Assessment of air quality before and during the COVID-19 and its potential health impacts in an arid oasis city: Urumqi, China.

As a key node city of the "Silk Road Economic Belt" Urumqi has been listed as one of the ten most polluted cities in the world, posing a serious threat to the urban environment and residents' health. This study analyzed the air quality before and during the COVID-19 (Coronavirus disease 2019) pandemic and its potential health effects based on the data of PM2.5, PM10, SO2, NO2, CO, and O3_8h levels from 10 air quality monitoring stations in Urumqi from January 1, 2017, to December 31, 2021. As per the results, the concentrations of the air pollutants PM2.5, PM10, SO2, NO2, CO, and O3_8h in Urumqi from 2017 to 2021 showed a cyclical trend, and the implementation of COVID-19 prevention and control measures could effectively reduce the concentration(ρ) of air pollutants. The mean value of ρ(PM2.5) decreased from 2017 to 2021, whereas ρ(O3_8h) showed a waveform change trend (increased in 2017-2018, decreased in 2018-2020, and increased after 2020). Meanwhile, the maximum annual average values of ρ(PM2.5) and ρ(O3_8h) for the six monitoring stations during 2017-2021 occurred at sites S2 (74.37 µg m-3) and S6 (91.80 µg m-3), respectively; rapid industrialization had a greater impact on PM2.5 and O3_8h concentrations compared to commercial and residential areas. In addition, the air quality index data series can characterize the fluctuation trend of PM2.5. The high pollution levels (Class IV and V) of the air pollutants PM2.5 and O3_8h in Urumqi have been decreasing annually, and good days can account for 80-95% of the total number of days in the year, indicating that the number of days with a potential threat to residents' health is gradually decreasing. Therefore, more attention should be paid in controlling and managing air pollution in Urumqi.

Temporal and spatial variation of NO2 in oasis cities in Xinjiang based on hyperspectral remote sensing technology

In order to promote the implementation of the "14th Five-Year Plan for the Prevention and Control of Air Pollution in Key Regions”, and to control NO2 pollution in Xinjiang more effectively. Based on hyperspectral remote sensing technology, combined with ground monitoring technology, this paper studies the temporal and spatial changes of NO2 pollutants in valley-type oasis cities in Xinjiang. The research results show that: (1) The overall characteristics of NO2 concentration are as follows: "Twelfth Five-Year” period > "Eleventh Five-Year” period > "Thirteenth Five-Year” period;the largest decrease (−11.45%) during the "Eleventh Five-Year" period in autumn;During the "Twelfth Five-Year Plan” period, the winter has the largest decrease (−9.74%). In the past 15 years, the center of NO2 pollution concentration in northern Xinjiang was near the Ganquanbao Industrial Park at the junction of the southeastern suburbs of Urumqi and the southwestern part of Changji Prefecture, and the concentration in the study area of southern Xinjiang was near Aksu City. The NO2 concentration in Xinjiang is influenced by both local sources and air mass transport. The potential source areas of northern Xinjiang are mainly distributed in the central part of Xinjiang, mainly through Wuchangshi and other areas. The potential source areas of the southern slope of the Tianshan Mountains are mainly distributed in the southern part of Xinjiang, mainly through the Korla and Aksu areas. During the COVID-19 epidemic, the control of man-made pollution sources has played a significant role in air pollution control. This study can provide data reference for the prevention and control of air pollution in Xinjiang. © 2022 Science Press. All rights reserved.