Abstract
Scaling and multifractal properties of the hourly PM2.5 average concentration series at the four air monitoring stations of Chengdu (southwestern China) were explored by using a multifractal detrended fluctuation analysis method, during a typical haze episode (from 1 March to 17 March, 2013). Using shuffling procedure and phase randomization procedure, the major sources of multifractality in these PM2.5 series are studied. The results show that the multifractality nature of PM2.5 series is mainly due to long-range correlation. At the same time, the non-Gaussian probability distributions also partly contribute to the multifractal behaviour. The scale-free power laws behaviours are found to govern the cumulative distributions statistics for PM2.5 concentration fluctuations. The temporal evolutions of the multifractality were investigated by the approach of a sliding window. Further, we attempt to find the answers to the following questions: how does longrange correlation and power-law distribution in PM2.5 evolution emerge? It is inviting to do it in a self-organized criticality (SOC) framework, which was specially designed to model the dynamics of complex systems. A novel PM2.5 evolution model is developed on the bases of SOC theory. The model displays robust power law behaviour in certain dynamical region. The self-organized criticality properties of PM2.5 evolution are discussed. This SOC behaviour is related to a statistically steady state that implies the presence of long-range correlation and power-law distribution in PM2.5 evolution during the haze period. It is the stability of SOC that causes the haze period to be sustained for a long time in Chengdu.
Highlights
Chengdu (30.67°N, 104.06°E) is the largest city in southwestern China, with a population of about 11 million and an area of about 12,000 km2
There are no significant differences among these time dependence of ∆h during the whole haze period. It implied that the underlying mechanism of PM2.5 fluctuations in the formation of multifractality is consistent during the haze period
During a typical haze period, the scaling and multifractal properties of PM2.5 concentrations series of the four monitoring stations in Chengdu have been analyzed by MF-detrended fluctuation analysis (DFA)
Summary
Chengdu (30.67°N, 104.06°E) is the largest city in southwestern China, with a population of about 11 million and an area of about 12,000 km. Chengdu (30.67°N, 104.06°E) is the largest city in southwestern China, with a population of about 11 million and an area of about 12,000 km2 It is located in the western portion of the Sichuan Basin. Chengdu city is surrounded by Longquan Mountain to the east and Qionglai Mountain to the west of the city. The unique topographical condition directly affects meteorological condition of pollutant diffusion. The prevailing wind direction in Chengdu is from the north. With rapid economic growth and increasing energy consumption, particulate matter (PM) pollution has become the primary environmental problem in Chengdu. It is considered to be one of the four regions in China most
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