Increased levels of atmospheric phosphorus and other nutrients associated with fires in the western United States

Wildfire activity is increasing and linked to climate change effects including rising global temperatures and more frequent drought conditions. Wildfire emissions likely impact human health and sensitive ecosystems, particularly in the western United States where fire frequency and severity have increased dramatically in the past decade. Herein, 15 years (2006-2020) of PM2.5 chemical speciation data were linked with smoke plume analysis to identify airborne nutrients that were elevated on smoke-impacted days. Except for ammonium, all macro- and micro-nutrients analyzed (phosphorus, calcium, potassium, sodium, silicon, copper, aluminum, iron, manganese, magnesium, zinc, nitrate) were elevated on fire days, with some nutrients episodically elevated >10,000% during select fire events. A box model was developed to calculate phosphorus deposition from atmospheric concentrations on smoke days, facilitating a comparison to other fluxes of phosphorus. Air mass trajectory analysis and satellite cyanobacteria measurements suggest fire emissions influence algal activity in lakes up to 65 kilometers downwind from fires. These results suggest potential implications for the emergence of harmful algal blooms, even in alpine lakes with limited upstream agriculture and nutrient inputs.

Impact/Purpose

The frequency and size of wildfires is increasing in the western United States, raising questions about quantifying emissions from fires and investigating downwind smoke effects. In this study, we focused on quantifying aerosolized plant nutrients and subsequent ecosystem effects. We used 15 years of PM2.5 chemical speciation data that were linked to smoke plume analysis to identify chemical species that are elevated on smoke-impacted days. Several case studies were identified in which phosphorus emissions were >50,000% above background levels. Paired with the analysis of air mass trajectories and satellite cyanobacteria measurements, we were able to identify alpine lakes with increased algal activity following deposition of nutrients from wildfire smoke. These results suggest potential ecological implications for mountain lakes and other bodies of water downwind from wildfires. 

Citation

Olson, N., K. Boaggio, B. Rice, S. LeDuc, AND U. Shankar. Increased levels of atmospheric phosphorus and other nutrients associated with fires in the western United States. To be presented at American Association for Aerosol Research annual conference, Raleigh, NC, October 03 - 07, 2022.