Photobleaching-induced changes in photosensitizing properties of dissolved organic matter



Photosensitizing properties of different dissolved organic matter (DOM) were investigated according to their performance in singlet oxygen (1O2), triplet state of DOM (3DOM*), and hydroxyl radical (.OH) productions. The photobleaching of DOM solutions after irradiation was characterized by fluorescence excitation-emission matrix and UV-Vis spectroscopy.
The photosensitizing properties of pre-irradiated DOM solutions were changed in a sunlight simulator. The performance of DOMs in photosensitized degradation of several contaminants was investigated. For a 20 h exposure, the observed degradation rate constant (kobs) of some contaminants decreased as a function of exposure time, and highly depended on the properties of both DOM and contaminant. Degradation of contaminants with lower hob was more susceptible to DOM photobleaching-induced decrease in kobs. Under the current experimental conditions, the photobleaching-induced decrease of DOM photo-reactivity in contaminant degradation was mainly attributed to indirect phototransformation of DOM caused by the interactions between photo-inductive DOM moieties and photochemically-produced reactive species. Reactive contaminants can inhibit DOM indirect photobleaching by scavenging reactive species, photosensitized degradation of these contaminants exhibited a stable kobs as a result. This is the first study to report DOM photobleaching-induced changes in the simultaneous DOM photosensitized degradation of contaminants and the inhibitory effect of reactive contaminants on DOM photobleaching.

Copyright © 2014 Published by Elsevier Ltd.

Sobre el autor

Leonardo Gutiérrez

Dr. Gutierrez is an expert in AFM studies and has extensive experience in the field of colloidal/interfacial chemistry. He applies sophisticated AFM experimental techniques that aid in the elucidation of the dominant interacting mechanisms between organic compounds and colloids, including viruses, bacteria, and surfaces. His core training at the Seitz Materials Research Laboratory (UIUC) included: (Cryo) Transmission electron microscopy, (Environmental) Scanning electron microscopy, Fluorescence correlation spectroscopy, (Time-Resolved) Dynamic Light Scattering, and Streaming (Zeta) Potential-Electrophoretic mobility measurements. In addition, Dr. Gutierrez received specialized training in bio-safety (Vet-Med School at UIUC) levels 1 and 2 (handling/growing/purification of pathogens, bacteria, viruses, phages, and cell stocks), Atomic Force Microscopy (AFM-contact and tapping mode) coupled with Raman Spectroscopy, Quartz crystal microbalance with dissipation technique, and Synchrotron-based Small Angle X-Ray scattering. His investigations have been conducted along with multidisciplinary teams of prestigious Universities and National Labs (e.g., Yale University, King Abdullah University of Science and Technology KAUST, Argonne National Lab at Chicago, SLAC National Accelerator Laboratory at Stanford University, Curtin University of Technology, etc.). All his research projects resulted in publications in international peer-reviewed journals (e.g. ES&T, Water Research, Langmuir, Soft Matter, etc.), and have been presented in international conferences (e.g. American Chemical Society, Materials Research Society, Association of Environmental Engineering and Science Professors, etc.). Dr. Gutierrez is currently holding a Full-Professor position at Universidad del Pacifico (Ecuador), where he develops characterization techniques at the nano-scale.

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