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Traffic related air pollution with emphasis on particle associated polycyclic aromatic hydrocarbons: Tire wear and biodiesel exhaust emissions
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.ORCID iD: 0000-0002-1598-7093
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Particulate matter (PM) is regarded as one of the more important components of air pollution causing adverse health effects. A large group of compounds associated with PM are polycyclic aromatic compounds (PACs) which comprises polycyclic aromatic hydrocarbons (PAHs). Several PACs are known for their mutagenic and carcinogenic properties as well as have the ability to induce oxidative stress.

With the growing importance of non-exhaust particles relative to vehicular tail-pipe emissions in urban air, it is necessary to investigate the possible contribution of PAHs from the different non-exhaust sources, as these inputs are far less characterized than tail-pipe emissions and their impact on human health is largely unknown.

In this thesis automobile tires, an important non-exhaust traffic related source to particles, have been investigated for its content of highly carcinogenic dibenzopyrene isomers. In a separate study benzothiazoles, a class of compounds used as vulcanization accelerators in tire manufacture, were determined to evaluate their use as potential markers for tire wear particles in ambient air.

Analysis of the tires showed a substantial variation in the PAH content between different makes of tires, likewise did the benzothiazoles content vary. By determining benzothiazole in air particles collected at a busy street in Stockholm the tire rubber contribution to airborne particles was estimated to 0.7 and 5.5 % for PM10 and all airborne particles, respectively. Together with the determined content of dibenzopyrenes and the relatively low mass contribution of tire wear to airborne particles in the urban air, estimated in this thesis as well as suggested by the literature, tire wear appears to be a minor traffic related contributor of these PAH compounds in the urban air. Nevertheless, tire wear may be an important source to 2-mercaptobenzothiazole in the urban air.

Biodiesel, a biofuel produced from plant and animal fats, has been suggested as a suitable replacement for conventional petroleum based diesel fuels. While the majority of studies have focused on health outcomes from petroleum diesel exhaust exposure, human health effects related to biodiesel exhaust exposure is much less investigated.

Biodiesel exhaust particles have been compared with conventional petroleum diesel by determining >40 PAHs in two separate studies on two different diesel engines, running on neat rapeseed methyl ester (RME), petroleum diesel and a fuel blend of 3:7 RME : petroleum diesel. One of the biodiesel studies also included determination of four oxygenated PAHs (Oxy-PAHs).

The exhaust from biodiesel combustion differed from petroleum diesel combustion with regards to particle size, number of emitted particles, relative amount of volatile material adsorbed on the particles and emission of particle-associated PAHs and Oxy-PAHs. A portion of these volatile compounds originated from unburned or partially combusted biodiesel fuel, which interfered with the analysis. A sample cleanup method was therefore developed for determination of PAH in lipid rich matrices. Biodiesel combustion produced lower emission of PAHs and Oxy-PAH with the exception of a few PAHs with higher molecular weights. In comparison with petroleum diesel, the biodiesel particles had a higher relative composition of PAHs with more than four rings. 

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University , 2016.
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-128859ISBN: 978-91-7649-374-8 (print)OAI: oai:DiVA.org:su-128859DiVA: diva2:917324
Public defence
2016-05-25, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.

Available from: 2016-05-02 Created: 2016-04-06 Last updated: 2017-02-24Bibliographically approved
List of papers
1. Automobile Tires-A Potential Source of Highly Carcinogenic Dibenzopyrenes to the Environment
Open this publication in new window or tab >>Automobile Tires-A Potential Source of Highly Carcinogenic Dibenzopyrenes to the Environment
2012 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, no 6, 3326-3334 p.Article in journal (Refereed) Published
Abstract [en]

Eight tires were analyzed for 15 high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAN), using pressurized fluid extraction. The variability of the PAIR concentrations determined between different tires was large; a factor of 22.6 between the lowest and the highest. The relative abundance of the analytes was quite similar regardless of tire. Almost all (92.3%) of the total extractable PAH content was attributed to five PAHs: benzo[ghi]perylene, coronene, indeno[1,2,3-cd]pyrene, benzo[e]pyrene, and benzo[a]pyrene. The difference in the measured PAIR content between summer and winter tires varied substantially across manufacturers, making estimates of total vehicle fleet emissions very uncertain. However, when comparing different types of tires from the same manufacturer they had significantly (p = 0.05) different PAH content. Previously, there have been no data available for carcinogenic dibenzopyrene isomers in automobile tires. In this study, the four dibenzopyrene isomers dibenzo[a,l]pyrene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene, and dibenzo[a,h]pyrene constituted <2% of the sum of the 15 analyzed HMW PAHs. These findings show that automobile tires may be a potential previously unknown source of carcinogenic dibenzopyrenes to the environment.

