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Traffic Aerosol emission velocity derived from direct flux measurements over urban Stockholm, Sweden
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
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2011 (English)In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 45, no 32, 5725-5731 p.Article in journal (Refereed) Published
Abstract [en]

Size-resolved aerosol vertical number fluxes were measured using the eddy covariance method, 105 meters above the ground over the city of Stockholm, Sweden, between 1st April 2008 and 15th April 2009. The size range of the measurements cover particles from 0.25 to 2.5 μm diameter (Dp). Emission velocities (ve) were calculated for the same size range and were found to be well correlated with friction velocity (u*) and CO2 fluxes (FCO2). These variables were used to parameterize the emission velocity aswhere ve and u* are given in [m s−1], Dp in [μm], and FCO2 in [mmol m−2s−1].

The parameterization reproduces the average diurnal cycle from the observations well for particles sizes up to 0.6 μm Dp. For larger particles the parameterization tends to over predict the emission velocity. These larger particles are not believed to be produced by combustion and therefore not well represented by FCO2, which represents the traffic source through its fossil fuel consumption and the related CO2 emissions.

Place, publisher, year, edition, pages
2011. Vol. 45, no 32, 5725-5731 p.
Keyword [en]
Primary aerosol emissions, Carbon dioxide emissions, Traffic aerosol, Urban aerosol, Traffic activity, Emission factors, Eddy covariance, Aerosol flux
National Category
Natural Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-61685DOI: 10.1016/j.atmosenv.2011.07.026ISI: 000295607300009OAI: oai:DiVA.org:su-61685DiVA: diva2:437035
Available from: 2011-08-26 Created: 2011-08-26 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Traffic Emissions of Aerosols
Open this publication in new window or tab >>Traffic Emissions of Aerosols
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Non-exhaust traffic emissions are unregulated, yet the mass emission of non-exhaust particles may be larger than exhaust emissions. In addition, their emission factors (EF) are more uncertain than exhaust emissions. This thesis presents aerosol flux measurements in Stockholm using the eddy covariance method. Prior to this work, no direct flux measurements using micrometeorological techniques had been performed to study non-exhaust emissions. The challenges of measuring non-exhaust emissions include low particle number concentrations and the complex meteorological influences due to the dependence on road suspension processes. A novel approach applied here is the use of simultaneous flux measurements of CO2 and particles enabling improved parameterizations and understanding of source processes. It was shown that the EF for particles in the size range 0.25 to 2.5µm diameter are only 0.1% of the total particle number EF, indicating that ultrafine particles dominate the number fluxes. Sub- and super-micron particle emissions have been quantified, characterized, and parameterized. Dependence on wind speed, road surface condition and CO2 correlation indicates that the super-micron particles are primarily emitted through wind and vehicle induced turbulence. On the other hand, good correlation between sub-micron particles and CO2 flux indicates that these particles are primary emissions from traffic. The sub-micron particles (0.25 to 0.6 µm Dp) consisted of 60% semi-volatile components and 40% of non-volatile material. For the super-micron particle emissions, clear seasonal characteristics were found with the highest average values during spring. Heavy duty vehicles were found to emit 30 times more than light duty vehicles per km. This indicates that trucks and buses are more efficient at suspending super-micron particles than light duty vehicles. These results are consistent with the hypothesis that the particles originate from abrasion of road surfaces by studded tires.

Place, publisher, year, edition, pages
Stockholm: Department of Applied Environmental Science (ITM), Stockholm University, 2011. 96 p.
Keyword
Primary Aerosol Emissions, Carbon Dioxide Emissions, Traffic Aerosol, Urban Aerosol, Traffic Activity, Emission Factors, Eddy Covariance, Aerosol Flux
National Category
Meteorology and Atmospheric Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-61673 (URN)978-91-7447-337-7 (ISBN)
Public defence
2011-09-28, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 3: In press. Paper 4: Submitted.Available from: 2011-09-06 Created: 2011-08-25 Last updated: 2011-09-07Bibliographically approved

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Vogt, MatthiasAhlm, LarsStruthers, HamishJohansson, Christer
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