Application of fluorescence spectroscopy in the studies of natural organic matter fractions reactivity with chlorine dioxide and ozone

The composition of natural organic matter (NOM) fractions before and after the reaction with chlorine dioxide as well as ozone was studied by means of total luminescence spectroscopy (TLS) and synchronous scanning fluorescence measurements. The excitation–emission matrices spectra (EEMs) of natural as well as oxidised NOM fractions revealed two well-resolved bands with maxima at Ex/Em of 250–265/422–452 nm and at Ex/Em 300–336/414–446 nm ascribed to humic and fulvic material. The study of emission and synchronous spectra also confirmed the presence of protein-like constituents in all examined NOM fractions. The study of EEMs proved, that oxidation of all NOM fractions with ClO2 caused mainly the break-up of molecules into smaller fragments and a decrease of the aromaticity. Changes in EEMs after the oxidation of individual NOM fractions with O3 confirmed the formation of a significant amount of ozonation by-products, i.e. carboxylic acids, aldehydes and ketones during the oxidation process. In addition, the fluorescence studies confirmed relatively high reactivity of all NOM fractions with ClO2 as well as with ozone.