Comparison of Black and Brown Carbon Emission Factors, Pollutant Ratios and Optical Properties in Prescribed Burn and Wildland Fire Smoke in California

Rebecca A. Sugrue, Farrah Haeri, Chelsea V. Preble, Deep Sengupta, Nathan Kreisberg, Paul Van Rooy, John Battles, JAMES D.A. BUTLER, Coty Jen, Kelley Barsanti, Allen Goldstein, Thomas W. Kirchstetter, Afsara Tasnia, Robert York, Scott Stephens, University of California, Berkeley

     Abstract Number: 608
     Working Group: Carbonaceous Aerosol

Abstract
Climate change and a build-up of excess fuel loads over the previous century are contributing to an increase the frequency and intensity of wildland fires in the western United States. Prescribed burns are a low-cost and effective fuels management practice to ensure healthy and climate resilient forests long employed by indigenous peoples. Wildland fires and prescribed burns alike generate fine particulate matter (PM2.5) and other toxic air pollutants that are climate pollutants and degrade air quality in downwind communities. Black carbon (BC), a component of PM2.5 and a short-lived climate pollutant, was measured on a ground-based utility vehicle platform with a multi-wavelength dual-spot aethalometer and on an aerial-based drone platform with the UC Berkeley low-cost aerosol black carbon detector (ABCD). CO and CO2 were measured alongside BC to calculate fuel-based emission factors during four prescribed burns in a productive mixed conifer forest at the Blodget Forest Research Station. We also measured BC and PM2.5 from aged wildland fire smoke with a distributed network of 24 ABCDs in Richmond, CA during August 2020 and obtained BC, PM2.5 and CO measurements at regulatory sites in the SF Bay Area and Los Angeles for 2018­­‑2020. Brown carbon (BrC) concentrations and the absorption Angstrom exponent (AAE) were determined from BC data measured with a multi-wavelength aethalometer and informed when regulatory sites were impacted by wildfire smoke. For the low-cost distributed network and regulatory sites, the black carbon to fine particulate matter ratio (BC/PM2.5) and BC to CO enhancement ratio (DBC/DCO) attributable to wildland fire smoke were calculated. Emission factors and pollutant ratios measured at the prescribed burns, by the low-cost distributed network, and at regulatory sites will provide more accurate emissions estimates to constrain California’s BC emissions inventory and as inputs to a first-order fire effects model (FOFEM).