新冠疫情期间西安市空气质量时空特征研究

Spatial-temporal characteristics of air quality in Xi'an during the COVID-19 pandemic

2019年和2021年新冠疫情期间西安市政府均采取了强有力的管控措施,为此对比研究了不同程度减排措施对空气质量的影响。采用特征雷达图、空间插值和HYPLIST轨迹模型等方法对西安市疫情期间(2019年12月—2020年2月、2021年12月—2022年2月)和正常生产期(2020年12月—2021年2月)冬季空气质量变化特征进行了对比分析,并探讨了人为减排情景下空气质量变化潜在原因。结果表明:(1)西安市环境空气质量指数(AQI)空间分布整体呈现“西北劣东南优”特征。2020年疫情严控期空气质量得到明显改善,优良率达到53%;2022年疫情严控期空气质量未受管控措施明显影响。(2)2020年疫情严控期除O_(3)外污染物浓度均明显下降,降幅分别为PM2.5(42.90%)>NO_(2)(42.13%)>CO(35.37%)>PM10(32.58%)>SO_(2)(17.40%);2022年仅有SO_(2)和NO_(2)浓度下降,降幅为NO_(2)(31.86%)>SO_(2)(18.31%)。疫情期间污染类型属于偏二次型。(3)疫情期间,污染天气是在高湿静风天气条件和盆地地形的基础上,受人为源排放和区域污染物传输引起的,因此促进污染物协同减排和关中地区联防联控是改善空气质量的关键举措。

During the COVID-19 pandemic in 2019 and 2021,strong control measures were taken in Xi'an,China,therefore,the impact of different degrees of emission reduction measures on air quality was studied comparatively.In this work,the characteristics of air quality changes during the pandemic period(December 2019-February 2020 and December 2021-February 2022)and the normal production period(December 2020-February 2021)in Xi'an were compared and analyzed by methods of characteristic radar map,spatial interpolation and HYPLIST trajectory model,and the potential causes of air quality change under anthropogenic emission reduction scenarios were discussed.The results show that:(1)The overall spatial distribution of air quality index(AQI)in Xi'an exhibits a characteristic of"inferior in northwest and superior in southeast".In 2020,the air quality of Xi'an city was significantly improved during the strict pandemic control period,with 53%days with the air quality being excellent and good.While in 2022,the air quality was not significantly affected by the strict epidemic control measures.(2)During the strict control period of the epidemic in 2020,except for O_(3) the concentrations of other pollutants,decreased significantly,with PM2.5(42.90%)>NO_(2)(42.13%)>CO(35.37%)>PM10(32.58%)>SO_(2)(17.40%).While in 2022,only SO_(2) and NO_(2) concentrations decreased,with a decrease of NO_(2)(31.86%)>SO_(2)(18.31%).The type of pollution during the pandemic was mainly secondary pollution.(3)During the pandemic period,polluted weather was mainly caused by anthropogenic source emissions and regional pollutant transport on the basis of high humidity,calm wind weather conditions and basin topography.Therefore,promoting the coordinated reduction of pollutant emission,as well as joint prevention and control in Guanzhong area,is the key measure to improve air quality.