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Traffic Rather Than Land Use Influences Tire-Derived Organic Pollutants in Urban Soils

Year: 2026
Type: preprint
Abstract: Tire-derived organic pollutants (TDOPs), particularly antioxidant N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and its transformation product N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine quinone (6PPD-quinone), are increasingly recognized as emerging urban contaminants. However, their distribution and controlling factors in urban soils beyond the immediate roadside environment remain poorly characterized. In this study, 19 TDOPs, including 6PPD and 6PPD-quinone, were quantified in 28 urban soil samples representing four land-use types in the highly urbanized Metro Detroit, Michigan, United States, where heavy traffic creates a strong potential for tire-derived contamination. TDOPs were widely detected in all soil samples, and 16 out of 19 compounds had a detection frequency ≥75%. Very low 6PPD/6PPD-quinone ratios, together with the relative enrichment of N,N'-diphenyl-p-phenylenediamine (DPPD) over 6PPD, suggest that substantial transformation of 6PPD had occurred in the investigated urban soils. Statistical analyses showed no significant differences among land-use types. In contrast, traffic-derived exposure metrics showed significant associations with a subset of TDOPs, with 6PPD exhibiting the strongest correlation. The Pearson correlation coefficient between log10-transformed 6PPD concentrations and log10-transformed traffic-derived exposure metrics reached a maximum of 0.730 at a decay length of 400 m ( p < 0.0001). These results show that soil contamination by TDOPs extends beyond the immediate roadside environment and suggest that traffic intensity (source strength), proximity, and environmental fate and transport processes jointly govern TDOP accumulation in urban soils.
Source: ChemRxiv
DOI: 10.26434/chemrxiv.15004348/v1
Language: English
Open Access status: green
OpenAlex ID: W7163639890
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