KINETIC STUDY OF THE PHOTOCHEMICAL PERSISTENCE OF THE LARVICIDE TEMEPHOS

• Grant number: 25/10775-7
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: September 01, 2025
• End date: December 31, 2025
• Field of knowledge: Engineering - Chemical Engineering
• Principal Investigator: Antonio Carlos Silva Costa Teixeira
• Grantee: Amanda Velho Guimarães
• Supervisor: Davide Vittorio Vione
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Università degli Studi di Torino (UNITO), Italy
• Associated to the scholarship: 24/12649-6 - KINETIC STUDY OF THE PHOTOCHEMICAL PERSISTENCE OF THE LARVICIDES TEMEPHOS AND N-TOSYLINDOL, BP.IC

Abstract

Worldwide, mosquito-borne diseases, and particularly dengue, represent a major public health concern, being primarily transmitted by the mosquito Aedes aegypti, whose larval development occurs in aquatic environments. Given the limited availability of vaccines with broad coverage, the main control strategy remains based on larval elimination through the use of larvicides. Among these, temephos stands out as one of the most widely used compounds for vector control. Considering that an effective larvicide must balance sufficient environmental persistence to ensure larval elimination with the minimization of potential impacts on aquatic ecosystems, this research internships abroad (BEPE) project aims to study the degradation kinetics of temephos mediated by the carbonate radical (CO3*-) in aqueous media, under simulated solar irradiation. The carbonate radical is a photochemically produced intermediate in surface waters, especially under alkaline conditions and high carbonate concentrations. Through controlled photodegradation experiments, this study aims to determine the second-order rate constant for the reaction between temephos and CO3*-. The CO3*- radical represents an addition to the reactive intermediates studied in the research project carried out by the student in Brazil, including singlet oxygen, hydroxyl radicals and triplet excited states of dissolved organic matter. The study also seeks to identify and characterize the transformation products (TPs) formed during the degradation process, focusing exclusively on those generated by the most reactive photosensitized primary reactive intermediates (PPRIs) identified in the system. The identification of TPs is fundamental to assessing whether the products generated are more or less persistent and potentially harmful than the parent compound. The results will contribute to understanding whether the degradation of temephos via this specific oxidative pathway (CO3*-) significantly affects its environmental fate in aquatic systems, providing key information for assessing the environmental persistence of temephos and its potential ecotoxicological risks. (AU)