Spatiotemporal patterns of air quality and its dominant factors in middle–lower reaches of Yellow RiverOA

Monitoring air quality is a core scientific issue in atmospheric environmental research.Based on the hourly air quality index(AQI)data from 298 monitoring stations,a multi-scale analysis of air quality was conducted in the middle–lower reaches of the Yellow River from June 2016 to May 2020.Methodologically,unified quality control and missing-data imputation were applied to the hourly AQI records,after which annual,seasonal,and monthly mean AQI values were calculated using arithmetic averaging.The Kriging interpolation was applied to map multi-temporal spatial patterns,while the coefficient of variation and global/local spatial autocorrelation were used to quantify spatial disparity and clustering of AQI.Then,the effects of natural and socioeconomic factors were identified and cross-validated using the geographical detector and multiple linear regression.The results show that AQI exhibits a pronounced downward trend over time,with clear seasonal characteristics and cyclical variations at the monthly scale;spatially,AQI has long displayed a pattern of higher values in downstream and lower values in midstream,with high-concentration areas mainly clustered in the adjacent regions of Henan,Shandong and Shanxi provinces;significant positive spatial autocorrelation is observed at all temporal scales,with stable high–high and low–low clustering patterns;population density,civilian vehicle ownership,and industrial dust emissions show the strongest explanatory power,while air temperature and afforestation area exert moderating effects on AQI variations.This study is of potential significance to cross-provincial coordinated control and refined air pollution management.