Characterization of humic substances: Implications for trihalomethane formation

Abstract

Humic substances are precursors of carcinogenic trihalomethanes (THMs) formed during disinfection by chlorination in water treatment processes. In an effort to understand the relationship between trihalomethane formation potential (THMFP) and physicochemical properties of humic substances, UV-visible absorbance, fluorescence in emission and synchronous scan modes, and NMR spectra were measured for several aquatic fulvic and humic acids. For comparison, a soil fulvic acid was also examined using these methods. The feasibility of the gradient modified spin-echo (GOSE) NMR experiment to selectively measure singlet resonances arising from isolated protons was examined. In addition, diffusion coefficients were measured for DMSO solutions of the fulvic acids using BPPLED and GOSE-edited pulse sequences. Although none of the methods tested produced results that correlated with THMFP, the GOSE intensities determined for different regions of the NMR spectra did reflect the relative abundance of different types of functional groups produced by lignin oxidation. In addition, the GOSE-edited diffusion results suggest that the isolated protons, those most reactive to chlorination, are more likely contained in the larger molecular weight fractions of fulvic acids.

Influence of the humification process on the properties of peat humic acids

“…The ratio E 4 /E 6 is often used to describe the extent of condensation of the aromatic C-containing structures; low ratios reflect high degrees of condensation of aromatics, while high ratios mean the presence of large quantities of aliphatic structures and low amounts of condensed aromatics (Chin et al, 1997). This ratio is also inversely related to the degree of aromaticity, particle size, molecular weight and acidity (Uyguner et al, 2004).…”

Estimation of Concentration of Dissolved Organic Matter from Sediment by using UV�CVisible Spectrophotometer

“…Ultraviolet (UV) absorption spectrophotometer is generally used to study various properties of the DOC, such as its aromaticity, hydrophobic content, and biodegradability [2,[10][11][12] because DOM have constitute such type of components which have capacity to absorb the ultraviolet light for example unsaturated aliphatic bonds and benzenoid type components [13,14]. Specific absorbance at different specific wavelengths has been used to measure the aromaticity, hydrophobic content, apparent molecular weight and size, and biodegradability [15][16][17][18].UV-absorbance is good surrogate the concentration of DOM specifically concentration of aromaticity in DOM at 254 nm absorbance [13,18].…”

Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms

“…A possible sink is the reaction with organic matter, which is well known from water disinfection (e.g. Gallard and von Gunten, 2002;Uyguner et al, 2004). Voudrias et al (1985) report the reaction of phenolic compounds like phenol, catechol, and guaiacol with free chlorine by drinking water treatment processes and the formation of chlorinated aromatic compounds.…”

“…They suggested that these high values could result from the interaction of Cl ·− 2 with carboxylic acid functional groups of humic acids. THM formation from the reaction of molecular chlorine with humic substances was measured by Uyguner et al (2004) in water-treatment processes. Schöler and Thiemann (2005) report the natural formation of THM in the marine and terrestrial environment.…”