Scaling properties of air pollution in Athens, Greece and Baltimore, Maryland

Detrended fluctuation analysis is applied to the Athens air-pollution time-series consisting of hourly observations of ozone, nitrogen oxides, and particulate matter obtained at five air-pollution monitoring stations during 1987–2003. Persistent power-law correlations in the fluctuations of daytime and nighttime ozone concentrations with lag times ranging from 1 week to 5 years were detected with more intense correlations (“stronger memory”) during daytime. The fluctuations of nitrogen oxide concentrations exhibit similar behavior. Finally, persistent power-law correlations from about 4 h to 9 months were found in PM10 fluctuations in Athens. Long-range correlations for lag times from about 4 h to 2 weeks were also detected for PM2.5 fluctuations in a 6-month data set collected at the University of Maryland “Supersite” in East Baltimore. Although the origin of the long-range behaviour of air-pollution merits further investigation, these findings presumably, reflect short and longer term source/meteorological features that are probably related to the self-organized critical behavior of the atmosphere. These findings provide power-law relationships which may substantially contribute to the development of more reliable simulating models for the ozone, nitrogen oxides, and particulate matter fluctuations.