5 Contaminant Transport and Fate in Aquatic Systems

Wednesday, 12 May 2021
8:30 AM - 10:45 AM
JohnNLouie.com Room

PERSISTENCE AND TRANSPORT MECHANISMS OF WILDFIRE-RELATED POLYCYCLIC AROMATIC HYDROCARBONS IN A SOUTHERN CALIFORNIA COASTAL WATERSHED

Paper number: 5-4
Program: Theme Sessions
Time: 9:30 AM – 9:50 AM

Authors

  • Michael Kushner Presenting Author
    California State University, Northridge Geological Sciences, Northridge, CA
  • Christian L. Hoover
    California State University, Northridge, Northridge, CA
  • Kyle H. Ikeda
    California State University, Northridge Geological Sciences, Northridge, CA
  • Greg Jesmok
    California State University, Northridge Geological Sciences, Northridge, CA
  • Alfredo Estrada
    California State University, Northridge Geological Sciences, Northridge, CA
  • Priya Ganguli
    California State University, Northridge Geological Sciences, Northridge, CA
  • Scott Hauswirth
    California State University, Northridge Geological Sciences, Northridge, CA

Abstract

As climate change causes wildfires to become more numerous and destructive, it is necessary to understand the impacts they have on burned watersheds and the fate of wildfire-produced contaminants. Here, we focus on wildfire-associated water quality impairment by assessing the generation of polycyclic aromatic hydrocarbons (PAHs), a class of organic contaminants with carcinogenic, mutagenic, and ecotoxic properties. We investigated PAH impacts associated with the 2018 Woolsey Fire, which burned over half of the Malibu Creek Watershed near Los Angeles, California. We collected soil and water samples periodically and during rain events over three years following the fire. Sampling sites were distributed throughout the watershed to incorporate all major tributaries of Malibu Creek, and to capture varying topography, geology, land use, and fire intensity. The PAH concentrations found exceeded EPA Ambient Water Quality Criteria, primarily during rain events, through the second wet season after the fire. Using molecular ratio approaches, the PAHs detected in water samples were directly linked to burned soil. Elevated PAH concentrations were linked with suspended particulate matter, which was in turn directly related to stream discharge and precipitation intensity. Significant geographic variability was observed during the second wet season, suggesting topography, burn intensity, and other factors play a role in post-fire recovery and the persistence of fire-derived PAHs in the watershed. We investigated the contribution of these factors through a combination of long-term soil and water sampling, assessment of suspended particulate material, analysis of the variation and evolution of PAH compound distributions, and evaluation of geographic controls. Results suggest that a combination of multiple geographic factors contribute to the observed data. Understanding these complex mechanisms is imperative to predicting long-term wildfire impacts on water quality in a variety of settings.

Geological Society of America Abstracts with Programs. Vol. 53, No. 4

doi: 10.1130/abs/2021CD-363330

© Copyright 2021 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.