Photochemical conversion of chlorinated phenolic substances in aquatic media as studied by AOX and Microtox tests

Six chlorophenolic substances were photochemically converted by illumination with xenon light. The AOX (adsorbable organic halogens) contents were determined after illumination for various periods. Pure chlorinated phenolic substances were readily detected by AOX. Both adsorbable and non-adsorbable chlorinated products were formed. Chloride analysis indicated that most (if not all) of the non-adsorbable products consisted of chloride ions. Microtox, a bacterial bioluminescence test, was used as a screening test for toxic properties of the photolysis products. Products from 2,4,6-trichlorophenol were more toxic than the original substance. Other compounds tested had less toxic products as measured by their combined effect on the Microtox system. Products of 2,4-dichlorophenol, 2,3,4-trichlorophenol, 4,5,6-trichloroguaiacol and 2,3,4,5-tetrachlorophenol did not seem to contribute to the combined toxic properties after partial photolysis of the parent compound. Pentachlorophenol was converted into products which had substantial effects on the Microtox system.