Differential absorbance spectroscopy is a powerful tool for monitoring tran
sformations in the chemical state of humic species (HS). Differential spect
ra for halogenation of HS are remarkably similar for a wide range of raw an
d treated waters bur are dramatically different from those of model compoun
ds such as resorcinol. These differences might be related to the larger siz
e of the HS molecules and the consequent interchromophore interactions. The
shape of the spectra provides information about the chemical nature of the
reactive chromophores. The formation bf chlorinated disinfection by-produc
ts such as CHCl3 is strongly correlated with the magnitude of the different
ial absorbance. (C) 1999 Published by Elsevier Science Ltd on behalf of the
IAWQ. All rights reserved.