Quantifying the effects of chlorine disinfection on microplastics by time-resolved inductively coupled plasma-mass spectrometry

• Published in: The Science of the total environment 2024-12, Vol.954, p.176132, Article 176132
• Main Authors: Ho, Wai-Kit, Lum, Judy Tsz-Shan, Lam, Tsz-Ki, Yip, Tai-Nam, Hor, Catherine Hong-Huan, Leung, Kelvin Sze-Yin
• Format: Article
• Language: English
• Subjects: aquatic environment; cell death; cell viability; Characterization; chlorine; Chlorine disinfection; Cytotoxicity; disinfectants; disinfection; humans; Microplastics; polystyrenes; spectroscopy; Time-resolved ICP-MS; ultraviolet radiation; water supply; water treatment
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.176132

Using current water treatment systems, significant amounts of microplastics (MPs) are passing through and being released into the aquatic environment. However, we do not clearly know what effects disinfection processes have had on these particles. In this study, we applied inductively coupled plasma-mass spectrometry (ICP-MS) operating in time-resolved analysis (TRA) mode for quantifying changes in the chlorine (Cl) content of MPs under a variety of water treatment scenarios. Our results illustrated that time-resolved ICP-MS offers a potential method for sensitive and direct analysis of Cl content, including Cl mass and chlorine association (%Cl/C), of discrete particles in the MP suspension by the fast sequential measurements of signals from 35Cl1H2 and 12C1H. Our research, across various water treatment scenarios, also showed that polystyrene (PS) MPs exhibited greater reactivity to Cl disinfectant after being pre-disinfected with UV light and in mildly acidic to neutral pH environments. It is noteworthy that about half of the particles in MP suspension exposed to 10 mg Cl2/L, a typical Cl dose applied in water treatment, were chlorinated, and had a Cl content comparable to that of particles subjected to extreme conditions. Of even greater concern is the fact that our cell viability tests revealed that chlorinated MPs induced considerably higher rates of cell death in both human A549 and Caco-2 cells, and that the effects were Cl dose- and polymer type-dependent. Overall, this study demonstrates the potential of time-resolved ICP-MS as a valuable technique for quantifying the Cl content of MP particles, which is crucial to assessing the fate and transformation of MPs in our water supply and treatment systems. [Display omitted] •First report on the use of time-resolved ICP-MS in measuring the Cl content of MPs.•PSMPs became more susceptible to Cl reactivity after pre-disinfected with UV light.•Chlorination of MPs was favored in mildly acidic to neutral pH environments.•Performance of (TRA)ICP-MS, EDX, FTIR and XPS for Cl detection on MPs was compared.•Cl-disinfected MPs exerted higher cytotoxic effects on human A549 and Caco-2 cells.