting

confidence: 48%

“…This route may partially contribute to the strong BrC light absorption in dry wildfire smoke, as evident from recent field studies. , More importantly, the reduced light absorption and the enhanced oxygenated mass were not only found in the NO 3 -driven secondary BrC formation, but also in the aging processes of biomass-burning aerosols. , This common characteristic suggests that the processing-level understanding reported in this study may be partially applicable to a wider range of physicochemical processes related to wildfire smoke. In addition, while previous studies have highlighted the importance of low-volatility high-molecular-weight (≥400 Da) chromophores in optical properties of primary combustion BrC, ,− this study and our prior work of furan SOA and pyrrole SOA suggest that nighttime oxidation of heterocyclic VOCs may mainly contribute to BrC chromophores with low molecular weight (<400 Da) in wildfire smoke aerosols. ,,− Further research is needed to incorporate our findings into climate models to better estimate the RH influence on the radiative effects of wildfire smoke. Overall, our study demonstrates that environmental conditions such as RH in wildfire smoke can modulate secondary BrC formation and hence regulate the radiative impacts of unabated wildfires in the context of climate change.…”

Section: Atmospheric Implicationsmentioning

confidence: 72%

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Relative Humidity Modulates the Physicochemical Processing of Secondary Brown Carbon Formation from Nighttime Oxidation of Furan and Pyrrole

Chen,

Hamilton,

Ries

et al. 2024

ACS EST Air

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Light-absorbing secondary organic aerosols (SOAs), also known as secondary brown carbon (BrC), are major components of wildfire smoke that can have a significant impact on the climate system; however, how environmental factors such as relative humidity (RH) influence their formation is not fully understood, especially for heterocyclic precursors. We conducted chamber experiments to investigate secondary BrC formation from the nighttime oxidation of furan and pyrrole, two primary heterocyclic precursors in wildfires, in the presence of preexisting particles at RH < 20% and ∼ 50%. Our findings revealed that increasing RH significantly affected the size distribution dynamics of both SOAs, with pyrrole SOA showing a stronger potential to generate ultrafine particles via intensive nucleation processes. Higher RH led to increased mass fractions of oxygenated compounds in both SOAs, suggesting enhanced gas-phase and/ or multiphase oxidation under humid conditions. Moreover, higher RH reduced the mass absorption coefficients of both BrC, contrasting with those from homocyclic precursors, due to the formation of non-absorbing high-molecular-weight oxygenated compounds and the decreasing mass fractions of molecular chromophores. Overall, our findings demonstrate the unique RH dependence of secondary BrC formation from heterocyclic precursors, which may critically modulate the radiative effects of wildfire smoke on climate change.

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Section: Atmospheric Implicationssupporting

confidence: 48%

Section: Atmospheric Implicationsmentioning

confidence: 72%

Relative Humidity Modulates the Physicochemical Processing of Secondary Brown Carbon Formation from Nighttime Oxidation of Furan and Pyrrole

Chen,

Hamilton,

Ries

et al. 2024

ACS EST Air

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Intense formation of secondary ultrafine particles from Amazonian vegetation fires and their invigoration of deep clouds and precipitation

Shrivastava,

Fan,

Zhang

et al. 2024

One Earth

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Anthropogenic Extremely Low Volatility Organics (ELVOCs) Govern the Growth of Molecular Clusters Over the Southern Great Plains During the Springtime

Shrivastava,

Zhang,

Zaveri

et al. 2024

JGR Atmospheres

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New particle formation (NPF) often drives cloud condensation nuclei concentrations and the processes governing nucleation of molecular clusters vary substantially in different regions. The growth of these clusters from ∼2 to >10 nm diameters is often driven by the availability of extremely low volatility organic vapors (ELVOCs). Although the pathways to ELVOC formation from the oxidation of biogenic terpenes are better understood, the mechanistic pathways for ELVOC formation from oxidation of anthropogenic organics are less well understood. We integrate measurements and detailed regional model simulations to understand the processes governing NPF and secondary organic aerosol formation at the Southern Great Plain (SGP) observatory in Oklahoma and compare these with a site within the Bankhead National Forest (BNF) in Alabama, southeast USA. During our two simulated NPF event days, nucleation rates are predicted to be at least an order of magnitude higher at SGP compared to BNF largely due to lower sulfuric acid (H2SO4) concentrations at BNF. Among the different nucleation mechanisms in WRF‐Chem, we find that the dimethylamine (DMA) + H2SO4 nucleation mechanism dominates at SGP. We find that anthropogenic ELVOCs are critical for explaining the growth of particles observed at SGP. Treating organic particles as semisolid, with strong diffusion limitations for organic vapor uptake in the particle phase, brings model predictions into closer agreement with observations. We also simulate two non‐NPF event days observed at the SGP site and show that low‐level clouds reduce photochemical activity with corresponding reductions in H2SO4 and anthropogenic ELVOC concentrations, thereby explaining the lack of NPF.

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Brown carbon absorptivity in fresh wildfire smoke: associations with volatility and chemical compound groups

Abstract: Organic aerosol (OA) emissions from wildfires across the western United States have significant impacts on the climate and air quality. Brown carbon (BrC)—the light-absorbing component of OA—has been at the...

Cited by 4 publications

References 89 publications

Relative Humidity Modulates the Physicochemical Processing of Secondary Brown Carbon Formation from Nighttime Oxidation of Furan and Pyrrole

Relative Humidity Modulates the Physicochemical Processing of Secondary Brown Carbon Formation from Nighttime Oxidation of Furan and Pyrrole

Intense formation of secondary ultrafine particles from Amazonian vegetation fires and their invigoration of deep clouds and precipitation

Anthropogenic Extremely Low Volatility Organics (ELVOCs) Govern the Growth of Molecular Clusters Over the Southern Great Plains During the Springtime

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