Methodology:
Time series analysis is an
appropriate method to analyze air pollution, since the index of air quality is continuous
as time. Rolling means and rolling deviations are made to help realize the trend
of PM2.5 Value in Beijing. Event detection is also used with the sudden declining
trend of time series plot of PM2.5 Value. After searching about it, it is
confirmed to be the military parade in September in Beijing, when hundreds of
factories were shut down and 2.5 million cars were banned. We can conclude that
factory emissions and vehicle emissions are main factors of air pollution in
Beijing. With the comparison of north and south cities, we can also conclude that
coal burning is another main factor.