中文摘要：

PM2.5是造成雾霾天气、降低能见度,影响交通安全的主要因素。首先基于主成分分析法分析得出PM10最能影响PM2.5浓度变化,再利用联合多重分形探究不同城市的PM2.5与PM10之间的关系。从而得出西安市及伦敦市的PM2.5和PM10之间的关系具有一致性,即PM10浓度偏低时PM2.5也偏低,而PM10浓度偏高时PM2.5却偏低。无论PM10浓度如何变化,相对而言,伦敦市PM2.5浓度波动更剧烈些。

英文摘要：

PM2. 5 is the main factor to cause haze weather, low visibility and affect traffic safety. Firstly, use principal analysis to know that the change of PM10 concentration can influence the change of PM2. 5 concentration. Then the relationship between PM2. 5 and PM10 in different cities are to be known by joint multifractal. So it has been found that the relationship between PM2.5 and PM10 in different cities are consistent. Specifically, PM2. 5 concentration is always in low level when PM10 concentration has different levels. No matter how changes the concentration of PM10, relatively speaking, the PM2.5 concentration fluctuation of London is even stronger than Xi＇an.