Yellow Beads and Missing Particles: Trouble Ahead for Filter-Based Absorption Measurements

Particulate emissions from low-temperature biomass burning are dominated by organic matter. Here, we show that such emissions have a liquid, bead-like appearance when collected on fibrous filters, and the number of these beads are far less than expected for solid spherical particles. These shapes are in line with published drop-on-fiber theories for liquids entrained on filaments. A smoldering pine sample is yellowish, with organic carbon over 99% of the total carbon, and chars substantially in thermal-optical analysis (TOA), indicating that such liquid organic particles could affect both absorption measurements and TOA of such samples. Similar colored samples collected in the field from rice-straw burning and cook stove emissions also show a similar liquid appearance.