National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-76132 (URN)10.1021/es204257d (DOI)000301630200038 ()
Note

4

Available from: 2012-05-10 Created: 2012-05-09 Last updated: 2017-08-18Bibliographically approved
2. Particulate associated polycyclic aromatic hydrocarbon exhaust emissions from a portable power generator fueled with three different fuels – A comparison between petroleum diesel and two biodiesels
Open this publication in new window or tab >>Particulate associated polycyclic aromatic hydrocarbon exhaust emissions from a portable power generator fueled with three different fuels – A comparison between petroleum diesel and two biodiesels
Show others...
2014 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 115, 573-580 p.Article in journal (Refereed) Published
Abstract [en]

The fuel impact on the emission of more than 40 particulate associated polycyclic aromatic hydrocarbons (PAHs) in the molecular weight range 178–302 Da were investigated. The fuels; neat diesel (EN 590), rape seed methyl ester (B100) and a 30% w/w blend thereof (B30) were tested on a portable power generator without any exhaust aftertreatment. Gaseous emissions of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) were measured along with particulate emissions and its size distribution for the different fuels. Collected diesel particles were extracted using pressurized fluid extraction and analyzed using an online hyphenated liquid chromatography–gas chromatography–mass spectrometry system.

The neat B100 and the B30 fuel produced less CO and total PAHs while the emissions of NOx and particulate matter increased compared with petroleum diesel fuel per kW h. The reduction of PAH emissions of the alternative diesel fuels were 36% and 70% for B30 and B100 respectively. While the PAH profiles for the neat diesel fuel and B30 were similar, the profile of B100 differed in the sense that the emission contained a higher percentage of PAHs with higher molecular weights. The emission of these PAHs was however larger using the neat diesel fuel with the exception for some of these higher molecular weight PAHs of which there was an increased emission using B100. Thermogravimetric analysis revealed that the collected particles from B100 contained a substantial amount of volatile components. A mass spectrometric full scan analysis suggests that these volatile components are in fact unburned or partially-burned fuel constituents.

It is concluded that the particles originating from biodiesel combustion might be very different from those originating from petroleum diesel combustion which places new demands on the development of measurement methodologies originally developed for particulate emissions from petroleum-based fuels.

Keyword
PAH, Diesel, Biodiesel, RME, FAME
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-93368 (URN)10.1016/j.fuel.2013.07.062 (DOI)000325647000064 ()
Available from: 2013-08-01 Created: 2013-09-09 Last updated: 2017-06-21Bibliographically approved
3. Tire tread wear particles in ambient air—a previously unknown source of human exposure to the biocide 2-mercaptobenzothiazole
Open this publication in new window or tab >>Tire tread wear particles in ambient air—a previously unknown source of human exposure to the biocide 2-mercaptobenzothiazole
2014 (English)In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 21, no 19, 11580-11586 p.Article in journal (Refereed) Published
Abstract [en]

Urban particulate matter (PM), asphalt, and tire samples were investigated for their content of benzothiazole and benzothiazole derivates. The purpose of this study was to examine whether wear particles, i.e., tire tread wear or road surface wear, could contribute to atmospheric concentrations of benzothiazole derivatives. Airborne particulate matter (PM10) sampled at a busy street in Stockholm, Sweden, contained on average 17 pg/m3 benzothiazole and 64 pg/m3 2-mercaptobenzothiazole, and the total suspended particulate-associated benzothiazole and 2-mercaptobenzothiazole concentrations were 199 and 591 pg/m3, respectively. This indicates that tire tread wear may be a major source of these benzothiazoles to urban air PM in Stockholm. Furthermore, 2-mercaptobenzothiazole was determined in urban air particulates for the first time in this study, and its presence in inhalable PM10 implies that the human exposure to this biocide is underestimated. This calls for a revision of the risk assessments of 2-mercaptobenzothiazole exposure to humans which currently is limited to occupational exposure.

