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  • 1.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Abbasi, Saeed
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Indoor and outdoor measurement of airborne particulates on a commuter train running partly in tunnels2018In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 232, no 1, p. 3-13Article in journal (Refereed)
    Abstract [en]

    Wear processes from mechanical braking, rail/wheel contact, the railway electrification system and re-suspended materials due to the turbulence of passing trains in tunnels and stations have been suggested to be the main contributors to particulate matter levels inside trains. In this study, onboard monitoring was performed on a commuter train stopping at underground and aboveground stations. The concentration and size distribution of particulates were monitored for both indoor and outdoor levels. The results show that the levels of PM10 and PM2.5 inside the train were about one-fifth of the outdoor levels. Significant increases in indoor particulate number concentrations were observed in tunnel environments and there was a slight increase when the doors were open. Differences in the size distributions of micro- and nano-sized particulates could be identified for different tunnels.

  • 2.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Hedberg, Yolanda
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Karolinska Institutet, Sweden.
    Mei, Nanxuan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Airborne Wear Particles Generated from Conductor Rail and Collector Shoe Contact: Influence of Sliding Velocity and Particle Size2016In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 64, no 3, article id 40Article in journal (Refereed)
    Abstract [en]

    The mechanical wear of train components is one of the main sources of airborne particles in subway air. A certain contribution is suspected to derive from third-rail systems due to the sliding of two metallic surfaces between conductor rail and collector shoe during operation. In this study, a pin-on-disc apparatus was used to simulate the friction between such two sliding partners (shoe-to-rail). Airborne particles generated from the sliding contact were measured by particle counters (a fast mobility particle sizer spectrometer and an optical particle sizer) and were collected by an electrical low-pressure impactor for physical and chemical analysis. Interface temperature for each test was measured by a thermocouple. The influence of sliding velocity and temperature on particulate number concentration, size distribution, and chemical composition was investigated. Atomic absorption spectroscopy, cyclic voltammetry, and energy-dispersive spectroscopy measurements were carried out to determine the chemical compositions. Results show that increasing sliding velocity results in a higher temperature at the frictional interface and a higher concentration of ultrafine particles. The ratio of manganese to iron surface oxides increased strongly with smaller particle size. A copper compound was observed in some particle samples, probably gerhardite (Cu2NO3(OH)(3)) formed due to high temperature.

  • 3.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Effective density of airborne particles in a railway tunnel from field measurements of mobility and aerodynamic size distributions2018In: Aerosol Science and Technology, ISSN 0278-6826, E-ISSN 1521-7388, Vol. 52, no 8, p. 886-899Article in journal (Refereed)
    Abstract [en]

    The objective of this study is to investigate the particle effective density of aerosol measurements in a railway tunnel environment. Effective density can serve as a parameter when comparing and calibrating different aerosol measurements. It can also be used as a proxy parameter reflecting the source of particles. Effective density was determined using two different methods. Method one defined it by the ratio of mass concentration to apparent volume size distribution. Method two relied on a comparison of aerodynamic and mobility diameter size distribution measurements. The aerodynamic size range for method one was 0.006–10 µm, and for method two, it was 10–660 nm. Using the first method, a diurnal average value of about 1.87 g/cm3 was observed for the measurements with tapered element oscillating microbalance (TEOM) in tandem with aerodynamic particle sizer + scanning mobility particle sizer (SMPS), and 1.2 g/cm3 for the combination of TEOM with electrical low pressure impactor plus (ELPI+) in the presence of traffic. With method two, the effective density was 1.45 g/cm3 estimated from the size distribution measurements with ELPI + and fast mobility particle sizer (FMPS), and 1.35 g/cm3 from ELPI + in tandem with SMPS. With both calculation methods, the effective density varied for conditions with and without traffic, indicating different sources of particles. The proportion of particles with small sizes (10–660 nm) had a significant effect on the value of the effective density when no traffic was operating. The responses of different instruments to the railway particle measurements were also compared.

