TRANSPORT AND FATE OF METALS FOLLOWING THE 2018 WOOLSEY FIRE IN SOUTHERN CALIFORNIA

Climate change is altering global temperatures, precipitation, and wind patterns, resulting in increased potential for extreme fire conditions. As a consequence, wildfires in the Western US have become a serious and persistent environmental threat. We are investigating the long-term impacts of the 2018 Woolsey Fire in California by assessing the spatial and temporal distribution of trace metals throughout the catchment. This fire, which burned almost 100,000 acres, including ~60% of the Malibu Creek Watershed in Los Angeles County, is the eighth most destructive wildfire in California’s history. Wildfires degrade water and sediment quality in multiple ways. The loss of vegetative cover destroys stabilizing root structures, and the intense heat causes the soil to become hydrophobic. These impacts exacerbate surface erosion, mobilizing contaminants such as metals and wildfire-derived compounds, such as polycyclic aromatic hydrocarbons (PAHs). Increased storm intensity and stream discharge associated with climate change further aggravates the hazards of wildfires by enhancing chemical mobilization. While most trace metals contribute to the health of living organisms, they can be toxic or even lethal in excess. Increased contaminant and particulate loading are well documented in burned watersheds; however, these impacts are not well defined in coastal watersheds that link terrestrial and marine ecosystems. This study, therefore, provides an opportunity to assess how changing climate conditions are altering the land-to-sea transport of sediment-bound and dissolved contaminants.