Issue 10, 2023

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

Abstract

Tar balls (TBs) are a major carbonaceous product of wildfires and other biomass-burning events that often exceed soot or other elemental forms of carbon in number and mass. Being a recalcitrant fraction of organic carbon, TBs are capable of long-range atmospheric transport, and thus, exert influence not only in the vicinity of wildfires but also in remote regions. Here, we characterised ambient atmospheric aerosol samples with varying TB number fractions collected downwind of Pacific Northwest wildfires using a 15-Tesla Fourier transform-ion cyclotron resonance mass spectrometer (15-T FT-ICR MS). Relative to non-TB aerosol, we found 2006 and 851 molecular formulae exclusively in TB-rich aerosol using laser desorption ionisation (LDI) of samples directly from an aerosol-loaded substrate and electrospray ionisation (ESI) of ACN-extracted aerosol, respectively. Elemental composition from LDI/15-T FT-ICR MS revealed TBs to be abundant in molecular species of low volatility and high viscosity, providing molecular detail that was consistent with key climate and air quality-related properties of TBs. Our findings demonstrate that the TB-specific molecular composition obtained from (−)LDI/15-T FT-ICR MS not only complements (−)ESI analyses, but provides a more apt reflection of the physical properties of TBs as well. We provide proof-of-concept evidence for the potential value of using LDI/15-T FT-ICR MS in routine OA analyses, specifically smoke samples rich in refractory OA, and improve the representation of OA in atmospheric and climate modelling studies that aim to fully understand its impact and occurrence.

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

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Article information

Article type
Paper
Submitted
10 jun 2023
Accepted
07 set 2023
First published
20 set 2023
This article is Open Access
Creative Commons BY-NC license

Environ. Sci.: Atmos., 2023,3, 1552-1562

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

A. Ijaz, W. Kew, Z. Cheng, S. Mathai, N. N. Lata, L. Kovarik, S. Schum, S. China and L. R. Mazzoleni, Environ. Sci.: Atmos., 2023, 3, 1552 DOI: 10.1039/D3EA00085K

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