  • 4.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Gustafsson, M.
    Johansson, C.
    On Particulate Emissions from Individual Trains in Tunnel Environments2016In: Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance, Dun Eaglais, Kippen Stirlingshire, FK8 3DY, UK: Civil-Comp Press , 2016Conference paper (Refereed)
  • 5.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Gustafsson, M.
    Johansson, C.
    On particulate emissions from moving trains in a tunnel environment2018In: Transportation Research Part D: Transport and Environment, ISSN 1361-9209, E-ISSN 1879-2340, Vol. 59, p. 35-45Article in journal (Refereed)
    Abstract [en]

    Increasing attention is being paid to airborne particles in railway environments because of their potential to adversely affect health. In this study, we investigate the contribution of moving trains to both the concentration and size distribution of particles in tunnel environments. Real-time measurements were taken with high time-resolution instruments at a railway station platform in a tunnel in Stockholm in January 2013. The results show that individual trains stopping and starting at the platform substantially elevate the particulate concentrations with a mobility diameter greater than 100 nm. Two size modes of the particulate number concentrations were obtained. A mode of around 170 nm occurs when a train moves, while the other mode peaks at about 30 nm when there is no train in the station. By using principal component analysis (PCA), three contributing sources were identified on the basis of the classification of the sizes of the particles, namely railway-related mechanical wear, suspension due to the movement of trains and sparking of electric-powered components. It is concluded that the particulate matter released by individual moving trains is a key contributor to fine particles (100–500 nm) on the railway platform in a tunnel.

  • 6.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Tu, Minghui
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Bergstedt, Edwin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Carlsson, Peter
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Lyu, Yezhe
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Silvergren, Sanna
    Elmgren, Max
    Hurkmans, Jennie
    Norman, Michael
    Ombordmätningar av luftburna partiklar i X60 samt på citybanans plattformar2018Report (Other (popular science, discussion, etc.))
  • 7.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Tu, Minghui
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Elmgren, Max
    SLB-analys, Environment and Health Administration, Stockholm, Sweden.
    Silvergren, Sanna
    SLB-analys, Environment and Health Administration, Stockholm, Sweden.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Factors affecting the exposure of passengers, service staff and train drivers inside trains to airborne particles2018In: Environmental Research, ISSN 0013-9351, E-ISSN 1096-0953, Vol. 166, p. 16-24Article in journal (Refereed)
    Abstract [en]

    This study investigated train air conditioning filters, interior ventilation systems, tunnel environments and platform air quality as factors affecting the concentrations of airborne particles inside trains and provides information on the exposure of passengers, train drivers and service staff to particles. Particle sampling was done inside the passenger cabin, the driver cabin and the service staff cabin during on-board measurement campaigns in 2016 and 2017. The results show that interior ventilation plays a key role in maintaining cleaner in-train air. Noticeable increases in PM10 and PM2.5 levels were observed for all of the measured cabins when the train was running in the newly opened tunnel. The increases occurred when the doors of the passenger cabin and the service staff cabin were open at underground stations. The door to the driver cabin, which remained closed for the entire measurement period, acted as a filter for coarse particles (PM2.5–10). The highest particle exposure occurred in the passenger cabin, followed by the service staff cabin, while the driver had the lowest exposure. The highest deposition dose occurs for the service staff and the lowest for commuters.

  • 8.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Tu, Minghui
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Elmgren, Max
    Silvergren, Sanna
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Variation in Airborne Particulate Levels at a Newly Opened Underground Railway Station2019In: Aerosol and Air Quality Research, ISSN 1680-8584, E-ISSN 2071-1409, Vol. 19, no 4, p. 737-748Article in journal (Refereed)
    Abstract [en]

    The construction of a new railway tunnel for commuter trains in Stockholm was completed in 2017. It included two modern stations (Odenplan and Stockholm City) with platform screen doors (PSD) and one old station (Stockholm Sodra) without PSDs. This study evaluates the concentrations of airborne particulates at the new Odenplan station, focusing on the effects of traffic operation, system age and train movement. For comparison, the other two stations in the tunnel and an above-ground railway station (Solna) were also investigated. The new platform was clean prior to opening for traffic (the average concentration of PM10 and PM2.5 was 12 and 2 mu g m(-3), respectively). Substantial increases in the PM10 and PM2.5 levels were observed after it came into service, with the average concentrations increasing to 120 and 30 mu g m(-3) after 1 week and then to 175 and 35 mu g m(-3) after 3 months of operation. The train movement factor (traffic frequency and train stopping period) was found to have a strong effect on the coarse-sized particle concentrations (0.3-10 mu m). Comparable levels of PM10 and PM2.5 were measured at both the new Odenplan station and the old station, where the amount of traffic was similar. For the other new station, Stockholm City, where traffic was only half as frequent, the PM10 and PM2.5 levels were substantially lower.

