High levels of tire wear particles in soils along low traffic roads

Stormwater treatment in infiltration swales with an engineered and planted soil media - Results of a pilot-scale approach

Infiltration swales are well-established stormwater control measures. To meet the future multi-coded requirements, i.e. drainage safety, pollutant retention, and the promotion of biodiversity, we identified a research need regarding the soil layer and its simultaneous adaption of technical and soil functions. In particular, we aimed for higher water storage capacity and increased pollutant retention by developing engineered soil media based on natural topsoil or subsoil with amendments such as compost and brick sand. The media was flushed with real road runoff and monitored over more than two years, focusing on external influencing factors (e.g., antecedent dry-weather period, inflow rate, and de-icing salts) on pollutant retention. We found comparable water retention rates between both engineered soil media and the control but concluded that the amendment of brick sand had a beneficial impact given that the control had a considerably higher fine soil and humus content. An improvement of the retention efficiency was not achieved through the amendments compared to the control and retention efficiencies were >89 %, >97 %, and >94 % for Cu, Zn, and fine suspended solids. External factors had no dominant effect on the retention efficiency, a significant influence could only be demonstrated for organic matter. Additionally, we evaluated a minor but constant leaching for V and DOC. We concluded that engineered media may be suitable in swales through its potential higher water retention capacity with a simultaneous good retention of pollutants. However, attention must be paid to the leaching behavior of the soil amendments.

Tyre wear particles and metals in highway roadside ditches: Occurrence and potential transport pathways

Tyre wear particles (TWP) pose significant environmental concerns, necessitating a comprehensive understanding of their environmental distribution for accurate risk assessment. Roadside soil has not been extensively studied for TWP occurrence and distribution. This study aims to characterise the occurrence and distribution of TWP and associated metals in roadside soils and to investigate the correlations between these contaminants. Soil samples were collected from two road ditches along a Swedish national motorway at varying depths and distances from the contamination source. TWP in fractions <500 μm were analysed using PYR-GC/MS. Results indicated that TWP concentrations in soil samples ranged from 0.74 ± 0.20 to 12.40 ± 1.88 mg/kg d.w., consistent with other studies, and decreased with distance from the road, similar to Zn. In one ditch, TWP concentrations remained constant with depth, unlike concentrations of Co and Cr, which increased, while in the other ditch, TWP and most metals did not decrease with depth or distance from the outlet. Strong correlations were found between concentrations of TWP and Zn in one, but not the other, where Zn might have followed different transport due to leaching. Metal correlations in both ditches suggest traffic-related but not necessarily tyre wear origins. These findings are crucial for risk assessments of traffic-related pollutants, particularly TWP, and their spread into soils.

Characterisation of tyre wear particle transport from road runoff to sea in coastal environments

Data on the fate of tyre wear particles (TWPs) within aquatic environments is limited. This study quantified TWPs entering estuaries in stormwater drainage and atmospheric fallout, and once they have reached the marine environment, within surface waters and sediments. TWPs were found at concentrations of 0.4 mg/L, 2.55 mg/m2/d, 0.00063 mg/L, and 0.96 g/kg respectively. Samples were partitioned by size to examine the distribution of TWP mass. 80-90% of TWP mass entering marine systems (stormwater and atmospheric fallout) lay between 31-125 µm. Larger particles preferentially accumulated in sediments where ∼50 % of TWP mass was >250 μm, compared to surface waters where the size class 15-63 μm accounted for ∼80 %. This study provides novel data on the sizes and concentrations of TWP pollution in coastal environments. Such data are of importance in determining biological exposures. Notably, the presence of TWPs in surface waters demonstrates their potential for transport over longer distances.

