Occurrence of traffic related trace elements and organic micropollutants in tunnel wash water

Abstract

Tunnel wash water (TWW) is highly polluted water produced during road tunnel maintenance, with previous literature reporting the presence of trace elements and polycyclic aromatic hydrocarbons (PAHs). However, it was hypothesized that other organic pollutants are present, and more knowledge is needed to prevent environmental harm. This study reveals for the first time the presence of four short- and 17 long-chained per- and polyfluoroalkyl substances (PFASs), three benzothiazoles, six benzotriazoles, four bisphenols, and four benzophenones in TWW from a Norwegian road tunnel over a period of two years. Concentrations of PAHs, PFASs, BTHs, and BTRs were higher than previously reported in e.g., road runoff and municipal wastewater. Trace elements and PAHs were largely particulate matter associated, while PFASs, benzothiazoles, benzotriazoles, bisphenols, and benzophenones were predominantly dissolved. 29 of the determined contaminants were classified as persistent, mobile, and toxic (PMT) and are of special concern. It was recommended that regulations for TWW quality should be expanded to include PMT contaminants (such as PFPeA, PFBS, BTR, and 4-OH-BzP) and markers of pollution (like 2-M-BTH, 2-OH-BTH, and 2-S-BTH from tire wear particles). These findings highlight the need to treat TWW before discharge into the environment, addressing both, particulate matter associated and dissolved contaminants. This manuscript should be considered for publication since it is of great environmental importance. It documents and evaluates the presence of numerous hazardous substances: toxic trace elements, PAHs, PFASs, benzothiazoles, benzotriazoles, bisphenols, and benzophenones in TWW. Many contaminants are investigated for the first time in TWW, and have recently been categorised as being persistent, mobile, and toxic (PMT) substances. It is shown that these substances will end up in the environment, where they can cause significant harm, thus, suggestions are made about possible discharge regulation and treatment. The study has been conducted at a tunnel in operation, under realistic conditions.