Rubber-derived Chemicals in Urban Sewer Networks and Receiving Waters: Fingerprints, Driving Factors and Ecological Impacts.

Rubber-derived chemicals (RDCs), which include rubber additives (RAs) and their transformation products (TPs), can be released into aquatic environments when rubber products, such as vehicle tires, are in use or discarded. However, RDCs and associated ecological risks have not been thoroughly investigated inside urban sewer networks and their receiving water bodies. To address these issues, we investigated the RDCs in Hong Kong's municipal sewer networks, including sewage and stormwater, as well as their receiving waters, such as rivers and coastal water. Among 45 target RDCs, the vulcanizing agents and corrosion inhibitors were found to be predominant in the water samples, accounting for 26-66 % and 29-72 % of total concentrations of 45 RDCs (∑45RDC), respectively, while antioxidants and their TPs presented in smaller quantities, accounting for 0.21-26 % and 0-15 % of ∑45RDC, respectively. Ten RAs from five classes were additionally identified by suspect screening. An estimated mass load of ∑45RDC amounting to 1690 kg/month is discharged into the coastal marine environment of Hong Kong, with sewage effluent being the primary source. Population density and vehicle-related factors (e.g., traffic load) were the major drivers shaping the spatial distribution of RDCs in surface water. Based on the ecological risk assessment outcomes, 16 out of 45 RDCs exhibited medium to high risks, and lists of candidate contaminants for various water bodies were proposed to support future risk management in water quality. These findings suggest that RDCs in stormwater and rivers should be carefully monitored, and management strategies should be developed to mitigate their risks.