Assessment of tire-derived additives and their metabolites into fruit, root and leafy vegetables and evaluation of dietary intake in Swiss adults

Tire wear particles, released at an estimated 6 million tons annually worldwide, introduce various chemical substances into agricultural environments through atmospheric deposition, road runoff, and reclaimed wastewater. These tire-derived compounds are known to impact ecosystem health. This study investigates the transfer of such additives and their metabolites into vegetables, assessing human dietary intake. Using UPLC-MS/MS, eleven tire-related compounds were analyzed in 100 vegetable samples from nine Swiss retailers, including leafy (lettuce, cabbage, spinach), root (onion, potato, carrot), and fruit (tomato, bell pepper, zucchini, pumpkin) vegetables. Contamination was detected in all vegetable varieties. 31 % of the 100 samples contained benzothiazole (BTH), 1,3-diphenylguanidine (DPG), 6-PPD, or 1,3-dicyclohexylurea (DCU) at levels exceeding the limit of quantification (LOQ) whereas blank values remained below LOD. DPG was most frequently detected (18 %, n = 100), followed by 6-PPD (15 %, n = 100), DCU (10 %, n = 100), and BTH (3 %, n = 100). Spinach comprised 78 % of DPG-positive leafy samples. Daily intakes of 6-PPDQ, DCU, 6-PPD, and DPG from vegetables were estimated at 0-18.7, 0-57.7, 0-42.3, and 0-42.4 ng/person/day, respectively. While current toxicological data suggest no immediate health concerns, significant knowledge gaps remain regarding long-term toxicity. This study offers critical insights into the presence of tire-derived substances in agriculture and underscores the need for further research to better assess environmental and human health risks.

Tire-Road-Wear Particles and Glass Beads in the Gizzard of the Endangered Terrestrial Bird, Okinawa Rail (Hypotaenidia okinawae)

This study analyzed microplastics and glass beads (GBs; an indicator of traffic-derived particulate contamination) in 42 gizzards of an endangered terrestrial bird, the Okinawa rail (Hypotaenidia okinawae). Black rubber fragments (BRs) were found in 57% of the specimens (1-184 items/individuals), and GBs were found in 48% (1-32 items/ind.). FTIR identified the rubbers as the same materials used in tire tread. A significant positive correlation was found between abundances of BRs and GBs in the gizzards (p < 0.01), suggesting the same source and exposure pathway. Large quantities of BRs, namely tire-road-wear particles (TRWPs), were also found in environmental samples (road dust, roadside soil, and side-ditch sediment) and diet organisms of the Okinawa rail (earthworm, millipede, and snail). The characteristics of these particles (appearance, material type, and size distribution) were consistent between the gizzard contents and the environmental samples. The concentration ratio of GBs and BRs in the Okinawa rail was similar to that in side-ditch sediment and diet organisms, especially earthworms. These results indicate that Okinawa rails are exposed to traffic-derived contaminants including TRWPs via ground-feeding along the roadside. To our knowledge, this is the first evidence of TRWPs exposure in terrestrial bird species.

Tire Wear Particles Exposure Enhances Denitrification in Soil by Enriching Labile DOM and Shaping the Microbial Community

Tire wear particles (TWP) are emerging contaminants in the soil environment due to their widespread occurrence and potential threat to soil health. However, their impacts on soil biogeochemical processes remain unclear. Here, we investigated the effects of TWP at various doses and their leachate on soil respiration and denitrification using a robotized continuous-flow incubation system in upland soil. Fourier transform ion cyclotron resonance mass spectrometry and high-throughput sequencing were employed to elucidate the mechanisms underpinning the TWP effects. We show that TWP increased soil CO2, N2, and N2O emissions, which were attributed to the changes in content and composition of soil dissolved organic matter (DOM) induced by TWP and their leachate. Specifically, the labile DOM components (H/C ≥ 1.5 and transformation >10), which were crucial in shaping the denitrifying community, were significantly enriched by TWP exposure. Furthermore, the abundances of denitrification genes (nirK/S and nosZ-I) and the specific denitrifying genera Pseudomonas were increased following TWP exposure. Our findings provide new insights into impacts of TWP on carbon and nitrogen cycling in soil, highlighting that TWP exposure may exacerbate greenhouse gas emissions and fertilizer N loss, posing adverse effects on soil fertility in peri-urban areas and climate change mitigation.

