Wildfires Fertilize Lake and Landscape

Document Type

Conference Paper

Publisher

American Geophysical Union

Publication Date

12-13-2024

Keywords

wildfire smoke, ash, fertilizer, freshwater fertilization

Abstract

Wildfire smoke is a pervasive phenomenon and a significant source of particulate matter to the atmosphere. In addition to its effects on air quality, wildfire ash can supply nutrients and pollutants to terrestrial and aquatic ecosystems via dry (particulate) and wet (precipitation) deposition. This research aims to quantify smoke influence on the wet deposition of biologically-important nutrients (inorganic nitrogen (N), phosphorus (P), and potassium (K)) to ecosystems across the continental U.S. during three years with contrasting smoke frequency and distribution – 2014, 2020, and 2022. Smoke polygon data from NOAA’s Hazard Mapping System (HMS) Fire and Smoke Product were combined with rainfall and wet deposition data from the National Atmospheric Deposition Program (NADP) to build a geospatial database of smoke-affected wet deposition across the continental U.S. At the more than 230 NADP sites, the mean number of smoke-affected rain days in 2022 was 23, six times and three times higher compared to 2014 (4 days) and 2020 (7 days). Sites in the 75th percentile for smoke-affected rain were concentrated in the Northern Great Plains, Southeastern Plains, and Eastern Temperate Forests. Preliminary data indicate that concentrations of N, P, and K are significantly greater in smoke-affected rain than in non-smoke-affected rain samples. Counts of charcoal particles filtered from a subset of wet deposition samples were weakly but positively related to P and K concentrations. Significant positive relationships were also detected between annual wet deposition of nitrate, ammonium, and P and the total annual number of smoke-affected rain days at the NADP sites. The strength of these relationships was more pronounced in 2022 compared to the other sample years. Our findings suggest that wildfires may fertilize freshwaters and adjacent landscapes.

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