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Mass-Conserving Inversion of NOx Emissions and Inferred Combustion Technologies in Energy Rich Northern China Based on Multi-Year Daily Remotely Sensed and Continuous Surface Measurements
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  • Xiaolu Li,
  • Jason Blake Cohen,
  • Kai Qin,
  • Hong Geng,
  • Liling Wu,
  • Xiaohui Wu,
  • Chengli Yang,
  • Rui Zhang,
  • Liqin Zhang
Xiaolu Li
Institute of Environmental Science
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Jason Blake Cohen
School of Environment Science and Spatial Informatics, China University of Mining and Technology

Corresponding Author:[email protected]

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Kai Qin
China University of Mining and Technology
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Hong Geng
Shanxi University
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Liling Wu
School of Environment, Tsinghua University
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Xiaohui Wu
Shanxi Dadi Ecology and Environment Technology Research Institute
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Chengli Yang
Shanxi Dadi Ecology and Environment Technology Research Institute
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Rui Zhang
Consulting Service Center of Ecologic and Environmental Protection of Shanxi Province (Shanxi Academy for Environment Planning)
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Liqin Zhang
Monitoring and Emergency Response Center of Ecology and Environment of Shanxi Province (Shanxi Institute of Ecologic and Environmental Science)
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Nitrogen oxides (NOx) are markers of combustion contributing to ozone, secondary aerosol, and acid rain, and are required to run models focusing on atmospheric environmental protection. This work presents a new model free inversion estimation framework using daily TROPOMI NO2 columns and observed fluxes from the continuous emissions monitoring systems (CEMS) to quantify emissions of NOx at 0.05°×0.05°. The average emission is 0.72±0.11Tg/yr from 2019 through 2021 over Shanxi, a major energy producing and consuming province in Northern China. The resulting emissions demonstrates significant spatial and temporal differences with bottom-up emissions databases, with 54% of the emissions concentrated in 25% of the total area. Two major forcing factors are horizontal advective transport (352.0±51.2km) and first order chemical loss (13.1±1.1hours), consistent with a non-insignificant amount of NOxadvected into the free troposphere. The third forcing factor, the computed ratio of NOx/NO2, on a pixel-by-pixel basis has a significant correlation with the combustion temperature and energy efficiency of large energy consuming sources. Specifically, thermal power plants, cement, and iron and steel companies have high NOx/NO2 ratios, while coking, industrial boilers, and aluminum show low ratios. Variance maximization applied to the daily TROPOMI NO2 columns identifies three modes dominate the variance and attributes them to this work’s computed emissions, remotely sensedTROPOMI UVAI, and transport based on TROPOMI CO. Using satellite observations for emission estimates in connection with CEMS allows the rapid update of emissions, while also providing scientific support for the identification and attribution of anthropogenic sources.