Tyre wear particles in the near-road environment of a Swedish highway: Characterisation of concentrations and transport dynamics across snow, soil and through a stormwater system
Doctoral thesis, 2025
Tyre wear particles (TWP) are increasingly recognised as a major source of microplastic pollution in urban environments, particularly in areas with high traffic intensity. Several laboratory studies suggest toxic effects from TWP and chemical compounds found in tyres, that can leach into aquatic environments. However, the occurrence of TWP in various environmental compartments remains poorly quantified, especially in the finer size fraction <20 µm. This thesis investigates the environmental concentrations, transport pathways, and morpho-chemical characteristics of TWP in the near-road environment of a Swedish highway. TWP were quantified across multiple environmental compartments—snow, soil, stormwater, sediments, and recipient waters—with special attention to the fine fraction (<20 µm). The methodology employed for the analysis of the samples was a quantification of styrene-butadiene rubbers with pyrolysis-gas chromatography-mass spectrometry using a combination of marker compounds (benzene, α-methylstyrene, ethylstyrene, and butadiene trimer) followed by Monte Carlo simulations for calculation of TWP concentrations. The work in this thesis also includes quantification of other microplastic polymers in stormwater and detailed morphological and chemical characterisation of TWP in snow. TWP were consistently detected in all sampled compartments (snow, soil, stormwater, recipient waters and sediments) confirming their widespread distribution. Elevated concentrations were found in roadside snow and in stormwater during rain, with limited retention observed in the stormwater system. Fine particles (1.6–20 µm) represented a substantial proportion of total TWP, particularly in runoff, highlighting their relevance for monitoring and treatment.
Microplastic analyses revealed polyethylene, polypropylene and rubber polymers as the most common polymers in runoff from highway stormwater system. Correlation analyses showed strong associations between TWP and suspended solids, organic content, and metals in waterborne sample matrices, while more complex behaviours were observed in soil. These findings provide new insights into TWP dynamics and support more effective risk assessment and mitigation strategies.
Microplastic analyses revealed polyethylene, polypropylene and rubber polymers as the most common polymers in runoff from highway stormwater system. Correlation analyses showed strong associations between TWP and suspended solids, organic content, and metals in waterborne sample matrices, while more complex behaviours were observed in soil. These findings provide new insights into TWP dynamics and support more effective risk assessment and mitigation strategies.
SEM-EDX
Snow
Road runoff
Pyrolysis-gc/ms
Tire and road wear
Stormwater pollutants
Automatic sequential sampling
Soil
Gully pot
Microplastics
Author
Elly Lucia Gaggini
Chalmers, Architecture and Civil Engineering, Water Environment Technology
Characterisation and spatial distribution of tyre wear particles in Swedish highway snow: Loads into roadside ditches and risk of emissions with snowmelt
Environmental Challenges,;Vol. 20(2025)
Journal article
Tyre wear particles and metals in highway roadside ditches: Occurrence and potential transport pathways
Environmental Pollution,;Vol. 372(2025)
Journal article
Assessment of fine and coarse tyre wear particles along a highway stormwater system and in receiving waters: Occurrence and transport
Journal of Environmental Management,;Vol. 367(2024)
Journal article
Gaggini, E.L., Sokolova, E., Rødland, E.S., Strömvall, A.-M., Andersson-Sköld, Y., Bondelind, M., Tyre wear particles in a highway stormwater system during rain: quantification by automatic sampling and Pyrolysis-GC/MS and correlations with metals, solids and turbidity
Gaggini, E.L., Strömvall, A.-M., Rødland, E., Sokolova, E.S., Andersson-Sköld, Y., Bondelind, M., 2025. Microplastics in a highway stormwater system: concentrations and variability during rainfall
Höga halter mikroplaster från däck i dagvatten och snö vid svensk motorväg
Mikroplaster från däckslitage har uppmärksammats som en betydande föroreningskälla i trafikerade områden och i Sverige beräknas utsläppen till 11 000 ton per år. Laboratorie-studier har visat att partiklarna kan vara skadliga för vattenlevande organismer, men kunskapen om deras förekomst och påverkan i naturliga miljöer är fortfarande begränsad, särskilt för de allra minsta partiklarna under 20 mikrometer.
I denna avhandling har däckslitagepartiklar undersökts i vägnära miljöer längs en motorväg i Sverige. Partiklarna förekom i alla undersökta miljöer: snö, jord i diken, vatten och sediment längs ett dagvattensystem, och i ett närliggande vattendrag. Särskilt höga halter fanns i snö nära vägen och i dagvatten provtaget under regn. Detta tyder på att däckslitagepartiklarna transporteras vidare från vägbanan och genom dagvattensystemet vid nederbörd, och att smältvatten från snö kan orsaka höga utsläpp.
En stor del av partiklarna hittades i den mindre storleksfraktionen och dessa riskerar att spridas vidare ut i vattendrag eftersom de är svårare att fånga upp i konventionella dagvattensystem med rännstensbrunnar. Både snö och dikesprover visade att halterna av däckslitagepartiklar avtog med vägavstånd, vilket pekar på att åtgärder nära väg kan vara effektiva.