Keyword
Benzothiazole, 2-Mercaptobenzothiazole, Tire tread wear, Urban air PM10, Biocide, Humane exposure
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-104499 (URN)10.1007/s11356-014-3131-1 (DOI)000342416400046 ()
Available from: 2014-06-11 Created: 2014-06-11 Last updated: 2017-06-21Bibliographically approved
4. Class separation of lipids and polycyclic aromatic hydrocarbons in normal phase high performance liquid chromatography - A prospect for analysis of aromatics in edible vegetable oils and biodiesel exhaust particulates
Open this publication in new window or tab >>Class separation of lipids and polycyclic aromatic hydrocarbons in normal phase high performance liquid chromatography - A prospect for analysis of aromatics in edible vegetable oils and biodiesel exhaust particulates
2014 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1360, 39-46 p.Article in journal (Refereed) Published
Abstract [en]

The retention characteristics of the major lipid components in biodiesels and edible oils as well as representative polycyclic aromatic compounds (PAHs) have been investigated on five different normal phase HPLC stationary phases, in order to optimize class separation for an automatized online HPLC cleanup of PAHs prior GC-MS analysis. By stepwise comparison of different hexane/MTBE compositions as mobile phases on cyano-, phenyl-, pentabromobenzyl-, nitrophenyl- and amino- modified silica columns, the capacity and selectivity factors for each analyte and column could be calculated. It was concluded that the most suitable column for backflush isolation of PAHs in biodiesel and edible oil matrices was the pentabromobenzyl-modified silica (PBB). A previously described online HPLC-GC-MS system using the PBB column was then evaluated by qualitative and quantitative analysis of a biodiesel exhaust particulate extract and a vegetable oil reference material. The GC-MS full scan analysis of the biodiesel particulate extract showed that the lipids had been removed from the sample and a fraction containing PAHs and oxygenated derivatives thereof had been isolated. Quantified mass fractions of PAHs of the reference material BCR-458 agreed well for most of the certified PAH mass fractions in the spiked coconut oil reference material.

Keyword
Biodiesel particulates, Edible oils, Fatty acid methyl esters, Sample cleanup, High performance liquid chromatography
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-106272 (URN)10.1016/j.chroma.2014.07.064 (DOI)000341469400005 ()
Available from: 2014-07-29 Created: 2014-07-29 Last updated: 2017-12-05Bibliographically approved
5. Physical and chemical properties of RME biodiesel exhaust particles without engine modifications
Open this publication in new window or tab >>Physical and chemical properties of RME biodiesel exhaust particles without engine modifications
Show others...
2016 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 186, 102 p.261-269 p.Article in journal (Refereed) Published
Abstract [en]

A major contributor to ambient particulate air pollution is exhaust from diesel engines and other vehicles,which can be linked to different adverse health effects. During the last decades, a global drive towardsfinding sustainable and clean bio-based alternative fuels for the transport sector has taken place and biodieselis one of the most established alternatives today. To better assess the overall effects on a publichealth level when introducing biodiesel and other renewable fuels, a better understanding of the detailedexhaust particle properties, is needed. In this work, the physical and chemical properties of biodieselexhaust particles were studied in comparison to standard diesel exhaust emissions, in an existing enginewithout modifications, focusing on particulate carbonaceous matter and PAH/Oxy-PAH as well as fineparticle size distribution. An older off-road engine, produced between 1996 and 2004, was used withthree different fuels/fuel blends; (1) 100 wt% low-sulfur standard petro diesel (SD), (2) 100 wt% rapeseedmethyl ester biodiesel (B100) and (3) a blended fuel – B30 consisting of 30 wt% RME and 70 wt% SD. Thestudy focused mainly on emissions from transient engine operation, but includes also idling conditions.The gaseous emissions measured for the biodiesel fuel were in general in accordance with previousreported data in the literature, and compared to the standard petro diesel the emissions of CO was lowerwhile NOx emissions increased. The particulate mass concentration during transient operation wasalmost halved compared to when petro diesel was used and this was associated with a decrease in averageparticle size. The shift in particle mass and size was associated with a higher fraction of organic matterin general, considerable less PAH’s but a relative higher fraction of Oxy-PAH’s, when shifting frompetro diesel to biodiesel.

Publisher
102 p.
Keyword
Biodiesel, RME, Diesel engine, Exhaust emissions, Particles characteristics, PAH
National Category
Chemical Engineering
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-128855 (URN)10.1016/j.fuel.2016.08.062 (DOI)000385318600027 ()
Available from: 2016-05-12 Created: 2016-04-05 Last updated: 2017-11-30Bibliographically approved

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