Impacts of wildfire-related chemicals on surface drinking water sources: Status and research gaps

Climate change is driving more severe wildfires, raising urgent concerns about their impact on surface water sources. This critical review, based on 23 studies across 28 watersheds, synthesizes existing knowledge on how wildfires change the concentrations of eight contaminant categories in surface waters: suspended solids and turbidity, nutrients, organic carbon, major ions, trace metals, polycyclic aromatic hydrocarbons (PAHs), persistent organic pollutants (POPs), and wildfire-fighting chemicals (WFFCs). We observed that post-wildfire peak values reached 1142 mg/L for total suspended solids (TSS), ∼145 NTU for turbidity, 6.28 mg/L for nitrate, 31.08 mg/L for TOC, 325 μS/cm for electrical conductivity (EC), and 116 mg/L for trace metals such as zinc, with elevated levels often persisting over five years. Beyond the burned watershed, smoke plumes transport contaminants to distant basins via atmospheric deposition and subsequent runoff. These loads challenge drinking water treatment systems, potentially reducing performance while increasing health risks and operational costs. Although simulation tools exist to assess these risks, they require adaptation to account for wildfire-specific processes like atmospheric deposition and altered hydrology. As a result, further research is required on the persistence and remobilization of wildfire-derived trace metals, PAHs, POPs, and WFFCs, and on treatment performance under wildfire-affected source waters, along with long-term monitoring to supply data that improve modeling.