Urban-scale analysis of nitrogen deposition in Japan: Validation of chemical transport modeling and the sensitivity of anthropogenic nitrogen emissions to dry and wet depositions

Abstract

Nitrogen (N) deposition has been considered as one of the important factors contributing to the critical impacts on nature, including eutrophication and biodiversity loss. To understand the effect of anthropogenic N emissions on urban-scale dry and wet N depositions, an investigation using a chemical transport model coupled with a sensitivity analysis solver was conducted in the domains that hold large megacities in Japan, the Tokyo metropolitan area, and Osaka, in the whole year of 2017. The validation results from the comparison of the modeling results to the observed results of N depositions showed that the overall calculated results replicated the observed results in the same order of magnitude. The results of the whole year calculation showed that both dry and wet N depositions were higher in spring and summer, mainly due to the higher emission of ammonia (NH3) due to the higher temperatures in those seasons. The results of the sensitivity analysis showed that NH3 was the most critical anthropogenic emission to the urban-scale N depositions, revealing the importance of the strategy to mitigate NH3 reduction. The findings of this study provide a basic understanding of urban-scale N deposition in terms of atmospheric chemistry and anthropogenic emission of N compounds.