Även andra typer av mikroplaster analyserades i dagvattnet, vilket bekräftade att däckslitagepartiklar var den vanligaste typen av mikroplast i denna vägmiljö. Sammantaget ger resultaten ny kunskap om hur mikroplaster sprids i vägnära miljöer och visar på behovet av fortsatt övervakning, riskbedömning och åtgärder för att minska utsläppen och skydda känsliga vattenmiljöer.
Mikroplaster från däckslitage har uppmärksammats som en betydande föroreningskälla i trafikerade områden och i Sverige beräknas utsläppen till 11 000 ton per år. Laboratorie-studier har visat att partiklarna kan vara skadliga för vattenlevande organismer, men kunskapen om deras förekomst och påverkan i naturliga miljöer är fortfarande begränsad, särskilt för de allra minsta partiklarna under 20 mikrometer.
I denna avhandling har däckslitagepartiklar undersökts i vägnära miljöer längs en motorväg i Sverige. Partiklarna förekom i alla undersökta miljöer: snö, jord i diken, vatten och sediment längs ett dagvattensystem, och i ett närliggande vattendrag. Särskilt höga halter fanns i snö nära vägen och i dagvatten provtaget under regn. Detta tyder på att däckslitagepartiklarna transporteras vidare från vägbanan och genom dagvattensystemet vid nederbörd, och att smältvatten från snö kan orsaka höga utsläpp.
En stor del av partiklarna hittades i den mindre storleksfraktionen och dessa riskerar att spridas vidare ut i vattendrag eftersom de är svårare att fånga upp i konventionella dagvattensystem med rännstensbrunnar. Både snö och dikesprover visade att halterna av däckslitagepartiklar avtog med vägavstånd, vilket pekar på att åtgärder nära väg kan vara effektiva.
Även andra typer av mikroplaster analyserades i dagvattnet, vilket bekräftade att däckslitagepartiklar var den vanligaste typen av mikroplast i denna vägmiljö. Sammantaget ger resultaten ny kunskap om hur mikroplaster sprids i vägnära miljöer och visar på behovet av fortsatt övervakning, riskbedömning och åtgärder för att minska utsläppen och skydda känsliga vattenmiljöer.
High concentrations of microplastics originating from tyre wear in runoff and snow by a Swedish highway
Microplastics from tyre wear have been identified as a major source of pollution in areas with heavy traffic, and in Sweden, the yearly emissions are estimated at around 11,000 tonnes. Laboratory studies have shown that these particles can be harmful to aquatic life, but our understanding of their presence and impact in real-world environments is still limited—especially when it comes to the finest particles, smaller than 20 micrometres.
This thesis examined tyre wear particles in roadside environments along a Swedish motorway. The particles were found in all types of environments studied: snow, soil in roadside ditches, water and sediment in a stormwater system, and in a nearby stream. Particularly high levels were found in snow close to the road and in stormwater sampled during rainfall. This suggests that tyre wear particles are carried away from the road surface during rain, making their way through the stormwater system, and that snowmelt could lead to large emissions into the environment.
Many of the particles were found in the smallest size fraction, which poses a problem since these are harder to trap in simple stormwater systems drained by gully pots, and are therefore more likely to reach natural water bodies. Both snow and soil samples showed that the levels of tyre wear particles decreased with distance from the road, indicating that roadside measures could be effective.
Other types of microplastics were also analysed in the stormwater, confirming that tyre wear particles were the most common kind in this road environment. Altogether, the findings offer new insights into how microplastics spread near roads and highlight the need for continued monitoring, risk assessments, and actions to reduce emissions and protect sensitive aquatic ecosystems.
Microplastics from tyre wear have been identified as a major source of pollution in areas with heavy traffic, and in Sweden, the yearly emissions are estimated at around 11,000 tonnes. Laboratory studies have shown that these particles can be harmful to aquatic life, but our understanding of their presence and impact in real-world environments is still limited—especially when it comes to the finest particles, smaller than 20 micrometres.
This thesis examined tyre wear particles in roadside environments along a Swedish motorway. The particles were found in all types of environments studied: snow, soil in roadside ditches, water and sediment in a stormwater system, and in a nearby stream. Particularly high levels were found in snow close to the road and in stormwater sampled during rainfall. This suggests that tyre wear particles are carried away from the road surface during rain, making their way through the stormwater system, and that snowmelt could lead to large emissions into the environment.
Many of the particles were found in the smallest size fraction, which poses a problem since these are harder to trap in simple stormwater systems drained by gully pots, and are therefore more likely to reach natural water bodies. Both snow and soil samples showed that the levels of tyre wear particles decreased with distance from the road, indicating that roadside measures could be effective.
Other types of microplastics were also analysed in the stormwater, confirming that tyre wear particles were the most common kind in this road environment. Altogether, the findings offer new insights into how microplastics spread near roads and highlight the need for continued monitoring, risk assessments, and actions to reduce emissions and protect sensitive aquatic ecosystems.
Microplastics in road runoff: occurrence, properties and transport modelling
Norwegian Public Roads Administration (NPRA) (B11191 Ferjefri E39), 2020-01-01 -- 2024-12-31.
Formas (2019-00284), 2020-01-01 -- 2022-12-31.
Subject Categories (SSIF 2025)
Environmental Sciences
Water Engineering
ISBN
978-91-8103-257-4
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5715
Publisher
Chalmers