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Factors controlling particle number concentration and size at metro stations.

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Bibliographic Details
Title:	Factors controlling particle number concentration and size at metro stations.
Authors:	Reche, C.¹ cristina.reche@idaea.csic.es, Moreno, T.¹, Martins, V.¹, Minguillón, M.C.¹, Jones, T.², de Miguel, E.³, Capdevila, M.³, Centelles, S.³, Querol, X.¹
Source:	Atmospheric Environment. May2017, Vol. 156, p169-181. 13p.
Subject Terms:	Air quality, Particle size distribution, Emissions (Air pollution), Ventilation, Railroad terminals -- Design & construction
Abstract:	An extensive air quality campaign was performed at differently designed station platforms in the Barcelona metro system, aiming to investigate the factors governing airborne particle number (N) concentrations and their size distributions. The study of the daily trends of N concentrations by different size ranges shows that concentrations of N 0.3–10 are closely related with the schedule of the metro service. Conversely, the hourly variation of N 0.007–10 (mainly composed of ultrafine particles) could be partly governed by the entrance of particles from outdoor emissions through mechanical ventilation. Measurements under different ventilation settings at three metro platforms reveal that the effect on air quality linked to changes in the tunnel ventilation depends on the station design. Night-time maintenance works in tunnels are frequent activities in the metro system; and after intense prolonged works, these can result in higher N concentrations at platforms during the following metro operating hours (by up to 30%), this being especially evident for N 1–10 . Due to the complex mixture of factors controlling N, together with the differences in trends recorded for particles within different size ranges, developing an air quality strategy at metro systems is a great challenge. When compared to street-level urban particles concentrations, the priority in metro air quality should be dealing with particles coarser than 0.3 μm. In fact, the results suggest that at narrow platforms served by single-track tunnels the current forced tunnel ventilation during operating hours is less efficient in reducing coarse particles compared to fine. [ABSTRACT FROM AUTHOR]
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Database:	GreenFILE

Description
Abstract:	An extensive air quality campaign was performed at differently designed station platforms in the Barcelona metro system, aiming to investigate the factors governing airborne particle number (N) concentrations and their size distributions. The study of the daily trends of N concentrations by different size ranges shows that concentrations of N 0.3–10 are closely related with the schedule of the metro service. Conversely, the hourly variation of N 0.007–10 (mainly composed of ultrafine particles) could be partly governed by the entrance of particles from outdoor emissions through mechanical ventilation. Measurements under different ventilation settings at three metro platforms reveal that the effect on air quality linked to changes in the tunnel ventilation depends on the station design. Night-time maintenance works in tunnels are frequent activities in the metro system; and after intense prolonged works, these can result in higher N concentrations at platforms during the following metro operating hours (by up to 30%), this being especially evident for N 1–10 . Due to the complex mixture of factors controlling N, together with the differences in trends recorded for particles within different size ranges, developing an air quality strategy at metro systems is a great challenge. When compared to street-level urban particles concentrations, the priority in metro air quality should be dealing with particles coarser than 0.3 μm. In fact, the results suggest that at narrow platforms served by single-track tunnels the current forced tunnel ventilation during operating hours is less efficient in reducing coarse particles compared to fine. [ABSTRACT FROM AUTHOR]
ISSN:	13522310
DOI:	10.1016/j.atmosenv.2017.03.002