PHOTODEGRADATION OF THE SURFACTANTS NA-DODECYLBENZENESULFONATE AND DODECYLPYRIDINIUM-CHLORIDE AS AFFECTED BY HUMIC SUBSTANCES

Surfactants account for a great proportion of organic xenobiotica rele ased into the environment by anthropogenic action. In natural waters a nd sewage sludge they can be removed from solution by different reacti ons, including adsorption to solid phases, biodegradation and abiotic photolytic degradation. In the present investigation we found that pho todegradation of Na- dode-cylbenzenesulfonate (LAS) was reduced by hum ic substances by a factor of 2 or more. In contrast, photodegradation of dodecylpyridinium-chloride (LPC) was increased in the presence of h umic substances by a factor of 1.16-1.43. These differences were expla ined by the strong bonding of LPC but not of LAS to the humics. Photol ytic degradation of LAS begins at the aliphatic side chains followed b y aromatic ring cleavage. Photodegradation of LPC mainly associated wi th the humics showed similarity to that of pyridine. The experimental data demonstrate strong effects of photodegradation on the persistence of surfactants and the relevance of humic-surfactants associations fo r photolytic processes.