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ABSTRACT
The main objective of this study was to determine the occurrence of polycyclic aromatic hydrocarbons (PAHs) in surface water samples collected from different points along the stream that flows through the Campus of the Federal University of Santa Maria, RS-Brazil. Before reaching the campus, the water in the stream is already contaminated by wastewater discharged from the surrounding, and once inside the Campus, additional wastewater from a Gas Station situated close to the University hospital. A bench scale photodegradation experiment was conducted of the occurring traces of anthracene, phenanthrene and naphthalene, with the aid of a stirred tank reactor and polymer-supported TiO2 as a catalyst. To prevent loss of the low soluble analytes, it was necessary to add 5% and 10% acetonitrile, as an organic modifier of the synthetic aqueous solutions and real samples, respectively. An experimental design was employed and the best conditions for the photocatalysis of the aqueous solutions and real samples were pH 9 and pH 7, and 35°C and 30°C, respectively. Under optimized conditions, the analytes were completely degraded after 60 min of irradiation. The subproducts of the photocatalysis were identified through gas chromatography/mass spectrometry, and fragmentation routes were proposed. The mean concentrations of PAHs in the polluted surface water and hospital wastewater were relatively high: 3.9 ± 1.7 and 21.5 ± 2.8 µg L−1, respectively. A preliminary risk assessment revealed that the presence of anthracene requires particular attention. The risk posed by the occurrence of PAHs in the surface water and hospital wastewater samples confirms the need for an efficient treatment system.
Acknowledgments
The authors would like to express their gratitude to the CNPQ (Brazilian National Council of Technological and Scientific Development), CAPES (Brazilian Federal Agency for Support and Evaluation of Graduate Education) and SWINDON (International Network on Sustainable Water Management in Developing Countries, TU Braunschweig, Germany) for its financial support and/or scholarships.
Supplementary Materials
Figure S1. Emission spectrum of the mercury vapor lamp used by the AOPs: (a) without protection and (b) with quartz cover protection.
Figure S2. Pareto diagrams for the photodegradation of PAHs in aqueous solution: (a) anthracene, (b) naphthalene.
Figure S3. Pareto diagrams for the photodegradation of PAHs in hospital wastewater: (a) anthracene, (b) naphthalene, (c) phenanthrene.
Figure S4. Mass spectra of subproducts resulting from the photocatalytic degradation of anthracene in aqueous solution.
Figure S5. Mass spectra of subproducts resulting from the photocatalytic degradation of anthracene in surface water samples.
Figure S6. Mass spectra of subproducts resulting from the photocatalytic degradation of anthracene in hospital wastewater samples.
Figure S7. Mass spectra of subproducts resulting from photocatalytic degradation of phenanthrene in aqueous solution.
Figure S8. Mass spectra of subproducts resulting from photocatalytic degradation of phenanthrene in surface water samples.
Figure S9. Mass spectra of subproducts resulting from photocatalytic degradation of phenanthrene in hospital wastewater samples.
Figure S10. Mass spectra of subproducts resulting from photocatalytic degradation of naphthalene in aqueous solution.
Figure S11. Mass spectra of subproducts resulting from photocatalytic degradation of naphthalene in surface water samples.
Figure S12. Mass spectra of subproducts resulting from photocatalytic degradation of naphthalene in surface water samples.
Table S1. Matrix planning, independent variables and results of the PAHs degradation by heterogeneous photocatalysis in aqueous solution.
Table S2. Matrix planning, independent variables and results of the PAHs degradation by heterogeneous photocatalysis in wastewater samples.