Up in Smoke: Most Aerosolized Fe From Biomass Burning Does Not Derive From Foliage

Iron (Fe) is a limiting micronutrient in many marine ecosystems. The lack of sufficient Fe can stunt marine productivity and limit carbon sequestration from the atmosphere to the ocean. Recent studies suggest that biomass burning represents an important Fe source to the marine environment because pyrogenic particles have enhanced solubility after atmospheric processing. We examined foliage representative of four distinct biomes subject to frequent burning events, including boreal/temporal forests, humid tropical, arid tropical, and grassland. We burned these samples in the absence of soil to isolate the Fe from the fine particle (PM_2.5) fraction that is derived directly from the burning foliage. We find that <1.5% of the Fe in plant matter is aerosolized throughout the burn in the fine fraction. We estimate that between 2% and 9% of the Fe released from biomass burning can be attributed to the fine fraction of the foliage itself, and <50% from the foliage overall. Most of the Fe aerosolized during biomass burning is accounted for by soil-suspended particles.