Observing Urban Aerosols Using Co-Located NO₂ Enhancement from TROPOMI

Abstract

This study uses observations of NO₂ and aerosol index (AI) from tropospheric monitoring instrument (TROPOMI) in China to study the feasibility of using NO₂ as a tracer to track the urban emission of air pollutants. Urban aerosol emissions are difficult to track due to its mixing with background. Nitrogen dioxide gas is an important urban emissions from human activities, and an effective indicator of emissions sources, because it is short-lived and chemically decayed rapidly away from its sources. In view of the fact that nitrogen dioxide and aerosol are mainly emitted simultaneously in cities, the spatial distribution map of nitrogen dioxide concentration can be used to monitor the urban aerosol emission trajectory caused by atmospheric transport. In this study, we selected two cities (Shijiazhuang, Baotou) in China, and used observation data from the high spatial resolution TROPOMI satellite to compare the spatial distribution of NO₂ concentration and AI. First, the enhancement of NO₂ concentration is used to identify urban plumes, and then these plumes are analyzed to indicate the optical characteristics of aerosols. The results show that the concentration of NO₂ as a tracer can be a good indicator of the spatial distribution of urban aerosol emissions.