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Nowadays, the industry is quite commonly using nanoparticles of titanium dioxide (nTiO₂) especially in sunscreens, due to its higher reflective index in comparison to micron size TiO₂. Its high demand causes its widespread environmental occurrence, thus damaging the environment. The aquatic ecosystems are the most vulnerable to contamination by nTiO₂. Like other engineered nanoparticles, nTiO₂ has demonstrated generation of reactive oxygen species (ROS) and reactive halogen species (RHS) in the aquatic environment under UV radiation. This study investigated the toxicity of nTiO₂ towards two aquatic indicator organisms, one from freshwater (Daphnia magna) and the other from seawater (Artemia sp.), under simulated solar radiation (SSR). Daphnia magna and Artemia sp. were co-exposed in 16 h SSR and 8 h darkness cycles to different concentrations of nTiO₂. The estimated EC50 at 48 h for D. magna was 3.16 mg nTiO₂/L, whereas for A. sp. no toxic effects were observed. When we exposed these two organisms simultaneously to 48 h of prolonged SSR using higher nTiO₂ concentrations, EC50 values of 7.60 mg/L and 5.59 mg/L nTiO₂ for D. magna and A. sp., respectively, were obtained. A complementary bioassay was carried out with A. sp., by exposing this organism to a mixture of nTiO₂ and organic UV filters (benzophenone 3 (oxybenzone, BP3), octocrylene (OC), and ethyl 4-aminobenzoate (EtPABA)), and then exposed to SSR. The results suggested that nTiO₂ could potentially have negative impacts on these organisms, also this work outlines the different characteristics and interactions that may contribute to the mechanisms of environmental (in salted and freshwater) phototoxicity of nTiO₂ and UV radiation, besides their interaction with organic compounds. Full article

In this paper, the ultraviolet/persulfate (UV/PDS) combined oxidation process was used to remove the ethyl 4-aminobenzoate (Et-PABA), one of the typical 4-aminobenzoic acid (PABA)-type UV filters. The effects of various factors on the removal of Et-PABA using the UV/PDS process were investigated, and the degradation mechanisms of Et-PABA were explored. The results showed that the UV/PDS process can effectively remove 98.7% of Et-PABA within 30 min under the conditions: UV intensity of 0.92 mW·cm⁻², an initial concentration of Et-PABA of 0.05 mM, and a PDS concentration of 2 mM. The removal rate of Et-PABA increased with the increase in PDS dosage within the experimental range, whereas humic acid (HA) had an inhibitory effect on Et-PABA removal. Six intermediates were identified based on HPLC–MS and degradation pathways were then proposed. It can be foreseen that the UV/PDS oxidation process has broad application prospects in water treatment. Full article