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Natural organic matter (NOM) represents the major source of precursors for disinfection byproducts (DBPs), such as trihalomethanes (THMs) and haloacetic acids (HAAs), formed during disinfection of drinking water, but the molecular composition and reactivity of NOM remain not well understood. In this study, electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to characterize the molecular composition of NOM of 20 source waters taken across China for the purpose of determining the major precursors of THMs and HAAs at molecular level. It was found that there is a core of NOM compositions that are ubiquitous in different source waters, which is supposed to be more relevant for NOM quality. Formation potentials (FP) of THMs and HAAs were determined for NOM from different source waters during chlorination. Spearman's rank correlation was used to link THMFP and HAAFP with the individual molecular composition of NOM. Significant correlation (P < 0.001) was found between DBPFP and the NOM molecules with a high O/C ratio and low H/C ratio, indicating these molecules could contribute greatly to the formation of THMs and HAAs during chlorination. The link of THMFP and HAAFP with individual NOM molecules may allow us to develop more effective treatment strategies to achieve the drinking water safety objective: effective disinfection of waterborne pathogens while minimizing toxic DBPs. [ABSTRACT FROM AUTHOR]

Natural organic matter (NOM) can affect the performance of water treatment processes, and serves as a main precursor for the formation of disinfection byproduct (DBPs) during chlorination. To minimize such undesirable effects, a better understanding of its structural information and reactivity toward chlorine is necessary. In this study, electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was used to study the molecular composition of NOM in source water. More than four thousand NOM components were resolved in the sample. NOM molecules with a low degree of oxidation (low O/C ratio) were found to be more reactive toward chlorine than those with high O/C ratio. Totally, 659 one-chlorine containing products and 348 two-chlorine containing products were detected in the chlorinated sample at a high confidence level. The chlorinated products can be arranged into series, which indicate they were originated from precursor compounds in series related by the replacement of CH4 against oxygen. Of the 1007 chlorine-containing products observed in this study, only 7 molecular formulas can be found in previous studies, showing the distinct difference from previous studies. This study explored the reactivity of NOM toward chlorine on a molecular level, which was previously explained on the level of whole mixtures or fractions of NOM, and the identified chlorinated products may contribute to our knowledge of the unknown total organic halide (TOX). [ABSTRACT FROM AUTHOR]