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1. Top-Down Estimates of NO x and CO Emissions From Washington, D.C.-Baltimore During the WINTER Campaign

   https://doi.org/10.1029/2018JD028539  

   Salmon, O. E. ; Shepson, P. B. ; Ren, X. ; He, H. ; Hall, D. L. ; Dickerson, R. R. ; Stirm, B. H. ; Brown, S. S. ; Fibiger, D. L. ; McDuffie, E. E. ; et al ( July 2018 , Journal of Geophysical Research: Atmospheres)
2. Top-Down Constraints on Anthropogenic CO 2 Emissions Within an Agricultural-Urban Landscape

   https://doi.org/10.1029/2017JD027881  

   Hu, Cheng ; Griffis, Timothy J. ; Lee, Xuhui ; Millet, Dylan B. ; Chen, Zichong ; Baker, John M. ; Xiao, Ke ( May 2018 , Journal of Geophysical Research: Atmospheres)
3. The challenge of reconciling bottom-up agricultural methane emissions inventories with top-down measurements

   https://doi.org/10.1016/j.agrformet.2017.09.003  

   Desjardins, R.L. ; Worth, D.E. ; Pattey, E. ; VanderZaag, A. ; Srinivasan, R. ; Mauder, M. ; Worthy, D. ; Sweeney, C. ; Metzger, S. ( January 2018 , Agricultural and Forest Meteorology)
4. Magnitude and Uncertainty of Nitrous Oxide Emissions From North America Based on Bottom‐Up and Top‐Down Approaches: Informing Future Research and National Inventories

   https://doi.org/10.1029/2021GL095264  

   Xu, R. ; Tian, H. ; Pan, N. ; Thompson, R. L. ; Canadell, J. G. ; Davidson, E. A. ; Nevison, C. ; Winiwarter, W. ; Shi, H. ; Pan, S. ; et al ( November 2021 , Geophysical Research Letters)

   We synthesized N₂O emissions over North America using 17 bottom‐up (BU) estimates from 1980–2016 and five top‐down (TD) estimates from 1998 to 2016. The BU‐based total emission shows a slight increase owing to U.S. agriculture, while no consistent trend is shown in TD estimates. During 2007–2016, North American N₂O emissions are estimated at 1.7 (1.0–3.0) Tg N yr⁻¹(BU) and 1.3 (0.9–1.5) Tg N yr⁻¹(TD). Anthropogenic emissions were twice as large as natural fluxes from soil and water. Direct agricultural and industrial activities accounted for 68% of total anthropogenic emissions, 71% of which was contributed by the U.S. Our estimates of U.S. agricultural emissions are comparable to the EPA greenhouse gas (GHG) inventory, which includes estimates from IPCC tier 1 (emission factor) and tier 3 (process‐based modeling) approaches. Conversely, our estimated agricultural emissions for Canada and Mexico are twice as large as the respective national GHG inventories.

    

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5. Formation of condensable organic vapors from anthropogenic and biogenic volatile organic compounds (VOCs) is strongly perturbed by NO_<i>x</i> in eastern China

   https://doi.org/10.5194/acp-21-14789-2021  

   Liu, Yuliang ; Nie, Wei ; Li, Yuanyuan ; Ge, Dafeng ; Liu, Chong ; Xu, Zhengning ; Chen, Liangduo ; Wang, Tianyi ; Wang, Lei ; Sun, Peng ; et al ( January 2021 , Atmospheric Chemistry and Physics)

   Abstract. Oxygenated organic molecules (OOMs) are the crucial intermediates linkingvolatile organic compounds (VOCs) to secondary organic aerosols (SOAs) in theatmosphere, but comprehensive understanding of the characteristics of OOMsand their formation from VOCs is still missing. Ambient observations ofOOMs using recently developed mass spectrometry techniques are stilllimited, especially in polluted urban atmospheres where VOCs and oxidants areextremely variable and complex. Here, we investigate OOMs, measured by anitrate-ion-based chemical ionization mass spectrometer at Nanjing ineastern China, through performing positive matrix factorization on binnedmass spectra (binPMF). The binPMF analysis reveals three factors aboutanthropogenic VOC (AVOC) daytime chemistry, three isoprene-relatedfactors, three factors about biogenic VOC (BVOC) nighttime chemistry, andthree factors about nitrated phenols. All factors are influenced by NOxin different ways and to different extents. Over 1000 non-nitro moleculeshave been identified and then reconstructed from the selected solution ofbinPMF, and about 72 % of the total signals are contributed bynitrogen-containing OOMs, mostly regarded as organic nitrates formed throughperoxy radicals terminated by nitric oxide or nitrate-radical-initiatedoxidations. Moreover, multi-nitrates account for about 24 % of the totalsignals, indicating the significant presence of multiple generations,especially for isoprene (e.g., C5H10O8N2 andC5H9O10N3). Additionally, the distribution of OOMconcentration on the carbon number confirms their precursors are driven by AVOCsmixed with enhanced BVOCs during summer. Our results highlight the decisiverole of NOx in OOM formation in densely populated areas, and we encouragemore studies on the dramatic interactions between anthropogenic and biogenicemissions. 

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