Occurrence and distribution of UV absorbents in the surface water of the endangered St. Lawrence Estuary beluga’s habitat

Amina  Ben Chaaben, Mathieu Babin, Frank Wania, Hayley Hung, Magali Houde, Liisa Jantunen, Huixiang Xie, Zhe Lu

UV absorbents (UVAs) are contaminants of emerging environmental concern that are derived from sunscreens, personal care products, plastics, and many other products to protect skin from sunburn or prevent the materials from UV-induced color change or degradation. UVAs have been detected in the blubber and/or liver of beluga whales (Delphinapterus leucas) and their food web in St. Lawrence (SL) Estuary, demonstrating the presence of UVAs in the habitat of SL Estuary beluga and the potential input of these contaminants from the rivers draining into this system, such as the SL River and the Saguenay River. However, little is known about the concentrations and distributions of UVAs in waters of this system. In the present study, two groups of UVAs, UV filters (UVFs) and benzotriazole UV stabilizers (BZT-UVs), were analyzed in surface water samples collected in 2019-2020 from 45 coastal and 15 offshore sites of the SL Estuary, SL River, and the Saguenay River, to elucidate the spatial distributions of UVAs. Samples were filtered to separate the aqueous dissolved phase and suspended particulate matter (SPM) for analysis. Four BZT-UVs and two UVFs were frequently detected (>50%) in the dissolved phase. Compared to the SL Estuary, the river samples showed higher detection frequency and concentrations of four BZT-UVs and three UVFs in the dissolved phase. Preliminary results of the SPM samples showed the detection of nine BZT-UVs and six UVFs. UV328, a BZT-UV currently under evaluation by the Stockholm Convention, was detected more frequently in SPM (53% of samples, up to 1.9 μg/g) compared to the dissolved phase (17%, up to 4.2 ng/L). The high abundance of UVAs on SPM suggests that the ingestion of SPM could be an important exposure pathway to BZT-UVs and UVFs for aquatic organisms. This study provides a baseline for future monitoring of UVAs in the habitat of the SL Estuary beluga.