Tales from the Smoky Side of the Anthropocene

ARTHUR J. SEDLACEK, Timothy Onasch, Ernie R. Lewis, Brookhaven National Laboratory

     Abstract Number: 505
     Working Group: Aerosol Processes and Properties in Changing Environments in the Anthropocene

Abstract
The Anthropocene—characterized by human activity becoming the dominant force shaping Earth’s ecosystems and geophysical processes—has seen a marked increases in wildfire frequency and intensity. These wildfires are now routinely exerting their weather-altering and health-impacting effects on regional and continental scales. While several studies over the past decade have focused on the rapid changes in the properties of biomass burning aerosols near the source, much less is known on how aerosols age on the regional and continental scales.

We will discuss a framework for elucidating the evolution of biomass burning aerosols wherein the lifecycle of these aerosols can be partitioned into three distinct regimes: (i) near the source (“local”), lasting a few days; (ii) hundreds of kilometers to continental scales (“regional”), lasting a few days; and (iii) thousand kilometers or global scale (“global”) at ages more than a few days. We will present examples of the rapid, and sometimes dramatic, transformations in aerosol properties that occur in the local regime by highlighting the formation and optical properties of tar balls, a special class of light-absorbing organic aerosols (known as brown carbon (BrC) and the rapid increase in coating mass on black carbon (BC) particles. We will then move to the regional and global regimes where dilution, slower atmospheric processes, and episodic cloud processing can further impact the properties of these aging aerosols. We show that thickly-coated BC particles created in the local regime enter a phase of no increase in increase in coating mass, which delineates the regional regime. Following this few-day quiescent period, a slow loss of the coating mass occurs, delineating the global regime. Such dynamism makes a compelling argument that more studies on the regional and global regimes are required to better understand and quantify the complex aging of aerosols over their complete lifecycle.