Pan Da, Mauzerall Denise L, Wang Rui, Guo Xuehui, Puchalski Melissa, Guo Yixin, Song Shaojie, Tong Daniel, Sullivan Amy P, Schichtel Bret A, Collett Jeffrey L, Zondlo Mark A
Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ USA.
Department of Atmospheric Science, Colorado State University, Fort Collins, CO USA.
Nat Geosci. 2024;17(7):617-623. doi: 10.1038/s41561-024-01455-9. Epub 2024 Jun 20.
Secondary inorganic aerosols play an important role in air pollution and climate change, and their formation modulates the atmospheric deposition of reactive nitrogen (including oxidized and reduced nitrogen), thus impacting the nitrogen cycle. Large-scale and long-term analyses of secondary inorganic aerosol formation based on model simulations have substantial uncertainties. Here we improve constraints on secondary inorganic aerosol formation using decade-long in situ observations of aerosol composition and gaseous precursors from multiple monitoring networks across the United States. We reveal a shift in the secondary inorganic aerosol formation regime in the rural United States between 2011 and 2020, making rural areas less sensitive to changes in ammonia concentrations and shortening the effective atmospheric lifetime of reduced forms of reactive nitrogen. This leads to potential increases in reactive nitrogen deposition near ammonia emission hotspots, with ecosystem impacts warranting further investigation. Ammonia (NH), a critical but not directly regulated precursor of fine particulate matter in the United States, has been increasingly scrutinized to improve air quality. Our findings, however, show that controlling NH became significantly less effective for mitigating fine particulate matter in the rural United States. We highlight the need for more collocated aerosol and precursor observations for better characterization of secondary inorganic aerosols formation in urban areas.
二次无机气溶胶在空气污染和气候变化中起着重要作用，其形成过程调节着活性氮（包括氧化态氮和还原态氮）的大气沉降，从而影响氮循环。基于模型模拟对二次无机气溶胶形成进行的大规模长期分析存在很大的不确定性。在此，我们利用美国多个监测网络长达十年的气溶胶成分和气态前体原位观测数据，改进了对二次无机气溶胶形成的约束条件。我们揭示了2011年至2020年间美国农村地区二次无机气溶胶形成机制的转变，使得农村地区对氨浓度变化的敏感度降低，并缩短了活性氮还原态的有效大气寿命。这导致氨排放热点附近的活性氮沉降可能增加，其对生态系统的影响值得进一步研究。氨（NH₃）是美国细颗粒物的一种关键但未直接受到监管的前体物，为改善空气质量，人们对其的审查日益严格。然而，我们的研究结果表明，在美国农村地区，控制氨对减轻细颗粒物的效果已显著降低。我们强调需要更多同步的气溶胶和前体物观测数据，以便更好地表征城市地区二次无机气溶胶的形成。
