title: Role of humic substances in the degradation pathways and residual antibacterial activity during the photodecomposition of the antibiotic ciprofloxacin in water.
abstract: This study focuses on the photo-transformation, in presence of humic substances (HSs), of ciprofloxacin (CIP), a commonly-used fluoroquinolone antibiotic whose presence in aquatic ecosystems is a health hazard for humans and other living organisms. HSs from the International Humic Substances Society (Elliott humic acid and fulvic acid, Pahokee peat humic acid and Nordic lake) and a humic acid extracted from modified coal (HACM) were tested for their ability to photodegrade CIP. Based on kinetic and analytical studies, it was possible to establish an accelerating effect on the rate of CIP decomposition caused by the humic substances. This effect was associated with the photosensitized capacity of the HSs to facilitate energy transfer from an excited humic state to the ground state of ciprofloxacin. Except for Nordic lake, which experienced a lower positive effect, no significant differences in the CIP transformation were found among the different humic acids examined. The photochemistry of CIP can be modified by parameters such as pH, CIP or oxygen concentration. The irradiation of this antibiotic in the presence of HACM showed that antimicrobial activity was negligible after 14 h for E. coli and 24 h for S. aureus. In contrast, the antimicrobial activity was only slightly decreased after 24 h of irradiation by direct photolysis. Although mineralization of CIP irradiation in the presence of a HACM solution was not achieved, biodegradability was achieved after 12 h of irradiation, indicating that microorganisms within the environment can easily degrade CIP photochemical by-products.
authors.affiliation: Química de Recursos Energéticos y Medio Ambiente, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia.
authors.forename: Jazmín
authors.initials: J
authors.lastname: Porras
authors.affiliation: Grupo de Investigación en Remediación Ambiental y Biocatálisis, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia.
authors.forename: Cristina
authors.initials: C
authors.lastname: Bedoya
authors.affiliation: Grupo de Investigación en Remediación Ambiental y Biocatálisis, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia.
authors.forename: Javier
authors.initials: J
authors.lastname: Silva-Agredo
authors.affiliation: Química de Recursos Energéticos y Medio Ambiente, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia.
authors.forename: Alexander
authors.initials: A
authors.lastname: Santamaría
authors.affiliation: Química de Recursos Energéticos y Medio Ambiente, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia. Electronic address: john.fernandez@udea.edu.co.
authors.forename: Jhon J
authors.initials: JJ
authors.lastname: Fernández
authors.affiliation: Grupo de Investigación en Remediación Ambiental y Biocatálisis, Instituto de Química, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia. Electronic address: ricardo.torres@udea.edu.co.
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Torres-Palma
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001578:Benzopyrans / Q000737:chemistry; D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D002939:Ciprofloxacin / Q000737:chemistry*; D004926:Escherichia coli / Q000187:drug effects; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015394:Molecular Structure; D010782:Photolysis; D013211:Staphylococcus aureus / Q000187:drug effects; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D001578:Benzopyrans; D006812:Humic Substances; D014874:Water Pollutants, Chemical; D002939:Ciprofloxacin; C005023:fulvic acid
keywords: Antibiotics; Degradation routes; Fluoroquinolones; Photochemical treatment; Water treatment