CHARCOAL CHEMISTRY: DEVELOPING A PROXY FOR PALEOFIRE REGIMES

Wildfires have been a part of Earth’s history ever since plants developed on land and have affected global biogeochemical cycling and ecosystem evolution processes ever since. The only solid residuum remaining from these past fires (paleowildfires) is partially combusted organic matter called charcoal. This residuum records the various aspects of the paleowildfire regime (fuel consumption, seasonality, frequency, fire severity and fire intensity) that can help us understand past climate, vegetation, atmospheric concentrations, etc. Although poorly understood and unquantified for past fires, the fire intensity aspect, described as the amount of heat energy produced during the fire, may be directly recorded in the charcoal chemistry. ¹³C NMR has been used by many workers to study the aromaticity of charcoal in the modern at various temperatures (McBeath et al., 2011), but no proxy for the past has been developed. We have developed a proxy for paleowildfires temperatures to describe fire intensity by comparing the aromatic ring cluster size in charcoals to known charcoal temperatures. A calibration of this proxy at the Waco Wetland in Waco, Texas indicates ring cluster size has a significant correlation to local cattail and willow charcoal specimens. These results may allow for a better understanding of past conditions during fires and better predict the effects and probability of various fires in the future.