Measurement of tyre-related chemicals in roadside retention ponds using the Chemcatcher passive sampler: An ex-situ calibration and in-situ monitoring study

Tyre-related chemicals are emerging environmental pollutants. They can reach the aquatic environment via sustainable drainage systems (e.g., retention ponds). However, little is known about tyre chemicals in these engineered environments which themselves are important ecosystems. A key challenge of monitoring tyre chemicals is their changeable concentrations caused by road runoff. Therefore, it was proposed to establish a longer-term monitoring approach (e.g., ≥ 7 days) to complement low frequency grab sampling for improved fate and exposure assessments. A hydrophilic-lipophilic balance-Chemcatcher passive sampler configuration was assessed for uptake of 11 tyre-related chemicals including 1,3-diphenylguanidine, hexamethoxymethylmelamine (HMMM), and N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine-quinone (6PPD-quinone). Ex-situ 14-day uptake calibrations showed linear uptake (r² values ≥ 0.9) in pond water with sampling uptake rates (R_S) in the range 0.0073 – 0.054 L/d. Both water temperature and flow velocity had a significant effect (p-value < 0.05) on RS value for some chemicals. Subsequent in-situ monitoring revealed little reduction in tyre chemical concentrations through two retention pond systems. Nevertheless, 7-day and 14-day time weighted average concentrations were below the provisional predicted no effect concentration (PNEC) for most chemicals. However, all samples exceeded the current PNEC for HMMM (1.7 × 10⁻² µg/L) and by ≥ 20 times for some samples suggesting need for ‘upstream’ or within pond intervention. Non-targeted analysis tentatively identified a further 20 potential chemicals of interest in Chemcatcher extracts including vulcanisation accelerators, plasticisers and transformation products. Overall, the proposed Chemcatcher passive sampler can complement grab sampling to better monitor tyre-related chemicals in surface waters for their improved management.