Benzotriazoles, Benzothiazoles and Trace Elements in an Urban Road Setting in Trondheim, Norway: Re-Visiting the Chemical Markers of Traffic Pollution

Abstract

Road traffic emissions are known to contribute heavily to the pollution in urban environments. The aim of this study was to establish specific traffic pollution markers in an urban road setting based on the occurrence profiles of benzotriazoles, benzothiazoles and trace elements in road dust and relevant matrices, including airborne particulate matter and core asphalt. Benzotriazoles and benzothiazoles are high-production volume chemicals that are used as complexing and anticorrosive agents for metals, act as vulcanizing accelerators for rubber materials, and possess anti-freezing/anti-icing properties. In this study, six benzothiazoles (benzothiazole, 2‑morpholin‑4‑yl‑benzothiazole, 2‑hydroxy‑benzothiazole, 2‑thio‑benzothiazole, 2‑methylthio‑benzothiazole, and 2‑amino‑benzothiazole), seven benzotriazoles (1H‑benzotriazole, 1‑hydroxy‑benzotriazole, 5‑chloro‑1H‑benzotriazole, tolyltriazole, xylyltriazole, benzotriazole‑5‑carboxyl acid, and 5‑amino‑1H‑benzotriazole), and 66 trace elements were determined in road dust samples from a sub-arctic urban road setting in Norway, and seasonal occurrence profiles were assessed between the studded and the non-studded tire season. The road dust was collected as suspended particulate matter in an aqueous phase with the introduced dust sampler in Scandinavia, the Wet Dust Sampler. The concentrations of the sum of seven benzotriazoles (Σ(7)BTRs) and six benzothiazoles (Σ(6)BTHs) in road dust ranged from 191 to 3054 ng/L and 93.4 to 1903 ng/L, respectively. To the best of our knowledge, 1H‑benzotriazole and tolyltriazole are reported for the first time as suitable markers of metal corrosion in vehicles. From the benzothiazole class, 2‑thio‑benzothiazole was found to be a suitable marker of tire rubber particles, while its methylated derivative, 2‑methylthio‑benzothiazole, was found to be a marker of chemical leaching. In addition, different types of new unused tires (summer, studded, and non-studded) were analyzed to assess their benzothiazoles and benzotriazoles content. Based on the concentrations found for benzotriazoles and benzothiazoles in airborne particulate matter, human exposure doses were calculated, and the estimated daily intake doses were found on the order of picograms per day.