Characterization of brominated disinfection byproducts formed during chloramination of fulvic acid in the presence of bromide

To date, study on the speciation of brominated disinfection byproducts (Br-DBPs), which have higher cytotoxicity and genotoxicity than their analogous chlorinated DBPs (Cl-DBPs), formed in chloramination is still limited. In this study, the previous unknown Br-DBPs formed during chloramination of artificial drinking water were explored with electrospray ionization ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). In total, 193 formulae of one bromine containing Br-DBPs and 5 formulae of two bromine containing Br-DBPs were detected in the chloraminated artificial drinking water sample. Compared to Br-DBPs formed in chlorination, Br-DBPs formed in chloramination have relatively high O/C ratio for the same nominal molecular mass. More than 63% of the Br-DBPs formed during chloramination can be classified as aromatic molecules or polycyclic aromatic molecules, according to their modified aromaticity index (AImod). Further investigation on the change of precursor SRFA molecules during chloramination showed that SRFA molecules with high O/C ratio and low H/C ratio were more reactive and decreased significantly in relative abundance during chloramination. Precursor SRFA molecules with high degree of oxidation and high unsaturation were preferred to form Br-DBPs during chloramination. The results reported in this study provide valuable information on Br-DBPs formed during chloramination and may help us in minimizing DBPs during chloramination.