Memory Behaviors of Air Pollutions and Their Spatial Patterns in China

Particulate matter (PM2.5 and PM10) and ozone (O-3) are the two major air pollutants in China in recent years. The fluctuations of PM2.5, PM10 and O-3 strongly depend on the weather processes and anthropogenic emission. These processes may lead to the existence of shortand long-term memory behaviors in air pollutants. Hence, here we use the autoregressive parameter a of the first-order autoregressive process [AR (1)] to characterize the short-term memory effects of pollutants. We estimate the scaling exponent a using detrended fluctuation analysis (DFA) for the long-term memory effects of air pollutants (PM2.5, PM10, and O-3) in summer and winter for different cities in China. Our results show that PM2.5, PM10, and O-3 have strong short-term and long-term memory characteristics both in summer and winter. Furthermore, both the short- and long-term memory effects are stronger in winter than summer for most cities associated with stronger and longer persistent weather systems in winter. In general, the scaling exponent a of PM2.5 and PM10 are smaller for northern cities than those of southern cities inChina. The long-termmemory patterns of O-3 are stronger in northern cities and weaker in southern cities in relative to those of PM2.5 and PM10 in winter. Our results show that the short- and long-term memory behaviors of air pollutions are dominated by the weather systems with different time scales.