Use of differential spectroscopy to evaluate the structure and reactivity of humics

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.