Development of dual probe reactivity-directed analysis (DP-RDA) for the identification of toxic amine-/thiol-reactive disinfection byproducts in treated drinking water

Disinfection is a crucial process for effectively preventing waterborne diseases from spreading in water supplies to human communities. However, during the reaction between disinfectants and impurities in source water, harmful disinfection by-products (DBPs) can form. While many DBPs are known, and some are recognized as carcinogens, a significant number of DBPs remain unidentified. Therefore, high priority should be given to identifying DBPs that are inherently toxic, or that might be further converted into other hazardous byproducts upon water disinfection. In this study, a pioneering biomimetic approach – dual probe reactivity-directed analysis (DP-RDA), combining i) amine-and thiol-reactivity and ii) high-resolution mass spectrometry – is proposed for the identification, characterization and prioritization of unknown toxic DBPs generated in disinfected water. Amines and thiols represent the nucleophilic sites that can be bound by electrophiles (i.e., reactive DBPs), and their reactivites are toxicologically meaningful and well correlated with toxicities of DBPs.

While the current single probe-RDA approaches do enhance the “visibility” of unknown toxic DBPs, the number of unidentified DBPs that can be captured is limited by the unique chemical properties of a single probe. In contrast, the DP-RDA method can not only capture both amine-reactive and thiol-reactive DBPs, but also reveal the previously overlooked hazardous DBPs. Given the structural variability of natural organic matter (NOM) in our source waters, it is likely that numerous emerging DBPs are generated during water disinfection. In order to advance our understanding of the impacts of these unidentified DBPs on water safety, we need to investigate: (a) the effects of different organic matter as precursors of amine-/thiol-reactive DBPs; (b) their formation mechanisms; and (c) their occurrence in our drinking water.

To respond to these concerns, this work will first develop a DP-RDA-based technique, integrating the use of both amine and thiol probes to specifically detect and trace these harmful DBPs formed during water disinfection. The formation mechanism of these emerging DBPs will then be investigated using different types of selected precursors and NOM upon chlor(am)ination. A comprehensive occurrence study of these emerging DBPs in the Greater Bay Area (Hong Kong and Shenzhen) and Barcelona will also be conducted, utilizing the developed method for examining drinking water samples. The chemical data produced in this study will contribute to the fundamental understanding of the formation of toxic emerging DBPs through chlor(am)ination. This work will significantly advance our ability to keep our drinking water safe and our ecosystems healthy.