Tire and road wear particles in infiltration pond sediments: Occurrence, spatial distribution, size fractionation and correlation with metals

Stormwater systems, such as infiltration ponds or basins, play a critical role in managing runoff water and reducing particulate pollution loads in downstream environments through decantation. Road runoff carries several pollutants, including trace metals and tire and road wear particles (TRWP). To improve our understanding of infiltration ponds as regards TRWP and their capacity to reduce TRWP loads, we have studied the occurrence, spatial distribution and size distribution of TRWP, as well as their relationship with metals, in considering the input of metals as tire additives, in the sediments of an infiltration pond located along the Nantes urban ring road (Western France), which happens to be a high-traffic roadway site. The sediment was analyzed using pyrolysis coupled with gas chromatography-mass spectrometry to determine the polymeric content of tires, specifically in quantifying the styrene-butadiene rubber (SBR) and butadiene rubber (BR) pyrolytic markers. By applying an SBR + BR-to-TRWP conversion factor, the results showed significant TRWP contamination, up to 65 mg/g, with a spatial enrichment from the entrance to the overflow section of the pond. Size fractionation revealed a bimodal distribution, indicating two distinct types of TRWP. The first type is characterized by small diameters (63-160 μm), suggesting the presence of TRWP less integrated with mineral and organic particles. The second type, characterized by larger diameters (200-500 μm), suggests a more pronounced integration with these same mineral and organic particles. A significant positive correlation between TRWP and metals (As, Cd, Cr, Cu, Li, Mo, Ni, Sb, V, Zn) was found (r > 0.739, p < 0.05). This correlation implies that TRWP and/or their associated phases may act as an indicator of metal contamination in the pond sediments. Lastly, a mass balance between TRWP inputs and the amount retained in the sediments underscores the role of infiltration ponds as "sinks" for TRWP.

Tracking the biogeochemical behavior of tire wear particles in the environment - A review

The environmental fate and risks associated with tire wear particles (TWPs) are closely linked to their biogeochemical behaviors. However, reviews that focus on TWPs from this perspective remain scarce, hindering our understanding of their environmental fate and cascading effects on ecosystems. In this review, we summarize the existing knowledge on TWPs by addressing five key areas: (i) the generation and size-dependent distribution of TWPs; (ii) the release and transformation of TWP-leachates; (iii) methodologies for the quantification of TWPs; (iv) the toxicity of TWPs; and (v) interactions of TWPs with other environmental processes. It has been established that the size distribution of TWPs significantly influences their transport and occurrence in different matrices, leading to the release and transformation of specific TWP-chemicals that can be toxic to organisms. By highlighting the challenges and knowledge gaps in this field, we propose critical issues that need to be addressed to enhance the risk assessment of TWPs. This review aims to provide a comprehensive framework for evaluating the environmental behavior of TWPs.

Impact of Pristine and Aged Tire Wear Particles on Ipomoea aquatica and Rhizospheric Microbial Communities: Insights from a Long-Term Exposure Study

Tire wear particles (TWPs), generated from tire abrasion, contribute significantly to environmental contamination. The toxicity of TWPs to organisms has raised significant concerns, yet their effects on terrestrial plants remain unclear. Here, we investigated the long-term impact of pristine and naturally aged TWPs on water spinach (Ipomoea aquatica) and its rhizospheric soil. The results indicated that natural aging reduced the toxicity of TWPs, as evidenced by decreased levels of polycyclic aromatic hydrocarbons (PAHs) in soil and TWPs themselves. Consequently, aged TWPs were found to enhance the plant growth and chlorophyll content, whereas pristine TWPs increased the plant stress. Furthermore, aged TWPs improved soil organic matter (SOM) and total organic carbon (TOC), thereby boosting the microbial enzymes involved in nitrogen cycling. Metabolomic analysis revealed that aged TWPs upregulated key pathways related to carbon and nitrogen metabolism, enhancing plant growth and stress responses. Additionally, rhizosphere bacterial diversity was higher under aged TWPs, favoring nutrient-cycling taxa such as Acidobacteriota and Nitrospirota. Pristine TWPs may lead to overproliferation of certain dominant species, thereby reducing microbial diversity in soil, which could ultimately compromise the soil health. These findings contribute to a deeper understanding of the mechanisms underlying TWP toxicity in plants and highlight the necessity for further research on the impact of aged TWPs across various plant species over different exposure durations for comprehensive risk assessment.

