An environmental indicator: particulate characteristics on pedestrian pathway along integrated urban thoroughfare in Metropolis
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Particulate matter (PM) originated by road transport constitutes an urgent task for megacities and pedestrians are supposed to be the first batch of innocent victims that exposed to and inhaled the polluted air. Footbridges have become a promising resolution to land tension, the location and design of them should be more considered in order to provide a more desirable walking system to pedestrians. In this study, three groups of PM [i.e., 0.3–0.9 μm (sub-fine), 0.9–2.5 μm (fine) and 2.5–10 μm (coarse)] were measured at different traffic scenario related footbridges (i.e., upstream of the on-ramp, downstream of the on-ramp, and signalized intersection) along an urban artery in Hong Kong, and their traffic volume composition, multifractality and cross-correlation behavior were investigated thereafter. Multifractal detrended fluctuation analysis and multifractal detrended fluctuation cross-correlation analysis were used simultaneously to quantify the persistency of different PM groups and interaction between them. The results indicate that although the particle concentration at intersection above footbridges presents the lowest, it has the highest emission rate and the strongest multifractality and cross-correlation behavior, especially the finer ones. Hence, it is suggest that the nature ventilation style of footbridges should avoid to be built above the signalized intersection due to the long persistency of particles and active interaction between different particle groups.
KeywordsFootbridges On-ramp Intersection Particulate matter Multifractality Cross-correlation
The work was partially supported by Strategic Research Grant, City University of Hong Kong Grant (SRG-7004637 and 7004867), Innovation and Technology Fund (ITF) (CityU-9678142), and National Natural Science Foundation of China (Nos. 11302125 and 11672176) and Innovation Foundation of Shanghai Municipal Ministry of Education (No. 13YZ085). Authors would like to thank the Hong Kong Observatory for providing the weather data. And the comments provided by anonymous referees are also appreciated.
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