Molecular characteristics of halogenated disinfection byproducts elucidated by Fourier transform ion cyclotron resonance mass spectrometry.

Dissolved organic matter is the main precursor for the formation of halogenated disinfection by-products (X-DBPs) during the disinfection of drinking water. However, the majority of the X-DBPs identified based on the artificially prepared water using the Suwannee River Natural Organic Matter (SRNOM) will bias the assessment of X-DBP formation potential in actual natural water. Herein, the non-targeted analysis based on ultrahigh-resolution mass spectrometry was employed to reveal the discrepancy in the molecular composition of X-DBPs and their precursors in SRNOM solution and actual authentic samples during disinfection. The X-DBP precursors in the chlorinated authentic samples were more saturated and reductive but less oxidative and aromatic than those in the chlorinated SRNOM. Lignin-like compounds represented the predominant chemical composition of X-DBPs and their precursors in all samples. Unlike SRNOM, the oxygen-rich and hydrogen-poor X-DBPs and their precursors in authentic samples were enriched in hydrogen-rich and oxygen-poor compounds. In addition, successive neutral losses of HOCl/HOBr observed in collision-induced dissociation MS-MS spectra of X-DBPs further demonstrated the formation of X-DBPs. The optimum chemical structures of three typical X-DBPs, namely CHONBr, CHOBr, and CHONSBr, were annotated as 3,5-dibromo-1H-pyrazol-4-ol, 2,3-dibromosuccinic acid, and 2-((bromothio)oxy)-2-hydroxy-2H-azirin-3-yl hypobromite. This study provides new insights into a comprehensive understanding of the chemodiversity of X-DBPs and their precursors in environmental samples and standard substances after chlorination.