Ambient Dust, Entrained Soil and the Toxicity of Wildfire Smoke in a Changing Climate

BROOKE L. HEMMING, Anne E. Barkley, U.S. Environmental Protection Agency

     Abstract Number: 581
     Working Group: Carbonaceous Aerosols

Abstract
The changing intensity and scale of wildfires is a symptom of climate change with significant smoke-related impacts on public health and downwind ecosystems. On-going climate change will continue altering these patterns while at the same time affecting variables that determine the toxicity of the smoke. Among the climate-sensitive variables are those affecting the primary carbon content of smoke particles, the nature and rates of in-plume photochemical oxidation processes, and the altitudes and transit periods of smoke plumes. Climate change-induced impacts include altered fuel bed vegetation species composition and meteorological patterns that control fuel moisture and burning conditions. Climate also influences the entrainment of soil and ambient dust that can change the mix of reactive species in a smoke plume.

The formation and photochemistry of atmospheric brown carbon (BrC) is a major subject of interest given its effect on radiative forcing of the climate system. The photochemical reactions studied and proposed as mechanisms for combustion-produced and photochemically-formed brown carbon lead to oxidized particle-bound species that have clear health implications for exposed human populations. The addition of soil entrained from the fuel bed of a fire and dust present in the atmosphere downwind can provide reactive and/or catalytic surfaces which may amplify the oxidation rates of particle-bound organic carbon species. This presentation will provide an overview of the theoretical climate change impacts on wildfire BrC/soil/dust photochemistry and explore the potential respiratory toxin generation process based on a synthesis of available scientific literature. Suggestions for additional research that can deepen our understanding of the process will be offered. This work is intended to improve understanding of the potential influence of the changing climate on wildfire smoke toxicity for humans and downwind ecosystems, in support of the development effective strategies for climate-adaptive public health and ecosystems protection strategies.