Molecular and physical composition of tar balls in wildfire smoke: an investigation with complementary ionisation methods and 15-Tesla FT-ICR mass spectrometry

Ijaz, Amna; Kew, William; Cheng, Zezhen; Mathai, Susan; Lata, Nurun Nahar; Kovarik, Libor; Schum, Simeon; China, Swarup; Mazzoleni, Lynn R.

doi:10.1039/d3ea00085k

Cited by 3 publications

(3 citation statements)

References 55 publications

(128 reference statements)

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“…, not commonly detected across all days) are shaded grey. Given the untargeted nature of this study and consequent lack of quantitative information, presence/absence of MFs are used to compare molecular coverage between days as similarly done in previous atmospheric studies with mass spectrometry application. ,,, While this strategy does not reveal what is occurring wholistically during an individual sampling event, it highlights the distinctive characteristics of that event relative to the rest of the sampling period. Here, only 291 MFs (13% by number) were found to be common across all daytime samples, indicating a high variability of MFs across all sampling days.…”

Section: Resultsmentioning

confidence: 99%

Chemical Insights into the Molecular Composition of Organic Aerosols in the Urban Region of Houston, Texas

Gautam,

Vandergrift,

Lata

et al. 2024

ACS EST Air

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Molecular functional groups, such as organosulfates (CHOS) and organonitrates (CHNO) are important tracers for field observations of secondary organic aerosols (SOA). While CHOS and CHNO are prevalent in the atmosphere, there is a lack of knowledge regarding daily and day- and night-time variations in these species in the urban atmosphere. Meteorological factors such as wind speed/direction, relative humidity (RH), and temperature can influence the formation of CHOS/CHNO. To investigate these trends, we utilized multimodal chemical imaging and advanced high resolution mass spectrometry techniques to acquire particle speciation and molecular formulas (MFs) associated with day and night sampling periods. Back trajectory analyses revealed the oceanic influence of southern wind airmasses in later June sampling periods with organic fractions <10%. Conversely, northern winds in early June sampling periods contributed to the episodic emergence of extremely low volatile organics (ELVOCs) and organic factions up to 41%. The observed unique MFs to June 3 (223 MFs) and to June 4 (144 MFs) were largely found to be of biogenic rather than anthropogenic origin. Our findings reveal episodic prevalence and temporal distribution of SOA constituents across the urban region of Houston, Texas.

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Section: Resultsmentioning

confidence: 99%

Chemical Insights into the Molecular Composition of Organic Aerosols in the Urban Region of Houston, Texas

Gautam,

Vandergrift,

Lata

et al. 2024

ACS EST Air

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“…[43][44][45] To address these limitations, ionization methods capable of achieving direct detection of samples have been proposed. [46][47][48] This study employs a direct LDI method that eliminates the need for SPE and enables a straightforward in situ aerosol sample detection directly on the quartz fiber filter. In brief, aerosol samples were extracted on clean, polluted, and dusty days and were analyzed using ESI and LDI and further compared with an in situ LDI approach, which measured directly on the aerosol filter (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…The competitive nature of ESI causes acidic oxygen‐containing compounds to inhibit the ionization of other less‐polar compounds and leads to an overestimation of the oxygen‐rich and sulfur‐containing organics in the samples, deviating from the actual abundances 43–45 . To address these limitations, ionization methods capable of achieving direct detection of samples have been proposed 46–48 . This study employs a direct LDI method that eliminates the need for SPE and enables a straightforward in situ aerosol sample detection directly on the quartz fiber filter.…”

Section: Introductionmentioning

confidence: 99%

Selective molecular characterization of organic aerosols using in situ laser desorption ionization mass spectrometry

Yuan,

Qi,

et al. 2024

Rapid Comm Mass Spectrometry

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RationaleThe sources and chemical compositions of organic aerosol (OA) exert a significant influence on both regional and global atmospheric conditions, thereby having far‐reaching implications on environmental chemistry. However, existing mass spectrometry (MS) methods have limitations in characterizing the detailed composition of OA due to selective ionization as well as fractionation during cold‐water extraction and solid‐phase extraction (SPE).MethodsA comprehensive MS study was conducted using aerosol samples collected on dusty, clean, and polluted days. To supplement the data obtained from electrospray ionization (ESI), a strategy for analyzing OAs collected using the quartz fiber filter directly utilizing laser desorption ionization (LDI) was employed. Additionally, the ESI method was conducted to explore suitable approaches for determining various OA compositions from samples collected on dusty, clean, and polluted days.ResultsIn situ LDI has the advantages of significantly reducing the sample volume, simplifying sample preparation, and overcoming the problem of overestimating sulfur‐containing compounds usually encountered in ESI. It is suitable for the characterization of highly unsaturated and hydrophobic aerosols, such as brown carbon‐type compounds with low volatility and high stability, which is supplementary to ESI.ConclusionsCompared with other ionization methods, in situ LDI helps provide a complementary description of the molecular compositions of OAs, especially for analyzing OAs in polluted day samples. This method may contribute to a more comprehensive MS analysis of the elusive compositions and sources of OA in the atmosphere.

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Enhanced light absorption for solid-state brown carbon from wildfires due to organic and water coatings

Cheng,

Shrivastava,

Ijaz

et al. 2024

Nat Commun

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Wildfires emit solid-state strongly absorptive brown carbon (solid S-BrC, commonly known as tar ball), critical to Earth’s radiation budget and climate, but their highly variable light absorption properties are typically not accounted for in climate models. Here, we show that from a Pacific Northwest wildfire, over 90% of particles are solid S-BrC with a mean refractive index of 1.49 + 0.056i at 550 nm. Model sensitivity studies show refractive index variation can cause a ~200% difference in regional absorption aerosol optical depth. We show that ~50% of solid S-BrC particles from this sample uptake water above 97% relative humidity. We hypothesize these results from a hygroscopic organic coating, potentially facilitating solid S-BrC as nuclei for cloud droplets. This water uptake doubles absorption at 550 nm and the organic coating on solid S-BrC can lead to even higher absorption enhancements than water. Incorporating solid S-BrC and water interactions should improve Earth’s radiation budget predictions.

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Molecular and physical composition of tar balls in wildfire smoke: an investigation with complementary ionisation methods and 15-Tesla FT-ICR mass spectrometry

Abstract: Laser desorption ionisation, coupled with ultrahigh-resolution mass spectrometry, provides an apt reflection of the physical properties of tar balls in wildfire smoke.

Cited by 3 publications

References 55 publications

Chemical Insights into the Molecular Composition of Organic Aerosols in the Urban Region of Houston, Texas

Chemical Insights into the Molecular Composition of Organic Aerosols in the Urban Region of Houston, Texas

Selective molecular characterization of organic aerosols using in situ laser desorption ionization mass spectrometry

Enhanced light absorption for solid-state brown carbon from wildfires due to organic and water coatings

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