Research On PM_2.5 Pollution Mode Based On Frequent Patterns Among Cities Of China

In recent years, air pollution problems are becoming increasingly prominent, seriously affecting people’s lives and living environment. Especially in China, the harm is becoming more serious. Beijing, Shanghai, Hangzhou, Shenyang and other cities face up to high pollution frequently, therefore, air pollution control has become the top priority of our governance policies. As one of the most important components of haze, PM2.5 pollution can’t be ignored. Existing research on PM2.5 mostly uses small samples and concentrates in spatiotemporal distribution, source apportionment, impact on atmospheric visibility and human health and other aspects. Most research on spatial and temporal distribution is mainly based on statistical methods, and analyzes separately from the two dimensions of time and space, but there is no integration of the two dimensions. Research on PM2.5 influencing factors mainly through component analysis so as to infer the factors. Some scholars have also analyzed from a macro point of view, but mainly considered economic factors, and the scope is not comprehensive enough. In this paper, we based on data-driven, first studied the overall spatial and temporal distribution of urban PM2.5 in 2015, and focused on three economic zones, they are Bohai Sea, Yangtze River Delta and Pearl River Delta. Then a sequential pattern mining method was used to mine temporal and spatial pollution correlation among cities in each economic zone. Finally, combined with data of city PM2.5 in 2014, as well as City Statistical Yearbook 2015, we proceed from a plurality of different angles to explore potential influencing factors on the macro.The basic results are as follows:(1) The 24-hour and monthly average variation of PM2.5 in three economic zones in 2015 have similar regularity. The 24-hour curve has two peaks and two valleys, and monthly curve shows higher pollution in winter, while in summer the pollution level is the lowest. Only a few cities in the country have achieved the primary standard, most cities are much higher than this limit.(2) Hebei and Shandong are provinces which are frequently polluted in Bohai Sea region. The pollution center gradually moved south, and the entire economic zone faces high degree of contamination all over the year. The pollution sequential patterns in Yangtze River Delta in the four seasons have regularity, and patterns show opposite directions between spring and winter. In addition, when the coastal urban occurs pollution, the next day inland cities are more prone to appear contamination. Patterns in Pearl River Delta point from densely populated cities to non-densely populated cities, forming a complex network of pollution, and contamination occurs mainly in the central and western regions.(3) Northern and Eastern China suffers higher annual average of PM2.5, which generally also have higher area of land used for urban construction and living, total gas supply and so on. cities in North China have lower seasonal ratio, some indicators show positive association relationship with seasonal ratio, for example, when the annual electricity consumption is low, seasonal ratio of PM2.5 is also low, and there are indicators showing negative association, such as volume of sulphur dioxide emission, GDP, etc. When start from the perspective of weekday-weekend ratio, we found that southern China have higher weekday-weekend ratio. When number of industrial enterprises, population with access to liquefied petroleum gas and other seven indicators keep a low level, the ratio is higher.Air pollution control is a huge project. There is still a long way to go for China, which requires the joint efforts of individuals, collectives and even the whole country.