Chlorination of humic materials: byproduct formation and chemical interpretations

Humic and fulvic acids were extracted from humic material taken from five lakes or rivers. These acids were then reacted with chlorine, and yields of total organic halide (TOX) and several specific organohalides were measured under neutral and highly acidic conditions. With the exception of 1,1,1-trichloracetone, production of all measured organohalides was higher for aquatic humic acids than for fulvic acids coming from the same source. The nitrogen content of humic acids caused them to use more chlorine and produce more TOX, but fulvic acid produced TOX, using less chlorine. Models using carbon-13 nuclear magnetic resonance and base titrations demonstrated that activated aromatic centers are responsible for chlorine consumption. In samples with higher ultraviolet absorbance, formation of trichloroacetic acid was favored over other trihalomethanes. Chlorination under highly acidic conditions resulted TOX values of about half those chlorinated under neutral conditions.