Uncovering tert -Butylphenols as New Precursors of 2,4,6-Trichlorophenol in Chlorinated Drinking Water

Abstract

2,4,6-Trichlorophenol is a well-known carcinogen, aromatic disinfection byproduct (DBP), and anthropogenic contaminant in drinking water, with a high detection frequency and concentration. Natural organic matter (NOM) is considered as its key precursor; however, the formation potential of NOM to 2,4,6-trichlorophenol during chlorination does not explain the μg/L levels observed in disinfected drinking water. In this study, concentrations of 2,4,6-trichlorophenol in drinking water from South Carolina were determined, and important new tert-butylphenol precursors were identified using nontarget and suspect screening analysis with gas chromatography (GC)-mass spectrometry (MS). Concentrations of 2,4,6-trichlorophenol in 12 chlorinated and chloraminated drinking water samples ranged from 9 to 14,966 ng/L (mean: 4805 ng/L), higher than 11 other classes of aromatic DBPs and 4 classes of aliphatic DBPs. During chlorination, yields of 2,4,6-trichlorophenol from Suwannee River NOM were 22 ng/mg-total organic carbon (TOC). In contrast, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, and 2,6-di-tert-butylphenol, found up to 41,037 ng/L in river water as industrial contaminants, showed yields of 737, 711, 1261, and 2939 ng/mg-TOC, respectively. tert-Butylphenols in source water contributed ∼3% of 2,4,6-trichlorophenol in the studied chlorinated river waters. Formation mechanisms were proposed. This study provides insight into uncovering additional unknown precursors of chlorophenols.