Particle behavior and water quality response of wildfire ash compared to laboratory heated materials
- 1Department of Civil and Environmental Engineering, Washington State University, Pullman, WA, USA; Department of Civil and Construction Engineering and Management, The University of Texas at Tyler, Tyler, TX, USA; Department of Civil Engineering, Montana State University, Bozeman, MT, USA
- 2Department of Civil and Environmental Engineering, Washington State University, Pullman, WA, USA
- 3Department of Civil Engineering, Montana State University, Bozeman, MT, USA; Corresponding author.
Abstract
Following wildfires, first-flush rainstorms quickly mobilize ash into surface waters, leading to degraded water quality and substantial challenges for drinking water providers. Many studies use laboratory approaches to produce heat-altered materials but lack comparisons to environmental wildfire ashes. In this study, particle behavior and water quality effects from California and Oregon (USA) wildfire ashes and unburned soils were compared to laboratory heated materials (250, 450, and 650 °C) in ash-water mixtures. Environmental wildfire ashes were characterized by color to indicate combustion completeness, with lighter ash color indicating greater combustion temperatures. Solid materials were mixed with three background waters (5 g/L). Prior to settling, wildfire ash turbidity was always greater than that of unburned soils. White ashes and high temperature lab ashes produced the greatest initial turbidities, nearly 10 times the turbidity of unburned materials. After 24 h of settling, turbidity remained elevated for moderate and high temperature ashes, suggesting ash may contain more stable particles, substantiated by the greater observed zeta potential of ashes. Wildfire ashes increased pH to >10 and alkalinity up to 4-fold. Low-moderate temperature wildfire and lab ashes released the greatest organic carbon and nitrogen, whereas white ash, 650 °C ash, and unburned materials released the least. While post-fire water contamination will be governed by rainfall, hydrology, and downstream dilution, these findings suggest that mobilization of highly combusted ash has the greatest potential to increase turbidity, zeta potential, and particle stability, and darker ash has potential to release more organic matter, which together can potentially create compounding challenges for drinking water treatment.
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BibTeX
@article{rodela2026particle,
title = {{Particle behavior and water quality response of wildfire ash compared to laboratory heated materials}},
author = {Mrittika Hasan Rodela and Indranil Chowdhury and Amanda K. Hohner},
journal = {Water Research X},
year = {2026},
month = oct,
doi = {10.1016/j.wroa.2026.100625},
url = {https://doi.org/10.1016/j.wroa.2026.100625},
note = {CC BY},
}
RIS
TY - JOUR
TI - Particle behavior and water quality response of wildfire ash compared to laboratory heated materials
AU - Mrittika Hasan Rodela
AU - Indranil Chowdhury
AU - Amanda K. Hohner
PY - 2026
DA - 2026/10/30
JO - Water Research X
DO - 10.1016/j.wroa.2026.100625
UR - https://doi.org/10.1016/j.wroa.2026.100625
AB - Following wildfires, first-flush rainstorms quickly mobilize ash into surface waters, leading to degraded water quality and substantial challenges for drinking water providers. Many studies use laboratory approaches to produce heat-altered materials but lack comparisons to environmental wildfire ashes. In this study, particle behavior and water quality effects from California and Oregon (USA) wildfire ashes and unburned soils were compared to laboratory heated materials (250, 450, and 650 °C) in ash-water mixtures. Environmental wildfire ashes were characterized by color to indicate combustion completeness, with lighter ash color indicating greater combustion temperatures. Solid materials were mixed with three background waters (5 g/L). Prior to settling, wildfire ash turbidity was always greater than that of unburned soils. White ashes and high temperature lab ashes produced the greatest initial turbidities, nearly 10 times the turbidity of unburned materials. After 24 h of settling, turbidity remained elevated for moderate and high temperature ashes, suggesting ash may contain more stable particles, substantiated by the greater observed zeta potential of ashes. Wildfire ashes increased pH to >10 and alkalinity up to 4-fold. Low-moderate temperature wildfire and lab ashes released the greatest organic carbon and nitrogen, whereas white ash, 650 °C ash, and unburned materials released the least. While post-fire water contamination will be governed by rainfall, hydrology, and downstream dilution, these findings suggest that mobilization of highly combusted ash has the greatest potential to increase turbidity, zeta potential, and particle stability, and darker ash has potential to release more organic matter, which together can potentially create compounding challenges for drinking water treatment.
SN - 2589-9147
ER -