Insights into the sunlight-Induced photodegradation mechanisms of methamphetamine in surface water driven by NO₃⁻, HCO₃⁻ and Fe3.

Psychoactive substances abuse is a global issue, with the methamphetamine (METH) being the most used and produced illicit substance in recent years. METH has been recognized as emerging contaminants in aquatic ecosystems. Research on the removal of METH from surface water is still lacking in-depth exploration. The effects of key aqueous environmental factors on the photodegradation of METH were investigated in this study. NO₃⁻, Fe3+ and dissolved organic matter (DOM) enhanced the photodegradation of METH, respectively, with degradation rates increasing as their concentrations increased. When HCO₃⁻ coexisted with NO₃⁻, it exhibited dual effects on METH photodegradation: low concentrations inhibited the process, whereas high concentrations promoted it. The primary photodegradation products of METH, such as OH-METH, (OH)2-METH, AMP and NO2-OH-METH, were identified. The latter two compounds were newly discovered in this study. The mechanism of NO₃⁻, HCO₃⁻ and Fe3+ accelerating the photodegradation of METH in water was proposed to proceed via the generation of hydroxyl radical (HO∙), leading to the oxidation of METH, along with the involvement of nitro radical (∙NO2) and carbonate radical (CO3•-).