Pronounced increases in nitrogen emissions and deposition due to the historic 2020 wildfires in the western U.S

Patrick C Campbell; Daniel Tong; Rick Saylor; Yunyao Li; Siqi Ma; Xiaoyang Zhang; Shobha Kondragunta; Fangjun Li

doi:10.1016/j.scitotenv.2022.156130

Pronounced increases in nitrogen emissions and deposition due to the historic 2020 wildfires in the western U.S

Sci Total Environ. 2022 Sep 15:839:156130. doi: 10.1016/j.scitotenv.2022.156130. Epub 2022 May 21.

Authors

Patrick C Campbell¹, Daniel Tong², Rick Saylor³, Yunyao Li⁴, Siqi Ma⁴, Xiaoyang Zhang⁵, Shobha Kondragunta⁶, Fangjun Li⁵

Affiliations

¹ Center for Spatial Information Science and Systems/Cooperative Institute for Satellite Earth System Studies, George Mason University, Fairfax, VA, USA; Office of Air and Radiation, Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD, USA. Electronic address: Patrick.C.Campbell@noaa.gov.
² Center for Spatial Information Science and Systems/Cooperative Institute for Satellite Earth System Studies, George Mason University, Fairfax, VA, USA; Department of Atmospheric, Oceanic and Earth Sciences, George Mason University, Fairfax, VA, USA.
³ Office of Air and Radiation, Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD, USA.
⁴ Department of Atmospheric, Oceanic and Earth Sciences, George Mason University, Fairfax, VA, USA.
⁵ Geospatial Sciences Center of Excellence, Department of Geography & Geospatial Sciences, South Dakota State University, Brookings, SD, USA.
⁶ NOAA Satellite Meteorology and Climatology Division, NOAA Air Resources Laboratory, College Park, MD, USA.

PMID: 35609700
DOI: 10.1016/j.scitotenv.2022.156130

Abstract

Wildfire outbreaks can lead to extreme biomass burning (BB) emissions of both oxidized (e.g., nitrogen oxides; NO_x = NO+NO₂) and reduced form (e.g., ammonia; NH₃) nitrogen (N) compounds. High N emissions are major concerns for air quality, atmospheric deposition, and consequential human and ecosystem health impacts. In this study, we use both satellite-based observations and modeling results to quantify the contribution of BB to the total emissions, and approximate the impact on total N deposition in the western U.S. Our results show that during the 2020 wildfire season of August-October, BB contributes significantly to the total emissions, with a satellite-derived fraction of NH₃ to the total reactive N emissions (median ~ 40%) in the range of aircraft observations. During the peak of the western August Complex Fires in September, BB contributed to ~55% (for the contiguous U.S.) and ~ 83% (for the western U.S.) of the monthly total NO_x and NH₃ emissions. Overall, there is good model performance of the George Mason University-Wildfire Forecasting System (GMU-WFS) used in this work. The extreme BB emissions lead to significant contributions to the total N deposition for different ecosystems in California, with an average August - October 2020 relative increase of ~78% (from 7.1 to 12.6 kg ha^-1 year^-1) in deposition rate to major vegetation types (mixed forests + grasslands/shrublands/savanna) compared to the GMU-WFS simulations without BB emissions. For mixed forest types only, the average N deposition rate increases (from 6.2 to 16.9 kg ha^-1 year^-1) are even larger at ~173%. Such large N deposition due to extreme BB emissions are much (~6-12 times) larger than low-end critical load thresholds for major vegetation types (e.g., forests at 1.5-3 kg ha^-1 year^-1), and thus may result in adverse N deposition effects across larger areas of lichen communities found in California's mixed conifer forests.

Keywords: 2020 U.S. Wildfires; Biomass burning emissions; George Mason University-Wildfire Forecast System; Nitrogen deposition; Nitrogen emissions; WRF-CMAQ model.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
Ecosystem
Humans
Nitrogen / analysis
United States
Wildfires*

Substances

Air Pollutants
Nitrogen