西安市PM_(2.5)污染的时空分布

On the spatial and temporal distribution regularity of PM_(2.5) pollutants in Xi'an

为探索PM2.5的分布规律及其影响因素,对2013年西安市13个监测站点的全年ρ(PM2.5)数据进行了统计与整理。分析了ρ(PM2.5)的时空分布,采用聚类分析、小波变换研究了ρ(PM2.5)的区域分布特征与年际变化及突变特征,并对相关因素进行了探讨。结果表明,西安市ρ(PM2.5)在时间分布上具有冬高夏低的特点,而在空间分布上则以市人民体育场和草滩监测点所在区域为ρ(PM2.5)高值中心;ρ(PM2.5)在空间上可分为3大类,纺织城监测点单独为1类,经开区与草滩监测点为2类,另外10个监测点为3类,聚类效果的相关系数为0.7994,显示聚类效果较好;在ρ(PM2.5)年际变化中,除了6月和7月以外,其他月份ρ(PM2.5)均值为147.29μg/m3,日照时间短和静风是导致ρ(PM2.5)发生突变的主要气象因素。

This paper aims to present its description and analysis of the distributive features of the smog by taking the urban areas of Xi＇an city as a case study sample. At the same time,it also intends to put forward some theoretical proposals in hoping to improve the environmental protection work. As is known to everyone,the main trouble-maker of the smog pollution is PM2. 5,which tends to induce numerous kinds of diseases and may seriously harm human health. Innumerous as there may be on the studies of the pollution of PM2. 5in the country,most of them are attempting to shed light on its chemical constituent components,whereas it is rare to see quantitative and qualitative studies and analysis based on the real time data that have been collected and classified under close monitoring activities under way（ as the corresponding departments of the Chinese government have done since 2013 in monitoring and collecting the actual PM2. 5concentrations）. Seeing the above situation,this paper intends to provide some theoretically significant information and data in the environmental protection from the pollution of smog. In hoping to clarify the distribution features of ρ（ PM2. 5） in accordance with the time and space context,we have chosen 13 sites in Xi＇an city with our research focus on its impacting factors,based on the analysis of the real-time monitoring data during a whole year period of 2013（ 365 days）. Furthermore,we have also conducted the cluster analysis with a purpose to discuss the regional distribution features of ρ（ PM2. 5） and its influential factors. In doing so,we have adopted the wavelet transformation method to make a detailed exploration of the features of ρ（ PM2. 5） in the particular spatial and temporal terms,including the seasonal change and the unexpected climatic variation. What＇s more,we have also taken into account some relevant meteorological factors. The results of our investigation and analysis show that： ρ（ PM2. 5） in Xi＇an tends to be higher in winter and lower in summer. In addition,it tends to be more serious with the ρ（ PM2. 5） in the busiest social public gathering centers in the downtown areas,such as in the People＇s Square and Caotan monitoring site. In general, the ρ（ PM2. 5） pollution in Xi＇an can be divided into 3 categories in correspondence with the 13 monitoring sites： Category 1—the textile industry area（ Fangzhicheng）; Category 2—the area of Jingkai（ the Economically opening area） and Caotan area,and Category 3,which includes the rest 10 monitoring sites. As a result,the positive correlation index of the cluster analysis has been found equal to 0. 799 4,which indicates that the regional distribution of ρ（ PM2. 5） is closely related to the regional industrial activities but not highly closely related to the climatic or metrological factors. And,in terms of the yearly change,the average ρ（ PM2. 5） of all the other months is 147. 29 μg/m3 except for June and July,which implies that the cloudy weather and static wind may serve as the major meteorological factors that are likely to account for the sudden change of ρ（ PM2. 5）.