Fate of aromatic sulfonates in fluvial environment

Water samples of the Italian river Bormida, which is polluted by the wastes of the production of azo-dyestuff intermediates, were analysed by FAB/MS and the resulting data were compared to those obtained by HPLC. The presence of sulfonated derivatives of naphthalene was confirmed but, in addition, several sulfonated compounds having molecular mass other than those of naphthalenesulfonates (NS) were also found. Those compounds were suspected of originating from oxidative degradation of NS's. Laboratory tests showed that some NS's indeed can undergo oxidative degradation under physico-chemical conditions similar to those occurring in a river. In particular, the dark-coloured degradation products of 1-hydroxy-2-naphthalenesulfonic acid appeared similar to an unknown compound found in the river water.