汾渭平原PM2.5时空分布与演变特征分析

Spatial-temporal Variation and Evolution Characteristics Analysis of PM2.5 in Fenwei Plain

基于汾渭平原55个环境监测点日监测数据,结合近邻传播聚类方法和空间马尔科夫链等方法,探析2015—2020年汾渭平原PM2.5时空分布与演变特征。结果表明:(1)2015—2020年汾渭平原不同城市PM2.5年均浓度呈波动式下降趋势,空气质量稳步好转,PM2.5浓度季节变化呈冬季高、春秋次之、夏季低的“U”型周期变化特征。(2)PM2.5空间分布呈现聚集特征,且山地和峡谷地区空气质量较好,平原地区空气质量逐年转好,喇叭口地形区域污染较为严重。(3)2015—2020年PM2.5高值聚集监测站逐渐减少,低值聚集监测站逐渐增多,汾渭平原整体空气质量逐步好转,但空间差异依旧存在。(4)汾渭平原PM2.5浓度整体上存在向低浓度收敛趋势,各城市PM2.5浓度受相邻区域浓度的影响,且低浓度类型地区对相邻地区具有正向促进和带动作用。

Based on the daily monitoring data of 55 environmental monitoring points in Fenwei Plain from 2015 to 2020,the dynamic evolution of air pollution in Fenwei Plain was discussed by combining neighbor propagation clustering and space Markov chain methods.The results showed that:(1)The concentration of PM2.5 in Fenwei Plain fluctuated with a downward trend,indicating that the air quality improved steadily.It presented a“U”-shaped periodic characteristic that the PM2.5 concentration was worst in winter,followed by spring and autumn,and was the best in summer;(2)The spatial distribution of PM2.5 shows aggregation characteristics,and the air quality in mountainous and canyon areas is better,the air quality in plain areas is better year by year,and the pollution in trumpet mouth terrain area is more serious;(3)On the whole,the high value aggregation monitoring stations gradually decrease,the low value aggregation monitoring stations gradually increase,and the overall air quality of Fenwei Plain gradually improves,but the spatial difference still exists;(4)The dynamic evolution law shows that the overall PM2.5 concentration in the Fenwei Plain has a low concentration convergence trend.The PM2.5 concentration type of each urban area is affected by the concentration type of the adjacent area,and the low concentration type area has a positive promotion to the adjacent area and lead action.