DBP formation potential of aquatic humic substances

Terrestrial vegetation commonly shed into reservoirs contains chemical precursors of DBPs. Aquatic humic substances (AHSs) in water generate potentially harmful disinfection by‐products (DBPs) such as haloacetic acids (HAAs) and trihalomethanes (THMs) during chlorination. AHSs from two Arkansas reservoirs were characterized to define source, identify meta‐dihydroxybenzene (m‐DHB) structures as probable DBP precursors, and evaluate predicted HAA and THM formation potentials. Elemental nitrogen content < 1 percent, phenol content > 0.5 μeq/mg, δ 13 C values of –27% o , and low yields of syringyl phenols found by cupric oxide (CuO) oxidation suggest a pine tree source for the AHSs found in the Maumelle and Winona reservoirs in Little Rock, Ark. CuO oxidation yielded fewer m‐DHB structures in Maumelle AHSs than in Winona AHSs. A higher 3,5‐dihydroxybenzoic acid (3,5‐DHBA) content correlated with increased HAA and THM formation potential. The 3,5‐DHBA concentration in Winona AHSs was similar to the range found in AHSs extracted from deciduous leaf litter, twigs, and grass leachates.