Characterization of Brominated Disinfection Byproducts Formed During the Chlorination of Aquaculture Seawater

Although brominated disinfection byproducts (Br-DBPs) have been reported to form from reactions between bromide, dissolved organic matter (DOM), and disinfectants, their formation during the disinfection of aquaculture seawater via chlorination has been rarely studied. Herein, after 5 days of disinfection of raw aquaculture seawater samples with sodium dichloroisocyanurate (NaDDC), trichloroisocyanuric acid (TCCA) and chlorine dioxide (ClO2), 181, 179, and 37 Br-DBPs were characterized by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Sunlight irradiation of the chlorinated aquaculture seawater with TCCA and NaDDC was found to reduce the formation of Br-DBPs, possibly due to the photodegradation of the important HBrO/HClO intermediate and the degradation of formed Br-DBPs. The formation of Br-DBPs chlorinated by ClO2 increased under sunlight irradiation. The number of Br-DBPs formed during chlorination processes agreed well with the total organic bromine (TOBr) content measured by inductively coupled plasma mass spectrometry (ICP-MS). Most of the Br-DBPs were highly unsaturated and phenolic compounds, which were primarily generated through electrophilic substitution by bromine coupled with other reactions. In addition, some emerging aromatic Br-DBPs with high relative intensities were also assigned, and these compounds might be highly lipophilic and could potentially accumulate in marine organisms. Our findings call for further focus on and investigation of the Br-DBPs produced in chlorinated aquaculture seawater.