  • 9.
    Cha, Yingying
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Tu, Minghui
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Elmgren, Max
    SLB-analys, Environment and Health Administration, Stockholm, Sweden.
    Silvergren, Sanna
    SLB-analys, Environment and Health Administration, Stockholm, Sweden.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Variation of airborne particulate levels in a newly built railway tunnel2018In: Aerosol and Air Quality Research, ISSN 1680-8584, E-ISSN 2071-1409Article in journal (Other academic)
    Abstract [en]

    The construction of a new railway tunnel for commuter trains in Stockholm was completed in 2017. It included two modern stations (Odenplan and Stockholm City) with platform screen doors (PSD) and one old station (Stockholm Södra) without PSDs. This study evaluates the concentrations of airborne particulates for the new stations, focussing on the effects of traffic operation, system age and train movement. For comparison, the other old station in the tunnel and an above-ground railway station (Solna) were also investigated. The new Odenplan platform was clean before its opening for traffic (12 and 2 μg/m3 for average PM10 and PM2.5, respectively). Substantial increases in the PM10 and PM2.5 concentrations were observed after it came into service. The average levels of PM10 and PM2.5 increased to 120 and 30 μg/m3 after one week of operation, and increased again to 175 and 35 μg/m3 after 3 months. The train movement factor (traffic frequency and train stop period) was found to have a strong effect on the particle concentrations of coarse sizes (0.3–10 μm). Comparable levels of PM10 and PM2.5 were measured at both the new station and the old station where the traffic frequency was similar. For the other new station, which had half the traffic frequency due to the station design with two separate platforms, the PM10 and PM2.5 levels were substantially lower.

  • 10.
    Liu, Hailong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Cha, Yingying
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Jonsson, Lage Tord Ingemar
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of the Sliding Velocity on the Size and Amount of Airborne Wear Particles Generated from Dry Sliding Wheel-Rail Contacts2016In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 63, no 3, article id 30Article in journal (Refereed)
    Abstract [en]

    A set of frictional experiments have been conducted on a pin-on-disk apparatus to investigate the effect of the sliding velocity on airborne wear particles generated from dry sliding wheel-rail contacts. The size and the amount of generated particles were acquired by using particle counter instruments during the whole test period. After the completion of tests, the morphology and chemical compositions of pin worn surfaces and collected particles were analyzed by using scanning electron microscopy combined with an energy-dispersive X-ray analysis system. The results show that the total particle number concentration increases dramatically with an increased sliding velocity from 0.1 to 3.4 m/s. Moreover, the fine and ultrafine particles (<1 mu m) dominates the particle generation mode in the case of a high sliding velocity (1.2 and 3.4 m/s). The contact temperature variation is observed to be closely related to the size mode of the particle generation. In addition, the sliding velocity is found to influence the active wear. Correspondingly, an oxidative wear is identified as the predominant wear mechanisms for cases with high sliding velocities (1.2 and 3.4 m/s). This produces a substantial number of iron oxide-containing particles (<1 mu m) and reduces the wear rate to a relative low level (the wear rate for a 3.4 m/s sliding velocity is 4.5 % of that for a 0.4 m/s sliding velocity).

  • 11.
    Tu, Minghui
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Cha, Yingying
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Wahlström, Jens
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Towards a two-part train traffic emission factors model for airborne wear particlesManuscript (preprint) (Other academic)
  • 12.
    Tu, Minghui
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Cha, Yingying
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Wahlström, Jens
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Towards a two-part train traffic emissions factor model for airborne wear particles2019In: Transportation Research Part D: Transport and Environment, ISSN 1361-9209, E-ISSN 1879-2340, Vol. 67, p. 67-76Article in journal (Refereed)
    Abstract [en]

    In 2017 a new railway tunnel containing two stations opened in Stockholm, Sweden. A series of field measurements were carried out on the platforms in this tunnel before and after it was opened for normal traffic. These measurements were used to investigate the contribution of airborne particle emissions from wear processes to total train emissions. This field data was used to develop a two-part train traffic emission factor model for PM10. The two parts are the accumulative effect term (relating to operating distance such as wheel-rail contact and overhead electric line sliding contact) and a brake effect term (relating to the number of braking operations such as brake disc and brake pad contact). The results show that operating a single trial train at a higher than normal frequency on an otherwise empty platform increases the platform particulate concentration until the concentration reaches a steady value. The model suggests that brake emissions account for about 50% of the total emissions measured in the tunnels.

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