Precursors for brominated haloacetic acids during chlorination and a new useful indicator for bromine substitution factor

Brominated haloacetic acids (HAAs) are much more cytotoxic and genotoxic than chlorinated one, yet little information is available for their organic precursors. In the present study, 8 water samples were collected in East China: 2 from lakes, 2 from rivers, 2 from reservoirs, a well and a mountain spring. Dissolved organic carbon (DOC), UV absorbance at 254 (UVA), specific UVA (SUVA) and chlorophyll a (Chl-a) were determined in raw water samples; formation of 9 HAA species as well as bromine substitution factor (BSF) were measured in chlorinated water samples. Results showed that water samples located in city generally contained higher levels of DOC (6.4-122 mg/L) and UVA (0.124-0.194/cm), while those in the country side, low DOC (2.4-5.9 mg/L) and UVA (0.061-0.109/cm) levels were observed. Negative relationship (p < 0.01) was found between SUVA values and Chl-a levels. Among 9 HAA species, 4 brominated HAA were detected. As for BAA and DBAA (i.e. Br-HAAs), their yields (m/L) were significant related (p < 0.05) with DOC: In terms of BCAA and BDCAA (i.e. ClBr-HAAs), they were not only related with DOC, but also with UVA. These two results were quite different from DCAA and TCAA (Cl-HAAs), whose yields (mu g/mg C) were only correlated with SUVA values, suggesting that precursors of Cl-HAA, Br-HAA and CIBr-HAA were different from each other, and their aromaticity/hydrophobicity may be in the order of Br-HAA < CIBr-HAA Interrelationship between Br/DOC, SUVA and BSF revealed that BSF can be influenced by SUVA and Br/DOC, but in comparison, Br/UVA was the best indicator to describe BSF. This pattern is not only true in di-HAAs and tri-HAAs in this study, but also valid in other water samples and other species of disinfection by-product (e.g. trihalomethanes, dihaloacetonitriles, trihalonitromethanes). (C) 2019 Elsevier B.V. All rights reserved.