Interactions of chlorine with natural organic matter and formation of intermediates: evidence by differential spectroscopy

This communication describes the use of differential absorbance spectroscop y to explore the intermediates formed during halogenation of natural organi c matter (NOM). The differential spectra of chlorinated NOM comprise two co ntributions. The primary component is negative and has a peak near 270 nm. The shape of this band is independent of chlorine dose, and its intensity i ncreases monotonically with Cl-2 dose. The second component is positive, wi th a well-defined peak near 280 nm and another, broader band in the 340...3 80 nm range. The second component is noticeable at low chlorine concentrati ons but disappears with increasing Cl-2 dose. We attribute this component t o aromatic chlorinated intermediates formed prior to the release of identif iable smaller species such as haloacetic acids. We believe that this compon ent of the differential spectra can be used to probe the identity, formatio n and breakdown of the halogenated intermediates.