Effect of UV exposure and natural aging on the in vitro PAHs bioaccessibility associated with tire wear particles in soil

Tire wear particles (TWP), as an emerging type of microplastics, are a significant source of contaminants in roadside soils due to their high concentration of pollutants, including polycyclic aromatic hydrocarbons (PAHs). This study explored the impact of ultraviolet (UV) exposure and natural aging on the in vitro bioaccessibility of PAHs associated with TWP in soil on a China-wide scale. Our findings suggested that UV exposure amplified the negative charge of TWP by 75 % and increased the hydrophobic groups on the particle surface. The bioaccessibility of 3- and 4-ring PAHs in TWP was significantly (p < 0.05) heightened by UV exposure. After 20 types of soils containing 2 % UV-exposed TWP underwent natural aging, the bioaccessibility of PAHs saw a significant decrease (p < 0.05) to 16-48 %, compared to 28-96 % in the unaged group. Soil pH and electrical conductivity (EC) were the two primary soil properties positively influencing the reduction of in vitro PAHs concentration and PAHs bioaccessibility. According to the prediction results, soils in southern China presented the highest potential region for the release of bioaccessible PAHs from TWP, highlighting the regional specificity of environmental impact. Our study provides valuable insights into the biological impact of PAHs associated with TWP on a regional scale, and offers scientific evidence for targeted soil risk management strategies.

Composition and concentrations of microplastics including tyre wear particles in stormwater retention pond sediments

Stormwater is recognised as a vector for microplastics (MPs), including tyre wear particles (TWPs) from land-based sources to receiving waterbodies. Before reaching the waterbodies, the stormwater may be treated. In this study, sediments from six treatment facilities (five retention ponds and a subsurface sedimentation tank) were analysed to understand MP occurrence, concentrations, sizes, polymer types and distribution between inlet and outlet. The concentrations of MPs showed large variations between and within different facilities with MP concentrations of 1,440-72,209 items/kg (analysed by μFTIR) corresponding to 120-2,950 μg/kg and TWP concentrations from

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Key Words

• FTIR imaging
• MP
• TWP
• pyrolysis–GC–MS
• stormwater management
• urban runoff

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MESH Headings

• Microplastics/analysis
• Geologic Sediments/chemistry
• Water Pollutants, Chemical/analysis
• Ponds
• Environmental Monitoring
• Rain/chemistry
• Particle Size

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Grants

• 2016-05176 VINNOVA
• 2022-03092 VINNOVA
• R092 Interreg
• Svenskt Vatten

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Affiliation(s)

Lisa Öborn Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden; Environment and Health Administration, City of Stockholm, Fleminggatan 4, Box 8136, Stockholm SE-104 20, Sweden
Heléne Österlund Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden E-mail:
Claudia Lorenz Division of Civil and Environmental Engineering, Department of the Built Environment, Aalborg University, Thomas Manns Vej 23 Aalborg Øst, 9220 Denmark; Department of Science and Environment, Roskilde University, Universitetsvej 1, Roskilde 4000, Denmark
Alvise Vianello Division of Civil and Environmental Engineering, Department of the Built Environment, Aalborg University, Thomas Manns Vej 23 Aalborg Øst, 9220 Denmark
Jeanette Lykkemark Division of Civil and Environmental Engineering, Department of the Built Environment, Aalborg University, Thomas Manns Vej 23 Aalborg Øst, 9220 Denmark
Jes Vollertsen Division of Civil and Environmental Engineering, Department of the Built Environment, Aalborg University, Thomas Manns Vej 23 Aalborg Øst, 9220 Denmark
Maria Viklander Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden

