Abstract:

Nitrogen dioxide (NO₂) is one of the main atmospheric pollutants and the concentration of NO₂ is mainly determined by human activities. The occurrence of the novel coronavirus epidemic in the early 2020 has restricted work and normal life, which in turn greatly affected NO₂ emissions. Shaanxi Province is the frontier of the Silk Road to the west and a golden place in the One Belt and Road region. Investigating the temporal and spatial variation characteristics of NO₂ during the COVID-19 epidemic period and the changes of social-economic activities during this time is of great significance for scientific understanding of the relationship between human activities and pollutants in Shaanxi Province. Taking Shaanxi Province as the study area, we selected four important periods from January 21, 2020 to January 22, 2022: year-on-year period, sequential period, epidemic period I and epidemic period II. Based on the most advanced TropOMI data with the highest spatial resolution, we used standardized socio-economic life index (SSEI) and NO₂ emission reduction effect estimation methods to study the spatio-temporal distribution characteristics and the impact of COVID-19 on NO₂ and socio-economic life in Shaanxi Province. The results showed that (1) there was a positive correlation between NO₂ concentration from surface monitoring and NO₂ column concentration from TropOMI inversion, and the results of tropospheric NO₂ column concentration from TropOMI inversion were reliable. (2) The tropospheric NO₂ column concentrations in Shaanxi Province during the epidemic period I decreased by 39.15% and 55.99% respectively, compared with those during the year-on-year and the chain periods, and decreased by 59.29% compared with that in the epidemic period II. In Shaanxi province, the areas with high tropospheric NO₂ column concentrations were significantly affected by COVID-19 pandemic, while areas with low NO₂ column concentrations were less affected. Spatially, tropospheric NO₂ column concentrations were higher in Guanzhong, northern Shaanxi and around cities than in other areas. (3) Socio-economic activities in Shaanxi Province were greatly affected by the epidemic control. In 2020, 2021 and 2022, the overall changing trends of SSEI for a total of 13 weeks, including 5 weeks before and 7 weeks after the Chinese New Year, remained the same. The SSEI in Shaanxi Province during the epidemic period I in 2020 were significantly lower than those in the epidemic-free period in 2021 and the epidemic period II in 2022. In conclusion, the variation of NO₂ is closely related to human activities, and the NO₂ concentration data obtained from remote sensing inversion can be used to evaluate socio-economic life in on a large scale from different dimensions.

Key words: Nitrogen dioxide, temporal and spatial distribution, COVID-19, socio-economic life, TropOMI, Shaanxi Province

摘要：

二氧化氮（NO₂）是重要的大气污染物之一，其浓度水平主要受人类活动影响。2020年初新冠疫情发生，人民生产生活受到限制，进而对NO₂的排放产生了重要影响。陕西省作为丝绸之路向西推进的前沿、“一带一路”战略中的黄金要地，开展新冠疫情背景下NO₂时空变化特征及其所反映的社会经济活动变化，对于科学认识陕西省人类活动与污染物之间的相互关系具有重要意义。以陕西省为例，在2020年1月21日-2022年1月22日期间选取同比期、环比期、疫情期I、疫情期II共4个重要时段，基于目前技术性能最先进、空间分辨率最高的TropOMI数据，利用标准化社会经济活动指数（SSEI）、NO₂减排效应估算等方法，开展了陕西省新冠疫情对NO₂时空分布特征和社会经济活动影响研究。结果表明，（1）地面监测NO₂浓度与TropOMI反演的NO₂柱浓度呈现较好的正相关关系，利用TropOMI反演的对流层NO₂柱浓度数据具有较高可靠性。（2）疫情期I陕西省对流层NO₂柱浓度较同比期和环比期分别下降39.15%和55.99%，较疫情期II下降59.29%。新冠疫情导致陕西省对流层NO₂柱浓度高的地区下降明显，而低的地区受影响相对较小。对流层NO₂柱浓度在空间上总体表现为关中地区和陕北北部及城市周边高于其他地区的分布特征。（3）陕西省社会经济活动受疫情管控影响较大。2020、2021、2022年春节前5周至春节后7周共13周的SSEI总体变化趋势保持一致。2020年疫情期I陕西省SSEI明显低于2021年同时段无疫情时期和2022年疫情期II。研究结论认为NO₂变化与人类活动关系密切，利用TropOMI遥感反演的NO₂浓度数据可用于开展大范围、多尺度的社会经济活动评价。

关键词: 二氧化氮, 时空分布, 新冠疫情, 社会经济活动, TropOMI, 陕西省