Surface runoff from wildfire-affected areas carries ash, black carbon particulates, and pollutants to downgradient surface waters, potentially negatively affecting ecosystems and water quality. Yet, the factors that affect the surface water quality or the extent to which water quality deteriorates after a wildfire is unclear. We analyzed 43 studies from worldwide to evaluate how the burned area, surface water flow rates, and sampling time affect the peak concentration of different types of pollutants. Results reveal that contaminant concentration in surface waters after a wildfire can increase by two orders of magnitude, but the peak concentration and its arrival time depend on pollutant type. Increases in wildfire burned area disproportionally increase total suspended solids (TSS) concentration in downstream surface waters. Conversely, increases in surface water flow up to 10 m<sup>3</sup> s<sup>-1 </sup>increase TSS concentration and further increases in flow decrease in TSS concentration potentially due to dilution or exhaustion of TSS source. The peak concentration for suspended solids and nutrients appears immediately after a wildfire, whereas the peak for heavy metals such as Cu, Pb, and Zn delayed by a year or longer, indicating the slow dissolution of heavy metals from fire-affected areas or debris. Polyaromatic hydrocarbon peaked within a year after wildfire but the peaks did not exceed EPA limits. Collectively, this analysis reveals that post-wildfire risk to downstream aquatic systems is influenced by wildfire burn area, flow rate, and pollutant type. The results could inform management efforts to protect downstream areas and their ecosystem functions.

Wildfire impacts on surface water quality: Effects of the burned area, flow rate, and sampling time

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.