OMI-measured SO2 in a large-scale national energy industrial base and its effect on the capital city of Xinjiang, Northwest China

Abstract

Although considerable efforts have been made to improve air quality in Urumqi city, the capital of Xinjiang-Uyghur Autonomous Region in northwestern China and one of the ten cities with worst air quality in China, this city is still experiencing heavy air pollution during the wintertime. The satellite remote sensing of air quality using Ozone Monitoring Instrument (OMI) measured data discerned an increasing trend of the planetary boundary layer (PBL) columns of sulfur dioxide (SO2) in Midong national petrochemical and coal chemical industry base from 2005 to 2016, located in the northeast of Urumqi. The increasing trend of OMI columnar SO2 in this area is in contrast to the widespread decreases in SO2 emissions in eastern and southern China. This is mainly induced by rapid development in the energy industry in this region over the past decade under the national strategy for energy industry expansion and relocation to northwestern China. We observed a significant correlation of OMI columnar SO2 between this energy industrial base and Urumqi city in winter (R = 0.504, p < 0.005), suggesting that SO2 emitted from heavily contaminated energy industrial base exacerbated the air quality in Urumqi city. The Weather Research and Forecasting Chemistry (WRF-Chem) modeling confirms that the occurrence of heavy smog in this capital city during the wintertime was attributed primarily to strong emissions of air contaminants from the energy industrial base under favorable winds. A numerical case study with and without taking the Midong Industry Base into consideration revealed that this industry base contributed 38% to the SO2 level in Urumqi city, offsetting the considerable efforts made by the local government to improve air quality in this city.