Journal of Earth Sciences and Geotechnical Engineering

Air quality in an urban public transportation Network: Local-scale determinants

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• Abstract

   

  Air quality, in terms of particles and particulate polycyclic aromatic hydrocarbons (PAHp), is measured in urban public transport systems serving a major French conurbation. The systems comprise both conventional and dedicated public transport services (DPTS). The objective of this study is to identify determinants of the air quality inhaled by users. Mobile measurements indicate that the latter is being dictated by transport system-independent (external) and system-dependent (internal) variables or a combination thereof. The external variables consist of outdoor processes that lead to accumulating or discharging ambient particulate pollution. Internal variables, in contrast, encompass the particulate generation inside vehicles and transfer processes specific to the configuration, structure and use of public transport and related facilities. Consequently, air quality in transport services and transit stations is highly variable and quite difficult to explain by means of regional and/or urban background pollutions; it exhibits strong temporal and spatial fluctuations (when measured in seconds or meters), which in some cases are superimposed on durable trend lines (i.e. extending to tens of minutes or kilometers). This array of variables moreover results in a variety of particulate pollution, including: authigenic particles in certain DPTS, coarse particles from transport corridors, and PAHp-loaded fines from road traffic.