Tire Additives Dominate River Pollution Through Suspended Particles

Tire additives and their transformation products are increasingly recognized as contaminants of global concern, yet their behavior in large river systems has remained poorly characterized. A new study of China’s Qiantang River now provides one of the most detailed pictures to date, tracking 38 of these compounds across three environmental phases and four distinct seasons.

The research identified seventeen tire-derived compounds in the river, with N,N′-diphenylguanidine (DPG) and N,N′-di-o-tolylguanidine (77PD) emerging as the predominant congeners.

Spatial patterns revealed significant heterogeneity in concentrations. Higher levels were observed in downstream urbanized regions and during the wet season, a pattern the authors interpret as evidence that runoff drives inputs into the river.

Perhaps the most striking finding concerns where these chemicals reside within the river. Compounds associated with suspended particulate matter accounted for more than 54 percent of total concentrations, underscoring the role of particles as the primary vector transporting tire additives through the system.

The study examined partitioning across three phases: freely dissolved compounds, those associated with dissolved organic carbon, and those bound to suspended particulate matter. Partitioning coefficients for both organic carbon and dissolved organic carbon correlated strongly with hydrophobicity, measured as logKOW, meaning that more water-repellent compounds showed a stronger tendency to associate with organic matter rather than remain in the water column itself.

Seasonality also shaped this partitioning. Sorption to organic phases peaked in winter, a pattern consistent with exothermic partitioning processes, in which lower temperatures favor the transfer of compounds from water onto organic matter.

The ecological risk assessment identified one compound as a particular concern. Hexamethylolmelamine (HMMM) presented significant risks at approximately 80 percent of the sites examined. In contrast, 77PD, N-cyclohexyl-N′-phenyl-p-phenylenediamine (CPPD), and DPG demonstrated moderate risk levels across the river system.

The authors emphasize that seasonal hydrology and organic matter exert crucial influence on the fate of these tire-derived contaminants in the Qiantang River. Based on the risk profile, they highlight the necessity for prioritized monitoring of HMMM and compounds related to 77PD in urban watershed environments, where runoff-driven inputs and particle transport combine to shape exposure downstream.

Subject of Research: Spatial distribution, three-phase partitioning, and ecological risks of tire additive transformation products in the Qiantang River, China

Article Title: Spatial distribution, partitioning, and ecological risk assessment of tire additives and their transformation products in the Qiantang River of China

Article References: Hua, Z., Zhang, X.-L., Jiang, J.-M., Ye, C., Zhang, J., Liu, H., Mu, Y.-T., Lan, X.-S., Ouyang, J., Li, F., & Hong, W.-J. (2026). Spatial distribution, partitioning, and ecological risk assessment of tire additives and their transformation products in the Qiantang River of China. Environmental Geochemistry and Health, 48(16), Article 668. https://doi.org/10.1007/s10653-026-03566-1

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03566-1

Keywords: tire additives, transformation products, Qiantang River, suspended particulate matter, partitioning, ecological risk assessment, HMMM, DPG, 77PD, seasonal variation, urban runoff, water contamination