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Responses of colonization and development of periphytic biofilms to three typical tire wear particles with or without incubation-aging in migrating aqueous phases

Understanding the behavior of tire wear particles (TWPs) and their impact on aquatic environments after aging is essential. This study explored the characteristics of TWPs generated using different methods (rolling friction, sliding friction, and cryogenic milling) and their transformation after exposure to environmental conditions mimicking runoff and sewage, focusing on their effects on river water and periphytic biofilms. Laboratory experiments indicate that at low exposure levels (0.1 mg/L), TWPs promoted biofilm growth, likely due to zinc release acting as a nutrient and the aggregation of particles serving as biofilm scaffolds. However, at higher concentrations (100 mg/L), TWPs inhibited biofilm development. This inhibition is linked to toxic byproducts like N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone and environmentally persistent free radicals, which reduce biofilm biomass, alter algal diversity, and decrease the production of essential biofilm components such as proteins and polysaccharides, consistent with the inhibitory behavior of TWPs on bis-(3'-5')-cyclic diguanosine monophosphate and quorum sensing signals, including acyl-homoserine lactone and autoinducer-2. Aging processes, particularly after simulated sewage treatment, further affect ecological impacts of TWPs, reducing the benefits observed at low concentrations and intensifying the negative effects at high concentrations. Contribution of here lies in systematically revealing the impact of TWPs on the development of aquatic biofilms, emphasizing the logical relationship between their aging characteristics, environmental behavior, and ecological risks. It assesses not only the release effects of typical additives and conventional size effects but also highlights the emerging photochemical toxicity (persistent free radicals), thus providing valuable insights into the aquatic ecological risk assessment of TWPs.

Assessment of fine and coarse tyre wear particles along a highway stormwater system and in receiving waters: Occurrence and transport

Tyre wear has been identified as a major road-related pollutant source, with road runoff transporting tyre wear particles (TWP) to adjacent soil, watercourses, or further through stormwater systems. The aim of this study was to investigate the occurrence and transport of TWP along a stormwater system. Water and sediment have been sampled at selected points (road runoff, gully pots, wells, outlet to a ditch, and stream) through a stormwater system situated along a highway in Sweden during November and December 2022, and March 2023. As there is limited data on the size distribution of TWP in different environmental media, especially in the size fraction <20 μm, the samples were fractioned into a fine (1.6-20 μm) and a coarse (1.6-500 μm) size fraction. The samples were analysed using a combination of marker compounds (benzene, α-methylstyrene, ethylstyrene, and butadiene trimer) for styrene-butadiene rubbers with PYR-GC/MS from which TWP concentration was calculated. Suspended solids were analysed in the water samples, and organic content was analysed in the sediment samples. TWP was found at nearly all locations, with concentrations up to 17 mg/L in the water samples and up to 40 mg/g in the sediment samples. In the sediment samples, TWP in the size fraction 1.6-20 μm represented a significant proportion (20-60%). Correlations were found between TWP concentration and suspended solids in the water samples (r = 0.87) and organic content in the sediment samples (r = 0.72). The results presented in this study demonstrate that TWP can be transported to the surrounding environment through road runoff, with limited retention in the studied stormwater system.

