Characterization of Disinfection By-Products from Chromatographically Isolated NOM through High-Resolution Mass Spectrometry

Abstract

As levels of natural organic matter (NOM) in surface water rise, the minimization of potentially harmful disinfection by-products (DBPs) becomes increasingly critical. Here, we introduce the advantage that chromatographic prefractionation brings to investigating compositional changes to NOM caused by chlorination. Fractionation reduces complexity, making it easier to observe changes and attribute them to specific components. Under the conditions tested (0.1-0.4 g of Cl to g of C without further additives), the differences between highly and less oxidized NOM were striking. Highly oxidized NOM formed more diverse Cl-containing DPB, had a higher propensity to react with multiple Cl, and tended to transform so drastically as to no longer be amenable to electrospray-ionization mass spectral detection. Less-oxidized material tended to incorporate one Cl and retain its humiclike composition. N-containing, lipidlike, and condensed aromatic structure (CAS)-like NOM were selectively enriched in mass spectra, suggesting that such components do not react as extensively with NaOCl as their counterparts. Carbohydrate-like NOM, conversely, was selectively removed from spectra by chlorination.

Waterworks-specific composition of drinking water disinfection by-products

“…S3 and S4). When comparing with a previous fractionation study (ESI † Table S5), this description of FT-ICR MS amenable DBPs is consistent with DBPs formed after chlorination of two distinct NOM fractions, 14 one characterized by aromatic compounds with high oxygen content (e.g. polyphenol-like compounds) and the other by compounds with larger carbon-skeletons, typically having more double bonds than oxygen atoms (e.g.…”

“…Previous chlorination experiments on isolated NOM fractions prior to FT-ICR MS detection, showed that a fraction constituting oxygenated, unsaturated compounds was the only fraction producing DBPs with multiple chlorine atoms, indicating that these differences also are linked to NOM characteristics. 14,36 When comparing those CHOCl 2 formulae with the CHOCl 2 formulae found in this study, 12 of 65 DBP formulae were common, indicating that part of the CHOCl 2 formulae detected in this study was formed through reaction with similar precursors. 14 The bromide concentration in the raw water at MAL was 0.28 mg L −1 , i.e.…”

“…14,36 When comparing those CHOCl 2 formulae with the CHOCl 2 formulae found in this study, 12 of 65 DBP formulae were common, indicating that part of the CHOCl 2 formulae detected in this study was formed through reaction with similar precursors. 14 The bromide concentration in the raw water at MAL was 0.28 mg L −1 , i.e. substantially higher compared to the other waterworks, explaining the formation of elevated levels of brominated DBPs there.…”

“…12 Recent work summarizing the challenges and opportunities within DBP research points towards the need of finding the key "toxicity drivers" that can explain the observed risk for bladder cancer, so that efforts to minimize exposure focus on the relevant targets. 13 A number of studies have been carried out to analyze the non-volatile fraction of DBPs using nontarget approaches, where some have focused on lab experiments, [14][15][16][17][18] and a few on real waterworks. [19][20][21] Previous studies indicate that there is variation and overlap of nonvolatile DBPs formed at different waterworks.…”

Benefits of multidimensional fractionation for the study and characterization of natural organic matter

“…[18] We also demonstrated that fractionating NOM prior to investigating NOM's interaction with other chemicals (i.e., NaOCl added during water treatment) provides far more definitive results than analyzing bulk NOM. [33] In short, combined chromatographic prefractionation and multiple information-rich analyses have the potential to provide unprecedented structural insight. Structural insight allows more accurate predictions of structure-activity relationships in environmental, pharmacological, toxicological and industrial settings.…”