Nanoparticulate Wood Treatments Contribute to the Aquatic Toxicity of Simulated Urban Wildfire Ashes

Wildland-urban interface fires often burn near important water resources. The hazard of contaminant emissions from these fires to aquatic biological systems remains incompletely described. To define this hazard further, this study uses a laboratory simulation approach to produce consistent synthetic wildland and urban mixture ashes. These ashes are characterized through ecotoxicological assays, inductively coupled plasma mass spectrometry (ICP-MS), and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). Within the ecotoxicology screen, produced urban ash leachates induce a greater toxic response to the microalgae Raphidocelis subcapitata, while the crustacean Daphnia magna exhibited greater immobilization from synthetic wildland ash. No substantial toxicity was observed in either the activated sludge inhibition test or the seedling germination test, suggesting that ecotoxicological effects from wildfire runoff may be highly species specific. When characterizing the ashes, ICP-MS and SEM-EDS reveal that nanoparticulate copper from pressure-treated wood likely contribute to growth inhibition in Raphidocelis subcapitata. Linking a potential specific toxic component may inform future ash management and household material selection.