Reactivity of Charcoal-Derived Water Soluble Biomarkers in River Water

Abstract

The purpose of this study is to evaluate the residence time of water-soluble levoglucosan and free lignin-derived phenols, from two different plant charcoals. Dissolved organic matter (DOM) was extracted from honey mesquite and cordgrass charcoal combusted at 250°C. The DOM was incubated with aliquots of filtered water collected from the Trinity River, (TX) for 37 days. We found that the reactivity of levoglucosan was similar to that of freely dissolved lignin-derived phenols in natural water. The results also indicate a shift in lignin aldehydes into acid moieties during the early stages of biodegradation (~2 days for cordgrass and ~6 days for honey mesquite). Based on the molecular nature of levoglucosan (carbohydrate derivative), it was anticipated that it would react quickly and be consumed faster by bacteria than the lignin phenols. The contradiction between the results of the experiment (similar reactivity of both biomarkers) and this initial prediction suggests that anhydrosugars are sufficiently altered to increase their residence time in natural waters to a range similar to more recalcitrant aromatic constituents of DOM. Furthermore, the near complete consumption of these freely dissolved monomers within ~ 3 weeks suggests that combustion-derived water-soluble organics can fuel significant bacterial respiration in natural waters.