Chemical Tracers for Wildfires–Analysis of Runoff Surface Water by LC/Q-TOF-MS

A quantitative methodology using high resolution mass spectrometry was developed for the identification of organic compounds derived from wildfires in surface water samples. The methodology involves the use of solid-phase extraction (SPE) followed by detection using liquid chromatography-quadrupole time of flight-mass spectrometry (LC/Q-TOF-MS) for a group of fourteen chemical compounds (pyridine, benzene, naphthalene and biphenyl polycarboxylic acids). All compounds were successfully separated chromatographically using a reversed phase column and they were identified by accurate mass using the deprotonated species and their main fragment ions. The method produced excellent accuracies (>95%) and precisions (3-10%) for all the compounds studied. This methodology was successfully applied to the identification of fourteen compounds in runoff surface waters impacted by wildfires in Colorado. Concentrations of individual compounds ranging from 0.1 to 59.5 µg/L were found in wildfire impacted waters, with totals of ~200 µg/L, thus showing these compounds as chemical tracers of wildfire events at significantly high concentrations. In addition, non-target analysis using chromatography patterns and mass spectrometry identification by MS-MS revealed other polycarboxylic acid isomers were also present in runoff surface water samples. The results obtained herein may serve as the basis for the assesment of wildfire impacts on watersheds general water quality and water treatment, as well as, the potential toxicity of these compounds during water treatment. These data make an important contribution to the nature of dissolved organic matter from wildfire and are useful to better understand the impact of wildfire on water quality and drinking water sources. The concept, workflow, and identity of these aromatic acids and their isomers will be discussed in this presentation, as well as their possible environmental impact on water quality.