New Mexico Geological Society Annual Spring Meeting — Abstracts

Post-wildfire debris flows and flooding deliver high loads of sediment and pyrogenic black carbon (PyC) to downstream waterways. Generated by incomplete combustion of organic matter, PyC in the form of soot and char is transported and re-deposited throughout the watershed. Due to the effects of PyC on water quality, its potential to sequester contaminants and its role in storing carbon over short and long timescales, the accumulation of PyC is a multi-faceted and dynamic issue for ecosystems and human populations. The impacts of two recent wildfires in Northern New Mexico are studied with the goal of understanding the fluxes and residence times of PyC in post-wildfire, semi-arid mountainous watersheds. Employing burn severity maps and geospatial data, three sites were selected to collect soil and water samples to characterize PyC: a control, an area impacted by the 2011 burn, and an area impacted by the 2013 burn. In this study, PyC is treated as both a particulate that is transported throughout the watershed, and as a solute that is dissolved and degraded in surface and groundwater. Two black carbon quantification methods are employed: The chemo-thermal oxidation (CTO-375) method to distinguish between soot and char, and the benzene polycarboxylic acids (BPCA) method to quantify the total concentrations of PyC throughout the watershed and to compare concentrations between different geomorphic features and between control and burn sites. Preliminary data from the CTO-375 method shows comparable soot concentrations in the control, 2011, and 2013 burn indicating that the soot is more recalcitrant than char and remains in the watershed long after a wildfire. This data also suggests that the fluxes of black carbon over short time scales are composed mainly of char.