Single-particle transmission electron microscopic analysis of biomass burning aerosol during the FIREX-AQ 2019 campaign

Abstract:

Shapes, mixing states, and compositions of individual biomass-burning aerosol particles collected during the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign in summer 2019 were measured using transmission electron microscopy (TEM). FIREX-AQ aimed to investigate the impact on air quality and climate from wildfires and agricultural burning across the United States. The goal of our TEM analysis is better understanding of particle characteristics from biomass burning the chemical and physical processes occurring during smoke aging and affecting their climate impacts.

Tarballs, a dominant species of spherical organic particles from biomass burning with unique compositions (e.g., N and K) and significance to climate due to their absorption of light, are a focus of our analysis. Findings from the BBOP campaign (Sedlacek et al., 2018) suggested that chemical aging, e.g., increasing of N and O, in the smoke within several hours from the emissions, is a primary formation process of tarballs (Adachi et al., 2019). In the current study, the FIREX-AQ campaign expands the number of samples and aging time scales explored compared to BBOP, allowing reevaluation of the tarball formation processes.

Additional analysis foci from the mission include other types of aerosol particles, such as ash particles that contain Ca and Mg and have aggregate shapes. The results from individual particle analyses help comprehensive particle understanding from biomass burning and data interpretations obtained by other on-line instruments.

References:

Adachi, K. et al., Spherical tarball particles form through rapid chemical and physical changes of organic matter in biomass-burning smoke, Proc Natl Acad Sci U S A, 116, 2019.

Sedlacek III, A. J., et al., Formation and evolution of tar balls from northwestern US wildfires, Atmos. Chem. Phys., 18, 11289–11301, 2018.