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- Title
Assessing the roles emission sources and atmospheric processes play in simulating δ15N of atmospheric NOx and NO3- using CMAQ (version 5.2.1) and SMOKE (version 4.6).
- Authors
Fang, Huan; Michalski, Greg
- Abstract
Nitrogen oxides (NO x= nitric oxide (NO) + nitrogen dioxide (NO 2)) are important trace gases that affect atmospheric chemistry, air quality, and climate. Contemporary development of NO x emissions inventories is limited by the understanding of the roles of vegetation (net NO x source or net sink), vehicle emissions from gasoline- and diesel-powered vehicles, the application of NO x emission control technologies, and accurate verification techniques. The nitrogen stable isotope composition (δ15 N) of NO x is an effective tool to evaluate the accuracy of the NO x emission inventories, which are based on different assumptions. In this study, we traced the changes in δ15 N values of NO x along the "journey" of atmospheric NO x , driven by atmospheric processes after different sources emit NO x into the atmosphere. The 15 N was incorporated into the emission input dataset, generated from the US EPA trace gas emission model SMOKE (Sparse Matrix Operator Kernel Emissions). Then the 15 N-incorporated emission input dataset was used to run the CMAQ (Community Multiscale Air Quality) modeling system. By enhancing NO x deposition, we simulated the expected δ15 N of NO 3- , assuming no isotope fractionation during chemical conversion or deposition. The simulated spatiotemporal patterns in NO x isotopic composition for both SMOKE outputs (simulations under the "emission only" scenario) and CMAQ outputs (simulations under the "emission + transport + enhanced NO x loss" scenario) were compared with corresponding measurements in West Lafayette, Indiana, USA. The simulations under the emission + transport + enhanced NO x loss scenario were also compared to δ15 N of NO 3- at NADP (National Atmospheric Deposition Program) sites. The results indicate the potential underestimation of emissions from soil, livestock waste, off-road vehicles, and natural-gas power plants and the potential overestimation of emissions from on-road vehicles and coal-fired power plants, if only considering the difference in NO x isotopic composition for different emission sources. After considering the mixing, dispersion, transport, and deposition of NO x emission from different sources, the estimation of atmospheric δ15 N(NO x) shows better agreement (by ∼ 3 ‰) with observations.
- Subjects
WEST Lafayette (Ind.); CATALYTIC reduction; ANIMAL waste; TRACE gases; EMISSION inventories; ATMOSPHERIC chemistry; ATMOSPHERIC deposition
- Publication
Geoscientific Model Development, 2022, Vol 15, Issue 10, p4239
- ISSN
1991-959X
- Publication type
Article
- DOI
10.5194/gmd-15-4239-2022