Does climbazole instigate a threat in the environment as persistent, mobile and toxic compound? Unveiling the occurrence and potential ecological risks of its phototransformation products in the water cycle

Advanced oxidation coupled with LC-HRMS: Elucidating transformation products of linezolid, discovering in wastewaters and conducting in silico toxicity assessments

Antibiotics are prevalent in wastewater treatment plants and are subsequently released into aquatic environments, threatening aquatic organisms and compromising drinking water quality. Consequently, investigating their environmental fate and developing efficient removal processes is crucial. The degradation and fate of the antibiotic drug linezolid were investigated, focusing on the formation of transformation products (TPs). Various advanced oxidation processes, such as UV/S2O82-, UV/TiO2, Fe2+/S2O82- and UV/Fe2+/S2O82-, proved effective in eliminating linezolid within minutes. Liquid chromatography coupled to high-resolution mass spectrometry was employed to elucidate the photo-generated TPs and propose tentative transformation pathways. Overall, 28 TPs were identified, with 17 elucidated for the first time herein. The fluorophenyl and morpholine rings of the linezolid molecule were the main sites of attack, leading to two primary transformation routes: defluorination and hydroxylation. The predominant route varied with the treatment applied. In silico toxicity assessment indicated alarming toxicity for two TPs but decreased toxicity for most TPs compared to linezolid, suggesting the detoxification role of the treatments. However, concerning predictions emerged for the carcinogenicity, mutagenicity and biodegradability of linezolid and its TPs. Finally, a suspect screening analysis investigated the presence of TPs in wastewaters, revealing the occurrence of three TPs at notable levels, primarily in effluents.

Typical emerging contaminants in sewage treatment plant effluent, and related watersheds in the Pearl River Basin: Ecological risks and source identification

Emerging contaminants pose a potential risk to aquatic ecosystems in the Pearl River Basin, China, owing to the high population density and active industry. This study investigated samples from eight sewage treatment plants, and five surface water bodies of related watersheds. To screen the risk of emerging contaminants (ECs), and clarify their sources, this study calculated the risk quotient of detected chemical and performed source identification/apportionment using the positive matrix factorization method. In total, 149 organic pollutants were identified. Pharmaceuticals showed significant concentrations in sewage treatment plant samples (120.87 ng/L), compared with surface water samples (1.13 ng/L). The ecological risk assessment identified three chemicals with a heightened risk to aquatic organisms: fipronil sulfide, caffeine, and roxithromycin. Four principal sources of contaminants were identified: pharmaceutical wastewater, domestic sewage, medical effluent, and agricultural runoff. Pharmaceutical wastewater was the primary contributor (60.4 %), to the cumulative EC concentration and to ECs in sewage treatment plant effluent. Agricultural drainage was the main source of ECs in surface water. This study provides a strategy to obtain comprehensive information on the aquatic risks and potential sources of EC species in areas affected by artificial activities, which is of substantial importance to pollutant management and control.

Aqueous fate of furaltadone: Kinetics, high-resolution mass spectrometry - based elucidation and toxicity assessment of photoproducts

Furaltadone (FTD) is an antibiotic belonging to the nitrofurans group. It has been broadly used in livestock and aquaculture for therapeutic purposes, as well as for stimulating promotion. Although the European Union has imposed restrictions on the use of FTD since 1995 due to concerns regarding its toxicity, in many cases FTD has been excessively and/or illegally applied in productive animals in developing countries, because of its high efficacy and low-cost. Unlike other nitrofuran compounds, the hydrolytic and photolytic behavior of FTD in natural aquatic systems has not been thoroughly investigated. To this end, hydrolysis in different pH values and photolysis in aquatic environment, including lake, river and sea water have been both examined. Hydrolysis was found to have an insignificant impact on degradation of FTD in the aquatic environment relevant pH values, whereas indirect photolysis proved to be the main route of its elimination. The identification of tentative photoproducts (PPs) was performed using ultra high performance liquid chromatography coupled to hybrid LTQ/Orbitrap high resolution mass spectrometry. A possible pathway for photolytic transformation of FTD was proposed. Additionally, in silico simulations were used to evaluate the toxicity such as the mutagenicity of FTD and PPs. Complementary to the low-cost and time-limited simulations, an in vitro method (Vibrio Fischeri bioluminescence) was also used to assess ecotoxicity.