Sources and properties of non-exhaust particulate matter from road traffic: a review.

Tire-tread material has a zinc (Zn) content of about 1 wt %. The quantity of tread material lost to road surfaces by abrasion has not been well characterized. Two approaches were used to assess the magnitude of this nonpoint source of Zn in the U.S. for the period 1936−1999. In the first approach, tread-wear rates from the automotive engineering literature were used in conjunction with vehicle distance-driven data from the U.S. Department of Transportation to determine Zn releases. A second approach calculated this source term from the volume of tread lost during lifetime tire wear. These analyses showed that the quantity of Zn released by tire wear in the mid-1990s was of the same magnitude as that released from waste incineration. For 1999, the quantity of Zn released by tire wear in the U.S. is estimated to be 10 000−11 000 metric tons. A specific case study focused on Zn sources and sinks in an urban−suburban watershed (Lake Anne) in the Washington, DC, metropolitan area for a time period of the late ...

Tire-wear particles as a source of zinc to the environment

Sources of heavy metals in urban wastewater in Stockholm

Tire wear particles in the aquatic environment - A review on generation, analysis, occurrence, fate and effects.

In recent years, marine, freshwater and terrestrial pollution with microplastics has been discussed extensively, whereas atmospheric microplastic transport has been largely overlooked. Here, we present global simulations of atmospheric transport of microplastic particles produced by road traffic (TWPs – tire wear particles and BWPs – brake wear particles), a major source that can be quantified relatively well. We find a high transport efficiencies of these particles to remote regions. About 34% of the emitted coarse TWPs and 30% of the emitted coarse BWPs (100 kt yr−1 and 40 kt yr−1 respectively) were deposited in the World Ocean. These amounts are of similar magnitude as the total estimated direct and riverine transport of TWPs and fibres to the ocean (64 kt yr−1). We suggest that the Arctic may be a particularly sensitive receptor region, where the light-absorbing properties of TWPs and BWPs may also cause accelerated warming and melting of the cryosphere. Plastic pollution is a critical concern across diverse ecosystems, yet most research has focused on terrestrial and aquatic transport, neglecting other mechanisms. Here the authors show that atmospheric transport is a major pathway for road plastic pollution over remote regions.

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Atmospheric transport is a major pathway of microplastics to remote regions

This paper is directed to air pollution scientists interested in special mobile emission sources. The purpose was to determine the contribution which automobile tires make to air pollution. The gaseous hydrocarbon and sulfur compounds emitted in laboratory tests were identified. Although these hydrocarbons can participate in smog reactions, their mass emission rate is less than 0.1 % of the current exhaust hydrocarbon emission rate. Hydrocarbons from tires are not measurable near a freeway. The particulate emitted from tires ranges in size from 0.01 μm to more than 30 μm, with the larger particles dominating the total mass. Measurements along a California freeway showed that most of the tire debris had settled within 5 m of the pavement edge. Airborne rubber concentrations were less than 0.5 μg/m3, or less than 5% of the total tire wear. These field measurements confirm the indoor emission pattern and verify that tire wear products are not a significant air pollution problem.

Gas and particle emissions from automobile tires in laboratory and field studies

Four sample types (tire-wear particulate and tread rubber each in roadside soil and in glass beads) were analyzed periodically for total rubber content by thermogravimetric (TGA), pyrolysis-gas chromatography (GC), and extraction-pyrolysis-GC analyses. Results of the extraction analysis (the most reliable method) show that after 16 months, 52% of the polymer in tread-wear particulate was degraded in soil and only 36% in glass beads (possibly due to lack of soil microorganisms to degrade sulfur linkages in the vulcanized portion of the polymer). Fresh tread particles of the same size showed no degradation. Pyrolysis-GC results, although showing wide scatter, showed that the unsaturated bonds of polybutadiene undergo oxidative degradation more rapidly than the aromatic bonds of styrene units. These results strongly suggest that one important mode of degradation of tread-wear particles is atmospheric oxidation. TGA results show that biodegradation did not reduce the total carbon content of the wear particles in the 16 months, although more than half of the extender oil was oxidized sufficiently to increase its vaporization temperature to the polymer temperature range. Biooxidation may have detoxified some of the polynuclear aromatic hydrocarbon portion of the oil. The rate of environmental degradation was 0.15% per day, 22% of the total removal rate found in a California roadside study. Wind erosion and water run-off probably account for some removal.

Environmental Degradation of Tire-Wear Particles

Gas and Particle Emissions from Automobile Tires in Laboratory and Field Studies

A tire emission facility has been built in which several tire-wear modes can be simulated while the gaseous, airborne particulate, and sedimentary particulate emissions are collected. The facility was shown to produce tire temperatures and wear rates typical of operating tires. This approach to tire-emission research has many advantages over previous attempts to study tire emissions. The emission rate of gases and airborne particulate matter was nearly independent of wear rate and accounted for only 1–20% of the total emissions. The balance of the emissions were large particles which would be expected to settle on or very close to roadways. Chemical analysis of these large particles showed that approximately 30% of the SBR is unvulcanized, compared to only 1–2% in the tread. The total organic content of the particles was unchanged. This degradation of the rubber leads to enhanced oxygen absorption rates. However, the full significance of the increased rate of oxidation is not known.

S. H. Cadle

Papers

Gas and particle emissions from automobile tires in laboratory and field studies

Environmental Degradation of Tire-Wear Particles

Gas and Particle Emissions from Automobile Tires in Laboratory and Field Studies

Characterization of Tire Emissions Using an Indoor Test Facility