Incorporating ¹⁵N into the outputs of SMOKE version 4.6 as the emission input dataset for CMAQ version 5.2.1 for assessing the role emission sources plays in controlling the isotopic composition of NO_x, NO_y, and atmospheric nitrate

Abstract. Nitrogen oxides (NO_x = nitric oxide (NO) + nitrogen dioxides (NO₂)) are important trace gases that affect atmospheric chemistry, air quality and climate. Contemporary development of NO_x emissions inventories is limited by understanding of the roles of vegetation (net NO_x source or net sink), gasoline and diesel in vehicle emissions, and application of NO_x emission control technologies. In this study, we used the nitrogen stable isotope composition of NO_x (δ¹⁵N(NO_x) to resolve the uncertainties in NO_x emission sources, by incorporating ¹⁵N into the US EPA trace gas emission model SMOKE (Sparse Matrix Operator Kernel Emissions) and compared simulated spatiotemporal patterns in NO_x isotopic composition with corresponding atmospheric measurements in West Lafayette, Indiana, USA. The results indicate 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.