Analysis of Tyre Tread for Metal Tracers with Applications in Environmental Monitoring

Abstract

The purpose of this study was to identify a characteristic elemental tyre fingerprint that can be utilised in atmospheric source apportionment calculations. Currently zinc is widely used as a single element tracer to quantify tyre wear, however several authors have highlighted issues with this approach. To overcome this, tyre rubber tread was digested and has been analysed for 25 elements by ICP-MS to generate a multielement profile. Additionally, to estimate the percentage of the tyre made up of inert fillers, thermogravimetric analysis was performed on a subset. Comparisons were made between passenger car and heavy goods vehicle tyre composition, and a subset of tyres had both tread and sidewall sampled for further comparison. Finds showed 19 of the 25 elements were detected in the analysis. The mean mass fraction of zinc detected was 11.17 g/kg, consistent with previous estimates of 1% of the tyre mass. Aluminium, iron, and magnesium were found to be the next most abundant elements, and barium, magnesium and tin were all detected at higher concentrations than have been reported previously. The analysis found significant differences in elemental composition of goods vehicle and passenger car tyres, which could potentially allow for separate source profiles for each type. Only one source profile for tyre wear exists in both the US and EU air pollution species profile databases, highlighting the need for more recent data with better coverage of tyre makes and models. This study provides data on new tyres which are currently operating on-road in Europe and is therefore relevant for ongoing atmospheric studies assessing the levels of tyre wear particles in urban areas.

Traceable determination of metal composition of tyres using tandem ICP-MS and benchmarking of emissions inventories

“…Although studies previously have investigated different metals, the mass fractions measured for Ni and Pb were comparable with other reports. 7,8,14 Results for Fe, Ba and Cu were lower than those for other tyres previously reported, while that of Al was higher. 7,8,14 The reason for lower Fe values being reported here than in previous studies could be due to the removal of the ArO interference, which was not carried out in the other studies referred to in this paper.…”

“…7,8,14 Results for Fe, Ba and Cu were lower than those for other tyres previously reported, while that of Al was higher. 7,8,14 The reason for lower Fe values being reported here than in previous studies could be due to the removal of the ArO interference, which was not carried out in the other studies referred to in this paper. The mass fraction of Ba was expected to be low due to its presence in brake wear as opposed to tyre wear.…”

“…The analytes with the highest responses in the qualitative analysis were selected for further quantitative measurement; namely Zn, Al, Fe, Ti, Pb and Mg. Zinc is widely known to be added (as ZnO) as a vulcanisation accelerator, while other metals are used as polymerisation catalysts or are present as contaminants of crude oil. 1,6,7,[10][11][12][13] Although showing a high response in the qualitative analysis, Zr and La were not selected for further analysis as they were not expected to be present in tyres and were likely to be a result of polyatomic interferences rather than indicate the presence of the metals themselves. Ni and Cu were selected due to literature examples of their presence in tyres, 8,14 and Ba as a primary component in brake wear.…”

“…4 Tyres are made primarily from natural and synthetic rubber hydrocarbons; ller such as soot, carbon black, silica and chalk; soener consisting of oil and resin; textile and metal reinforcement; vulcanization agents and other additives including preservatives, anti-oxidants, desiccants, and plasticisers. 2,[5][6][7] However, this composition can vary signicantly between manufacturers and performance specications. 2 There have been previous studies to address lack of data on elemental composition of tyres.…”

“…2 There have been previous studies to address lack of data on elemental composition of tyres. 2,7,8 Jeong 8 presents data on toxic metals and Cu, Zn, and Pb isotopic compositions. Acid digestion with HF and multi-collector ICP-MS analysis was used to determine that while Zn was the highest metal concentration overall, Ni, Zn, Sn, and Sb were higher in domestic tyres (South Korea) than imported tyres, and there were large differences between tyre products and manufacturers.…”