Morphology and mixing state of individual freshly emitted wildfire carbonaceous particles

Biomass burning is one of the largest sources of carbonaceous aerosols in the atmosphere, significantly affecting earth's radiation budget and climate. Tar balls, abundant in biomass burning smoke, absorb sunlight and have highly variable optical properties, typically not accounted for in climate models. Here we analyse single biomass burning particles from the Las Conchas fire (New Mexico, 2011) using electron microscopy. We show that the relative abundance of tar balls (80%) is 10 times greater than soot particles (8%). We also report two distinct types of tar balls; one less oxidized than the other. Furthermore, the mixing of soot particles with other material affects their optical, chemical and physical properties. We quantify the morphology of soot particles and classify them into four categories: similar to 50% are embedded (heavily coated), similar to 34% are partly coated, similar to 12% have inclusions and similar to 4% are bare. Inclusion of these observations should improve climate model performances.