Photochemical Aging of Lab-Generated Triclosan Aerosols in the Presence of •OH and Salts

DIANA TRAN, Jonathan Slade, University of California, San Diego

     Abstract Number: 502
     Working Group: Aerosol Chemistry

Abstract
Antimicrobial additives, such as Triclosan (5-chloro-2-(2,4-dichloro phenoxy) phenol; TCS), are toxic and accumulate in the environment due to their low solubility and frequent use in everyday household products. TCS may transfer into the aerosol phase at the air-water interface through wave-breaking and bubble-bursting mechanisms in lakes, oceans, and directly from wastewater treatment plants during aeration. Once in the aerosol phase, TCS is prone to photodegradation, producing toxic photoproducts, such as 2,8-dichlorodibenzo-p-dioxin (2,8-DCDD). Although regulated by the FDA, the photo-initiated transformation kinetics of TCS decay and dioxin formation in the aerosol phase, which may differ between bulk solution and surface water, have not been studied. As aerosols are transported in the atmosphere, they are susceptible to chemical aging reactions through interactions with light and oxidants, such as ·OH. This study focuses on the degradation of aerosol-phase TCS by irradiation in the presence of isopropyl nitrite (IPN), forming ·OH and NO_x (NO+NO₂), and with or without salts mimicking fresh (CaCO₃) and saltwater (NaCl) aerosols. Photochemical aging was conducted in a potential aerosol mass oxidative flow reactor (PAM-OFR) equipped with two 369 nm lamps. TCS and 2,8-DCDD in aerosols were monitored in near real-time with an extractive electrospray ionization high-resolution mass spectrometer (EESI-HRMS). Product analysis was conducted additionally with GC-MS. TCS signal in the presence of IPN showed a greater signal decay, indicating the presence of ·OH may be enhancing the degradation of TCS over time. Effects of varying NO_x, O₃, and temperature in the PAM-OFR on TCS will also be discussed. This work ultimately contributes to a better understanding of TCS’s photodegradation kinetics in aerosols, which has implications for public health.