Humic Acids and Fulvic Acids: Characteristics, Sorption of Hydrophobic Organic Contaminants, and Formation of Disinfection by-Products during Chlorination

Humic and fulvic acids, which can be extracted from soils, are abundant in surface water because of their high discharges from runoff during torrential rainfall, storm events, and summer monsoon. Both humic and fulvic acids adversely affect water supply as they produce disinfection by-products (DBPs) during chlorination and serve as the sorbent for the binding of hydrophobic organic contaminants. In the present study, we conducted chlorination and phenanthrene sorption for humic and fulvic acids that were extracted from nine soil samples. We also analyzed and compared their characteristics by using elemental 13C NMR analysis, spectroscopy analysis, and size exclusion chromatography. Our results showed that the changes in their structural characteristic, their DBP formation, and phenanthrene sorption behavior differed critically between humic and fulvic acids. For chlorinated humic acids, high SUVA, low molecular weight, low N/C, and low O groups of aromatic C were associated with high trihalomethane (THM) formation. In comparison, low O groups of aliphatic C in fulvic acids were associated with both oxidation and incorporation in terms of THM formation. Humic acids exhibited higher sorption ability than fulvic acids due to their higher MWw, SUVA, and %THLF. These findings provide key information for monitoring water quality in rivers and lakes