Abstract
Abstract. The rapid growth of economy makes China the largest energy consumer and sulfur dioxide (SO2) emitter in the world. In this study, we estimated the trends and step changes in the planetary boundary layer (PBL) vertical column density (VCD) of SO2 from 2005 to 2015 over China measured by the Ozone Monitoring Instrument (OMI). We show that these trends and step change years coincide with the effective date and period of the national strategy for energy development and relocation in northwestern China and the regulations in the reduction of SO2 emissions. Under the national regulations for the reduction of SO2 emissions in eastern and southern China, SO2 VCD in the Pearl River Delta (PRD) of southern China exhibited the largest decline during 2005–2015 at a rate of −7 % yr−1, followed by the North China Plain (NCP) (−6.7 % yr−1), Sichuan Basin (−6.3 % yr−1), and Yangtze River Delta (YRD) (−6 % yr−1). The Mann–Kendall (MK) test reveals the step change points of declining SO2 VCD in 2009 for the PRD and 2012–2013 for eastern China responding to the implementation of SO2 control regulation in these regions. In contrast, the MK test and regression analysis also revealed increasing trends of SO2 VCD in northwestern China, particularly for several hot spots featured by growing SO2 VCD in those large-scale energy industry bases in northwestern China. The enhanced SO2 VCD is potentially attributable to increasing SO2 emissions due to the development of large-scale energy industry bases in energy-abundant northwestern China under the national strategy for the energy safety of China in the 21st century. We show that these large-scale energy industry bases could overwhelm the trends and changes in provincial total SO2 emissions in northwestern China and contribute increasingly to the national total SO2 emissions in China. Given that northwestern China is more ecologically fragile and uniquely susceptible to atmospheric pollution than the rest of China, increasing SO2 emissions in this part of China should not be overlooked and merit scientific research.
Highlights
Sulfur dioxide (SO2) is one of the criteria air pollutants emitted from both anthropogenic and natural sources
The highest SO2 vertical column density (VCD) was found in the North China Plain (NCP), including BTH, Shandong, and Henan
The clearly visible “hot spots” featured by increasing OMImeasured SO2 VCD in the Energy Golden Triangle (EGT)/Ningdong Energy Chemical Industrial Base (NECIB) and Midong Energy Industrial Base (MEIB) raise a question: to what extent could these large-scale energy industrial bases affect the trend and fluctuations of SO2 emissions in northwestern China? Figure 7 illustrates the fractions (%) of Ozone Monitoring Instrument (OMI)-measured annual SO2 VCD and SO2 emissions averaged over the six provinces of northwestern China in the annual national total VCD (Fig. 7a) and emissions (Fig. 7b) from 2005 to 2015
Summary
Sulfur dioxide (SO2) is one of the criteria air pollutants emitted from both anthropogenic and natural sources. That, in contrast to dramatic decreasing SO2 emissions in densely populated and industrialized eastern and southern China, the OMI-measured SO2 in northwestern China appeared not to show a decreasing trend. This likely resulted from energy industry relocation and development in energyabundant northwestern China in the past decades under the national strategy for China’s energy development and safety during the 21st century. Ling et al.: OMI-measured increasing SO2 emissions to (1) determine the spatiotemporal variations of SO2 and its trend under the national plan for energy industry development in northwestern China by making use of the OMImeasured SO2 data during 2005–2015 and (2) identify leading causes contributing to the enhanced SO2 emissions in northwestern China
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