Chlorination of ozonated soil fulvic acid: mutagenicity studies in Salmonella.

Samples of soil fulvic acid (SFA) were ozonated and subsequently chlorinated under acidic or slightly basic conditions. The residues were tested for His+ reversion in a fluctuation assay, using Salmonella typhimurium TA100 as the tester strain. The ozonated/chlorinated samples were mutagenic, but activity was dependent on the amount of ozone utilized and the pH of the reaction medium. Although increases in cell concentrations were also induced by some mutagenic samples, this alone did not account for the mutagenicity observed. Unchlorinated samples displayed insignificant activity.