京津冀及周边城市PM2.5污染空间关联网络及季节演化研究

Spatial Correlation Network and Season Evolution of PM2.5 Pollution in Beijing-Tianjin-Hebei and Surrounding Cities

京津冀及周边城市是雾霾频发的重灾区,研究该地区城市的PM2.5污染空间关联网络及其随季节演化情况,对于雾霾污染的协同治理具有重要的意义。选取2015年3月16日—2020年3月15日期间,京津冀及周边31个城市的日均PM2.5浓度数据作为样本。首先,对不同城市PM2.5浓度值的时序变化与空间分布进行了可视化展示;然后以城市为节点,城市日均PM2.5浓度值皮尔逊相关系数为边,相关系数与城市最短距离的比值为权重构建京津冀及周边城市PM2.5污染空间关联网络,并对网络的整体特征与季节演化情况进行了分析。结果表明,京津冀及周边城市PM2.5污染空间关联网络图密度为0.473,平均度为14.194,网络图比较紧密;在区域内部,聚类系数较高城市大多位于中间城市带,PM2.5污染也较为严重;石家庄与邢台的度值最高,分别为26与25,接近中心性与中介中心性也最高,控制其他城市PM2.5污染传输的能力最强;在不同季节,城市PM2.5指数相关性对比存在较大差异,采暖季平均聚类系数为0.82,非采暖季平均聚类系数为0.66,在采暖季城市PM2.5污染空间关联更为紧密。因此,应当根据不同季节的气象条件,制定不同的PM2.5污染防治政策,对于污染均比较严重的,位于中间城市带的城市,应重点监控,并积极推进京津冀及周边城市PM2.5污染的一体化与协同治理。

Beijing-Tianjin-Hebei and surrounding cities are the worst-hit areas of frequent haze.It is of great significance to investigate the spatial association network of haze pollution among these cities and its evolutionary process with the seasons.This paper selects the daily average PM2.5 concentration data in 31 cities from March 16th,2015,to March 15th,2020 as the sample data.Firstly,temporal variation and spatial distribution of PM2.5 concentration values in different cities were visualized.Secondly,the Beijing-Tianjin-Hebei and surrounding city haze pollution spatial association network is established.The node is the city,the edge is the Pearson correlation coefficient of urban daily average PM2.5 concentration and the weight is related to the correlation coefficient and the ratio of the shortest distance of the city.Thirdly,the overall characteristics of the network and seasonal evolution are analyzed.Our findings indicate that the density of PM2.5 pollution spatial correlation network is 0.473,the average degree is 14.194 and the network is relatively tight.From the region perspective,cities with high clustering coefficient are mostly located in the middle urban belt,and PM2.5 pollution is also serious.Shijiazhuang and Xingtai has the highest degree,26 and 25 respectively.They also have the highest closeness centrality and between centrality,and have the strongest ability to control PM2.5 pollution transmission in other cities.From the season perspective,the correlations of urban PM2.5 index in these cities are different.The average clustering coefficient is 0.82 in heating season and 0.66 in non-heating season,and the spatial correlation of PM2.5 pollution is more closely in heating season.Therefore,different policies for the prevention and control of haze pollution should be formulated according to the meteorological conditions of different seasons.The cities located in the middle city belt should be monitored,where the pollution is more serious.In addition,the integration of haze pollution in Beijing-Tianjin-Hebei and surrounding cities,and coordinated treatment should be actively promoted.