Molecular Characterization of Organophosphorus Compounds in Wildfire Smoke Using 21-T Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry

Abstract

We present a detailed molecular characterization of organophosphorus compounds in ambient organic aerosol influenced by wildfire smoke. Biomass burning organic aerosol (BBOA) is an important source of phosphorus (P) to surface waters, where even a small imbalance in the P flux can lead to substantial effects on water quality, such as eutrophication, algal blooms, and oxygen depletion. We aimed to exploit the ultrahigh resolving power, mass accuracy, and sensitivity of Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) to explore the molecular composition of an ambient BBOA sample collected downwind of Pacific Northwest wildfires. The 21-T FT-ICR MS yielded 10 533 distinct formulae, which included molecular species comprising C, H, O, and P with or without N, i.e., organophosphorus compounds that have long been quantified in wildfire smoke but have not yet been characterized at the molecular level. The lack of detailed molecular characterization of organophosphorus compounds in BBOA is primarily due to their inherently low concentrations in aerosols and poor ionization efficiency in complex mixtures. We demonstrate that the exceptional sensitivity of the 21-T FT-ICR MS allows qualitative analysis of a previously uncharacterized fraction of BBOA without its selective concentration from the organic matrix, exemplifying the need for ultrahigh-resolution tools for a more detailed and accurate molecular depiction of such complex mixtures.

Tethered balloon system and High-Resolution Mass Spectrometry Reveal Increased Organonitrates Aloft Compared to the Ground Level

“…The displayed insignificance of organosulfates (CHOS and CHNOS) and dominance of both CHO (90 MF; 35% of unique aloft MF) and CHNO (139 MF; 54% of unique aloft MF) contributions to the unique aloft MF is consistent with wildfire influence (Tables S5 and S6). − It is also notable that the unique aloft MF for April 17 (CHO and CHNO molecular groups) have increased O/C ratios (0.59 ± 0.25 to 0.78 ± 0.29 for CHO MF; 0.63 ± 0.22 to 0.73 ± 0.23 for CHNO MF) but overall consistent H/C ratios (1.18 ± 0.32 to 1.14 ± 0.28 for CHO MF; 1.15 ± 0.23 to 1.19 ± 0.23 for CHNO MF) relative to the aloft MF that were common with the ground sample (Figure ). While reported O/C values vary widely across different studies, previous findings have linked increases in O/C ratios to aqueous phase processing, − with some specifically recognizing such an increase due to aqueous transformations within clouds. ,, …”

Case study evaluation of size-resolved molecular composition and phase state of carbonaceous particles in wildfire influenced smoke from the Pacific Northwest

“…Specically, a 21 T FTICR MS system was used for relatively increased condence in the observed molecular formulae due to the elevated mass resolving power. 30,58 It must be noted that the nano-DESI 21 T FTICR MS methodology with the employed data analysis strategy is limited to the interpretation of solubilized organics, is not quantitative, 59 and does not allow for inferences regarding connectivity of atoms (i.e., isomers are not separated). 60 However, similar chemical composition was again noted across all stages for the employed experimental conditions as assessed via the both the weighted signal intensities (Fig.…”

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

“…These are typical molecular compositions reported from ultrahigh-resolution mass spectrometric analyses of BBOA. 13,20,21,23 Most importantly, molecular species with AI mod $ 0.67, C > 17 and O $ 1 atoms were detected, which are likely oxygenated polycyclic aromatic hydrocarbons (O-PAHs); these O-PAHs could be strong chromophores emitted as primary brown carbon from biomass burning. 49 Formulae belonging to additional classes, CH and CHN, were exclusively detected with (−)LDI in all aerosol samples (n = 6-13 CH and 2-13 CHN).…”

“…ESI has long been a method of choice to characterise OA because it is a 'so' ionisation technique that ionises many polar compounds over a wide size range with little to no fragmentation (e.g., [20][21][22][23] ). It has been adapted into (nano-) desorption ESI to minimise sample preparation, where it remains selective for polar, medium to high-molecular-weight species.…”