Carbonaceous Aerosol Fingerprint from Wildfires in California between 2018 and 2022 Using an Advanced Total Carbon - Black Carbon (TC-BC) Method

MATIC IVANČIČ, Asta Gregorič, Gašper Lavrič, Bálint Alföldy, Irena Ježek, Sina Hasheminassab, Payam Pakbin, Faraz Ahangar, Mohammad Sowlat, Steven Boddeker, Jack Connor, Charity Garland, Jonathan P. Bower, Martin Rigler, Aerosol d.o.o.

     Abstract Number: 10
     Working Group: Carbonaceous Aerosol

Abstract
In recent years, the intensity and frequency of wildfires have noticeably increased in California, mainly as a consequence of climate-related changes in temperature and precipitation patterns. Wildfires are an important source of carbonaceous aerosols (CA) that strongly impact public health on both local and regional scales, and climate change, on a global scale. While it is demonstrated that different CA components may cause a multitude of health impacts, their influence on climate change is not yet fully understood - it not only absorbs light but also scatters it. Therefore, special attention must be paid to CA's apportionment into different components and their possible sources and formation mechanisms. In this study, we used the Carbonaceous Aerosol Speciation System (CASS, Aerosol d.o.o., Slovenia, EU), comprised of two instruments, a Total Carbon Analyzer TCA08 (Rigler et al., 2020) in tandem with an Aethalometer AE33 (Drinovec et al., 2015), for high-time-resolution measurements of total carbon (TC) and black carbon (BC). By integrating different numerical algorithms to high-time-resolution measurements of CASS (i.e., Aethalometer model, EC tracer model, BrC model), we introduce an advanced method to apportion CA into six components based on their optical absorption properties and their primary or secondary origins: CA = BC_ff + BC_bb + POA_BrC + POA_non-abs + SOA_BrC + SOA_non-abs, where BC_ff and BC_bb represent fossil fuel and biomass burning related BC components, POA_BrC and SOA_BrC are the primary emitted and secondarily formed light-absorbing organic aerosols, and POA_non-abs and SOA_non-abs are non-light-absorbing aerosols.

We analyzed the carbonaceous aerosol fingerprints of selected major wildfires between 2018 and 2022 at three stations in California: Berkeley, Los Angeles, and Riverside. First, we used brown carbon (BrC) as a marker for wildfire plumes. The results indicated that light absorption on BrC can increase fractional contribution to the light absorption at 370 nm to more than 50%. Then, we compared the CA components from the selected wildfires to those of the Campfire, the deadliest and most destructive wildfire in California history.