Rationale Tunnel wash water (TWW) accumulates tire-road wear particles (TRWPs), tire-derived chemicals (TDCs), and metals at high concentrations, posing risks to aquatic ecosystems if untreated. Understanding pollutant retention and transformation during treatment is essential for effective mitigation. Methodology We investigated TWW from the Vålereng tunnel (Oslo, Norway) using a multi-analytical approach. TRWPs were quantified by pyrolysis-GC/MS with a marker mix (M4), a single marker (4-VCH), and automated SEM-EDX single particle analysis with machine-learning classification (ASPA MC2™). Metals were analyzed by ICP-MS and TDCs by UPLC-MS/MS. Samples were collected before, during and after sedimentation treatment over 21 days. Results Zinc was the most abundant metal (274–2300 µg/L), reduced by up to 93% post-treatment. TRWP concentrations ranged from 15–160 mg/L (M4), 13–122 mg/L (4-VCH), and 13–240 mg/L (ASPA MC2™), with treatment efficiencies of 95–99.7%. Despite reductions, fine particles (20 µm) dominated both untreated and treated water (up to 85%). For TDCs, 6PPD showed 85% reduction, while 6PPD-Q (-26%) and DPG (-3.7%) exhibited negative retention, likely due to leaching and transformation. OHBT increased by up to 167% during sedimentation. Discussion Sedimentation effectively removed particles and metals but was insufficient for several dissolved TDCs, releasing them at ecotoxicologically relevant concentrations (e.g., 6PPD-Q exceeded EPA freshwater limits). This first cross-validation of three TRWP quantification methods highlights the need for advanced treatment technologies and regulatory thresholds for tire-derived pollutants.
Rødland et al. (Thu,) studied this question.