Effects of tire wear particles on the water retention of soils with different textures in the full moisture range

Tire wear particles (TWPs) are significant contributors to microplastic pollution in the environment, yet there is limited scientific information concerning their impact on soil hydraulic properties. This study aimed to investigate the impact of TWPs at different concentrations (1, 4, 8, and 16% of the air-dried mass of packed soil samples, w/w) on the water retention curves (WRC) of southern California soils with five different textures (clay, clay loam, silt loam, sandy loam, and loamy sand). The concentrations of 8% and 16% were selected to represent extreme pollution scenarios that might occur near highway corridors. High-resolution water retention data, spanning from saturation to oven dryness, were generated using HYPROP™ and WP4C dew point meter instruments. We also developed WRC scaling equations based on the quantity of TWPs. The bulk density of the samples decreased as the TWP concentration in soils increased. The inclusion of very high concentrations of TWPs (8% and 16% w/w) led to a significant reduction in soil moisture content in the intermediate and dry ranges across various soil textures. However, at the same moisture range, adding 1% TWPs had a minimal impact on soil moisture reduction, while the influence of the 4% TWPs concentration treatment was noticeable only in loamy sand and partially in clay loam soils. Additionally, the overall plant available water decreased with increasing TWP concentrations, except for the clay soil. The texture-specific scaling models exhibited promising performance, with RMSE values ranging from 0.0061 to 0.0120 cm3 cm-3. When bulk density was included as an additional input predictor to construct a single scaling model for all textures, the RMSE increased. Nevertheless, it still indicated a good fit ranging from 0.007 to 0.024 cm3 cm-3, highlighting the suitability of simple scaling for identifying WRC in TWPs-polluted soils, particularly for practical purposes. The findings of this study can contribute to a better understanding and quantification of the impact of TWPs on soil hydrology.

Mixture toxicity of 6PPD-quinone and polystyrene nanoplastics in zebrafish

Plastic pollution, including micro- and nanoplastics, is a growing concern. Tyre-wear particles (TWPs) are the second largest source of microplastics in the ocean following abrasion of synthetic fibres. In addition to the particles themselves, TWPs contain many harmful chemicals, including 6PPD. This chemical reacts with atmospheric ozone and forms the toxic compound 6PPD-quinone (6PPDq), which poses a danger to aquatic life. There is a knowledge gap in understanding risks associated with the combined toxicity of nanoplastics (NPs) and 6PPDq. The present study aimed to investigate the toxicity of NPs and 6PPDq on adult zebrafish using phenotypic (behaviour, histology) and transcriptomic endpoints. Zebrafish were exposed to four treatments: control (contaminant-free), 50 μg/L 6PPDq, 3 mg/L polystyrene (PS)-NPs, and a combination of 50 μg/L 6PPDq and 3 mg/L PS-NPs. We did not observe locomotory dysregulation in zebrafish exposed to NPs. However, we found significant hyperlocomotion in zebrafish exposed to 6PPDq and this effect was even more substantial after co-exposure with PS-NPs. This study explores the molecular mechanisms behind these effects, identifying genes associated with neurotransmitters and fatty acid metabolism that were dysregulated by the co-exposure. Transcriptomic analysis further showed that both 6PPDq and PS-NPs impacted cellular processes associated with sterol biosynthesis, cholesterol metabolism, and muscle tissue development. The effects on these mechanisms were stronger in co-exposed zebrafish, indicating a heightened risk to cellular integrity and mitochondrial dysfunction. These results highlight the significance of mixture toxicity when studying the effects of NPs and associated chemicals like 6PPDq.

Types and concentrations of tire wear particles (TWPs) in road dust generated in slow lanes

