Satellite Remote Sensing Of The Nitrogen Dioxide Emissions From Typical Anthropogenic Sources In China

Nitrogen oxide(NOx) emissions make great contributions to the complex air pollution in China. The typical NOx sources include power plants, industrial activities and vehicles. In terms of spatial distribution, typical NOx sources are either large point sources like power plants or located in urban areas. Emission estimates for cities and power plants based on traditional method including bottom-up inventory exhibit large uncertainties. The rapid development of satellite observations provides a new technique for NOx emission quantification recently. The measurements of NO2 columns from satellites detect emission plumes from cities and power plants, showing elevated NO2 values near emission sources like large point sources. Based on the characteristic of emission plumes, this study aims to quantify emissions and their historical trends from cities and power plants in China by taking advatanges of satellite observations,providing a new technique for the quantification of emissions and their evaluation of the accuracy of emissions inventories, and then analyze driving forces of emission trends.Firstly, based on the collected information consisting of about 8000coal-fired electric generating units in China, a unit-based database at high spatial and temporal resolution was constructed by the assimilation and integration of multi-source data to estimate NOx emissions at unit level for the period of 1990–2012. Compared to extant inventories, the magnitude and spatial distribution of the emissions in the power plant inventory developed by this study present higher resolution. And then urban emission inventories based on Multi-resolution Emission Inventory for China(MEIC) were establised by calculating emissions as provincial totals and distributing them to grids using spatial proxies. Due to the limitation of the accuracy of spatial proxies,MEIC-based urban emission trends are dominated by changes of total emissions of corrsponding provinces and thus have large uncertainties.Second, based on the developed emission inventories above, the emission plumns from cities and power plants in OMI NO2 tropospheric vetical columnswere detected. Based on the detected plumns, new one-dimentional emission inverse model of quantifications of NOx emissions and two- dimentional model of quantifications of emission changes for non-isolated emission sources were developed, using OMI NO2 columns coupled with meteorological reanalysis data. NOx emissions and their historical trends from cities and power plants in China were quantified by the two inverse models to assess the accuracy of emissions inventories. Power plant emissions estimated by inventory are in good agreement with the inversed NOx emissions and their temperal changes from satellite data,indicating the high accuracy of the power plant inventory developed by this study. While, the consistancy between emission inventories and inversed emissions for cities is not as good as that for power plants, indicating that MEIC-based urban emission trends have large uncertainties.Based on an overall consideration of the inversed NOx emissions, emission inventories and social economic parameters, driving forces of emission changes were analyzed. Emissions emited by power plants and cities peaked at 2012 and declined thereafter. The primary contributors of the decline in urban and power plant emissions are the more strigent emission standards for vehicles and industrial upgrade and structural adjustment for cities, and the installation of de-NOx devices for power plants, respectively.