New insights into the occurrence of vehicle related compounds in one of Europe’s longest rivers

Vehicle Related Compounds (VRCs) are considered emerging contaminants arising from road traffic. These compounds consist of a complex mixture of chemicals related to additives used in various parts of the vehicle such as brakes, tires or different vehicle fluids. The objective of this study was to investigate the occurrence of VRCs in surface waters in one of the longest rivers in Europe (Tagus River, Spain). Samples (n=89) were collected during 2020-2022 from thirteen locations along the entire river in annual and seasonal campaigns and analyzed by liquid chromatography coupled to high-resolution mass spectrometry. A qualitative suspect workflow including an initial suspect list of 153 environmentally relevant VRCs was developed. Up to 26 compounds presented detection frequencies (DF) above 20% in the investigated river waters. Vulcanizers, cross-linkers, bittering agents or corrosion inhibitors stand out among the main classes of additives where hexa(methoxymethyl)melamine (HMMM) and derivatives, denatonium benzoate (DB), benzothiazole-2-sulfonic acid (BTSA) and 1-H-benzotriazole (BTR) were the most frequently detected compounds (DF>75%). Among the high intensity suspects, the vulcanizers triisopropanolamine (TIPA) and 1,3-diphenylguanidine (DPG) and the corrosion inhibitor 5-Methyl-1H-benzotriazole (Me-BTR) were also prominent. The detection of some tire-related markers and the fate of most of the identified VRCs highlighted a common anthropogenic origin, although variable sources for some of them are possible. This study illustrates the capabilities of suspect screening in assessing the presence of VRCs in river water and its potential as a monitoring tool to provide insights into the pollutant load influenced by parameters such as the urbanization degree. • 46 VRCs have been detected in the surface waters of one of Europe's longest rivers. • Traffic and urbanization are the main source of VRC compounds in the studied river. • Suspect analysis is a valid strategy to assess pollutant differences and loads. • Detecting additive transformation product shows the need for wide-scope analyses. • HMMM, 6PPD-Q and 6PPD-TP274 were identified for the first time in Spanish rivers.