Drivers commonly navigate their vehicles at moderate speeds in proximity to traffic lights. In this study, road dust samples were collected in the vicinity of traffic lights, as well as at a taxi stand (TS) situated between traffic lights, with considerations given to both forward direction (FD) and backward direction (BD). The characterization of tire wear particles (TWPs) in the road dust was meticulously conducted based on particle size. Notably, tire-road wear particles (TRWPs) were conspicuously absent in samples surpassing 500 μm. Furthermore, TRWPs comprised less than 1% of identified particles in the road dust samples of 212-500 μm, with their origin traceable to heavy vehicles rather than passenger cars. The abundance of TRWPs from heavy vehicles exhibited marked variations, with heightened prevalence in the TS and BD samples as opposed to the FD sample. For the samples smaller than 212 μm, the composition of natural rubber (NR) in TWPs demonstrated a diminishing trend with escalating particle size. Conversely, the composition of styrene-butadiene rubber (SBR) exhibited an upward trajectory independent of the sampling site. The NR composition ratio in TWPs followed the order: TS (17-55%) > FD (17-47%) > BD (13-36%), while the SBR composition ratio exhibited the sequence: BD (62-86%) > FD (48-79%) > TS (24-70%). The TWP concentrations in road dust obtained from the TS (0.35-0.82%) were discernibly lower than those in the FD (0.54-1.77%) and BD (0.61-1.29%) samples. Specifically, the average TWP concentrations in road dust samples, falling within the size range of 20-212 μm, were 0.45%, 1.06%, and 0.91% for the TS, FD, and BD samples, respectively. These concentrations were lower than the corresponding values observed in samples collected from a bus stop.

Photoaged Tire Wear Particles Leading to the Oxidative Damage on Earthworms (Eisenia fetida) by Disrupting the Antioxidant Defense System: The Definitive Role of Environmental Free Radicals

Tire wear particles (TWPs) have caused increasing concerns due to their detrimental effects on the soil ecosystem. However, the role of weathering in altering the toxicity of TWP to soil organisms is poorly understood. In this study, the toxicity of original and photoaged TWP was compared using earthworms (Eisenia fetida) as soil model organisms. The obtained results indicated that photoaging of TWP resulted in an increase of environmentally persistent free radicals (EPFRs) from 3.69 × 1017 to 5.20 × 1017 spin/g. Meanwhile, photoaged TWP induced the changes of toxic endpoint in E. fetide, i.e., the increase of the weight loss and death ratio from 0.0425 to 0.0756 g/worm and 23.3 to 50% compared to original TWP under a 10% concentration, respectively. Analyses of transcriptomics, antioxidant enzyme activity, and histopathology demonstrated that the enhanced toxicity was mainly due to oxidative damage, which was induced by disruption in the antioxidant defense system. Free-radical quenching and correlation analysis further suggested that the excessive production of ex vivo reactive oxygen species, induced by EPFRs, led to the exhaustion of the antioxidant defense system. Overall, this work provides new insights into the potential hazard of the weathered TWP in a soil environment and has significant implications for the recycling and proper disposal of spent tire particles.

Abundance and distribution of tire and road wear particles in the Seine River, France

Tire and road wear particles (TRWP) are formed at the frictional interface between tires and the road surface. Tire tread and road pavement materials are denser than water but can be washed from the road surface into receiving water bodies, ultimately depositing into sediment, soil, or other media depending on the receiving environment. However, the paucity of mass-based measurements has limited the knowledge on the nature and extent of environmental concentrations necessary for environmental risk assessment of TRWP. Surface water and sediment samples were collected from the Seine River, France to characterize TRWP concentration. Sample locations were established upstream, within, and downstream of a major metropolitan area (Paris); downstream of smaller urban areas; adjacent to undeveloped land; and near the confluence of the estuary. Surface water and sediment were collected from the left and right banks at each of the eight locations, including two duplicates, for a total of 18 samples. Additionally, three sediment traps were deployed near the mouth of the river to quantify the flux of TRWP to sediment. Retained solids and sediment samples were analyzed using a modified pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) method that minimized the matrix interferences in the samples thus improving the current ISO Technical Specification ISO/TS 21396 : 2017 for TRWP mass concentration by Py-GC/MS. TRWP concentration was alternatively estimated by separating the sediment into the <1.9 g cm-3 fraction and analyzing for tread-derived zinc content. TRWP concentrations estimated by zinc method were significantly higher than results from the modified Py-GC/MS method. TRWP and total zinc concentrations show a decreasing trend from available historical data.