Considerable unaccounted local sources of NOx emissions in China revealed from satellite

High-resolution (e.g., 5 km) emission data of nitrogen oxides (NO x =N O+N O 2) provide localized knowledge of pollution sources for targeted regulations, yet such data are lacking or inaccurate over most regions at present. Here we improve our PHLET-based inversion method to derive NO x emissions in China at a 5-km resolution in summer 2019, based on the TROPOMI-POMINO satellite product of nitrogen dioxide (NO 2) columns. With low computational costs, our inversion explicitly accounts for the e ffects of horizontal transport and nonlinear chemistry. We find numerous small-to-medium sources related to minor roads and small human settlements at relatively low a ffluence levels, in addition to clear emission signals along major transportation lines, consistent with road line density and Tencent location data. Many smallto-medium sources and transportation emissions are unclear or missing in the spatial distributions of four widely used emission inventories. Our emissions o ffer a unique reference for targeted emission control.