Abstract
Wild and prescribed fires are important sources of a broad suite of organic compounds collectively termed pyrogenic carbon (PyC). Most PyC compounds have additional sources beyond fire, adding uncertainty to their use as tracers. However, members of the anhydrosugar family of isomeric compounds-levoglucosan, galactosan and mannosan-are generated exclusively by the pyrolysis and combustion of cellulose and hemicellulose. Although anhydrosugars are some of the only unique organic markers for fire, they have not yet seen wide use as tracers in terrestrial or marine research because our understanding of their biogeochemistry and transport through the Earth system is poorly constrained. Anhydrosugars are chemically reactive in all phases (gaseous, aqueous and particulate), molecularly diffusive in semisolid matter, semivolatile, water-soluble, and biodegradable. Their chemical composition also suggests that they sorb to soil mineral surfaces. Together, these characteristics mean that anhydrosugars are not conservative tracers. While these traits have historically been perceived as drawbacks, here we argue that these characteristics present opportunities for new research avenues, including tracking organic matter transport and degradation in multiple environments. We review evidence for anhydrosugar production, degradation and detection in various environments, and use this information to propose new research on PyC and organic matter in the Earth system.