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.
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.
Sci Total Environ. 2022 Sep 15;839:156130. doi: 10.1016/j.scitotenv.2022.156130. Epub 2022 May 21.
Wildfire outbreaks can lead to extreme biomass burning (BB) emissions of both oxidized (e.g., nitrogen oxides; NO = NO+NO) and reduced form (e.g., ammonia; NH) 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 NH 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 and NH 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 year) 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 year) 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 year), and thus may result in adverse N deposition effects across larger areas of lichen communities found in California's mixed conifer forests.
野火爆发会导致大量的生物质燃烧（BB）排放氧化态（如氮氧化物；NO = NO+NO）和还原态（如氨；NH）氮（N）化合物。高氮排放量是空气质量、大气沉积以及由此对人类和生态系统健康影响的主要关注点。在本研究中，我们同时使用卫星观测和建模结果来量化 BB 对总排放量的贡献，并估算其对美国西部总氮沉积的影响。研究结果表明，在 2020 年 8 月至 10 月的野火季节，BB 对总排放量的贡献显著，卫星观测到的 NH 与总反应性 N 排放量的比例（中值40%）在飞机观测范围内。在 9 月西部 8 月综合大火的高峰期，BB 对美国西部和美国西部的每月总 NO 和 NH 排放量的贡献分别约为55%和83%。总的来说，本工作中使用的乔治梅森大学野火预测系统（GMU-WFS）具有良好的模型性能。极端的 BB 排放导致了加利福尼亚不同生态系统总氮沉积的显著增加，与没有 BB 排放的 GMU-WFS 模拟相比，2020 年 8 月至 10 月的总氮沉积率平均相对增加了78%（从 7.1 到 12.6 kg ha year），主要植被类型（混合林+草地/灌丛/稀树草原）。仅对于混合林类型，氮沉积率的平均增加（从 6.2 到 16.9 kg ha year）甚至更大，约为~173%。由于极端 BB 排放导致的大量氮沉积，远大于主要植被类型（如森林为 1.5-3 kg ha year）的低端临界负荷阈值，因此可能会导致加利福尼亚混合针叶林的地衣群落的更大面积的不利氮沉积效应。
