Considerable Unaccounted Local Sources of NOx Emissions in China Revealed from Satellite

Environ Sci Technol. 2022 Jun 7;56(11):7131-7142. doi: 10.1021/acs.est.1c07723. Epub 2022 Mar 18.

Abstract

High-resolution (e.g., 5 km) emission data of nitrogen oxides (NOx = NO + NO2) 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 NOx emissions in China at a 5-km resolution in summer 2019, based on the TROPOMI-POMINO satellite product of nitrogen dioxide (NO2) columns. With low computational costs, our inversion explicitly accounts for the effects of horizontal transport and nonlinear chemistry. We find numerous small-to-medium sources related to minor roads and small human settlements at relatively low affluence levels, in addition to clear emission signals along major transportation lines, consistent with road line density and Tencent location data. Many small-to-medium sources and transportation emissions are unclear or missing in the spatial distributions of four widely used emission inventories. Our emissions offer a unique reference for targeted emission control.

Keywords: China; NOx emission; TROPOMI; high resolution; satellite.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Air Pollutants* / analysis
  • Air Pollution* / analysis
  • China
  • Environmental Monitoring
  • Humans
  • Nitrogen Dioxide / analysis
  • Nitrogen Oxides / analysis
  • Vehicle Emissions / analysis

Substances

  • Air Pollutants
  • Nitrogen Oxides
  • Vehicle Emissions
  • Nitrogen Dioxide