Environmental Fate of 2-Fluorobiphenyl and 1-Bromo-4-Fluorobenzene: Evaluating Pathways and the Transformation Products in Sunlit Surface Waters

• Grant number: 25/09729-0
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: September 01, 2025
• End date: December 31, 2025
• Field of knowledge: Engineering - Chemical Engineering
• Principal Investigator: Antonio Carlos Silva Costa Teixeira
• Grantee: Leticia Dietrich
• Supervisor: Scott Mabury
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: University of Toronto (U of T), Canada
• Associated to the scholarship: 24/21523-6 - PIRACICABA, CAPIVARI AND JUNDIAÍ RIVER BASIN UNDER THE IMPACT OF POLLUTANTS OF EMERGING CONCERN: AN ENVIRONMENTAL PERSISTENCE STUDY, BP.MS

Abstract

This study aims to investigate the photochemical degradation pathways of two halogenated aromatic contaminants - 2-fluorobiphenyl (2-FB) and 1-bromo-4-fluorobenzene (pBFB) - in sunlit natural aquatic environments. These contaminants of emerging concern (CEC) have been detected in Brazilian surface waters and, due to their chemical properties and usage, are likely present in other regions worldwide. However, their environmental fate remains poorly understood. For poorly biodegradable pollutants, sunlight-induced photochemical processes, such as direct and indirect photolysis, play a key role in their removal from surface waters. Direct photolysis occurs when CEC absorb UV-visible radiation and degrade, while indirect photolysis involves the oxidation of pollutants by photoproduced reactive intermediates (hydroxyl radicals, HO*; carbonate radicals, CO3*-; singlet oxygen, 1O2; and triplet excited states of chromophoric dissolved organic matter, 3CDOM*), generated by the absorption of sunlight by inorganic and organic compounds present in water. To address this gap, this project proposes a research exchange at the University of Toronto, under the supervision of Prof. Scott Mabury, a leading expert in the study of environmental fate of CEC and transformation products, particularly for halogenated organics. The study will apply the PhotoFate methodology to simulate natural photochemical conditions while varying key water quality parameters such as nitrate, dissolved organic matter, and bicarbonate concentrations. The project objectives are to: (1) quantify degradation kinetics under different environmental scenarios; (2) identify and characterize transformation products using GC-MS, LC-MS/MS, and 19F NMR; (3) determine the relative contributions of various reactive species (HO*, 1O2, CO3-*, 3CDOM*); and (4) assess the environmental mobility and ecotoxicity of degradation products through Quantitative Structure-Activity Relationship (QSAR) predictions. Using advanced analytical instrumentation available in Prof. Mabury's laboratory, the experiments will allow the identification of transformation products and the quantification of degradation rates under variable conditions. Our findings will provide critical insights into the persistence and transformation of these contaminants into aquatic systems, addressing a significant knowledge gap in environmental chemistry. (AU)