In this paper, satellite data from five isolated power plants were used to explore the change local emissions levels belonged to the vicinity of the power plant before and after ultra-low emissions (ULE) retrofitted. Sulphur dioxide (SO2) and nitrogen dioxide (NO2) observations from Ozone monitoring Instrument (OMI) satellite data were used to evaluate the emission changes of the power plants retrofitted by ULE technology. Meanwhile, the actual emission reduction effect of isolated power plants was evaluated by the OMI data. It was observed that the isolated power plants have shown obvious point source characteristics. The average annual SO2 emission reduction ratio of SZ, ZD, JJ, ND and BD power plants after ultra-low transformation is 43.7%, 56.9%, 29.0%, 34.6% and 26.8%, respectively, compared with that before the transformation, while the corresponding PBL-SO2 column concentration reduction ratio is 27.0%, 14.3%, 15.6%, 26.6% and 4.2%, respectively. The average annual NOx emission reduction ratio of the power plants after ultra-low transformation is 44.7%,79.3%,29.0%,73.2% and 29.8%, respectively, compared with that before the transformation, while the corresponding NO2 column concentration reduction ratio is 7.0%,27.2%,25.7%,8.9% and 5.6%, respectively. The trend of emission reduction before and after the ULE retrofitted of SO2 and NO2 column concentration by satellite observation is consistent with the calculated trend of emission reduction. Satellite observations have confirmed the emission reduction effect of ULE technology.
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