title: Multifractal nature of particulate matters (PMs) in Hong Kong urban air.
abstract: In this study, we investigate the persistent variation and the multifractal nature of particulate matter (PM) concentrations from vehicle emissions at a typical traffic intersection of street canyon in Hong Kong. Six size groups of PMs are measured and collected during rush hour sessions on different dates respectively. A recently developed model, namely multifractal detrended fluctuation analysis (MF-DFA), is employed to decompose and analyze the collected database. Through estimating the scaling exponent, it is found that the PM levels from vehicular emissions display long-term correlation characters. By employing MF-DFA method to calculate the generalized Hurst exponent and discuss the multifractal spectrums of all size groups, it is noticed that the fine particulate matters in grain diameter of 0.3-0.499 μm present strong multifractal nature, intensive oscillations of concentration variations, and long-term persistence. For fine particulate matters in the grain diameter ranges from 0.5 μm to 4.99 μm, their similar and weak multifractal natures reflect the self-similarity behaviors among these groups and the gradual decreases of the lasting effects. For large size particulate matters, i.e., grain diameter above 5 μm, certain mono-fractal nature and sharp decay of long-term persistence are obtained, even for intermittent effects. It can therefore be concluded that the fine particulate matter diffuses anomaly and persists for a long time.
authors.affiliation: Institute of Physical Sccbvience and Engineering, Guangxi University, Nanning 53004, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Xue
authors.affiliation: Institute of Physical Sccbvience and Engineering, Guangxi University, Nanning 53004, China; Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong.
authors.forename: Wei
authors.initials: W
authors.lastname: Pan
authors.affiliation: Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong. Electronic address: bcwzlu@cityu.edu.hk.
authors.forename: Wei-Zhen
authors.initials: WZ
authors.lastname: Lu
authors.affiliation: Logistics Research Center, Shanghai Maritime University, Shanghai 200135, China.
authors.forename: Hong-Di
authors.initials: HD
authors.lastname: He
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data; D004784:Environmental Monitoring; D017709:Fractals; D006723:Hong Kong; D052638:Particulate Matter / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
keywords: Lasting effect; Long-term correlation; Multifractality; Particulate matter; Vehicular emission