Adrian A Ammann*
Hydroxyl radicals (HO•) formation during the ligand stabilized iron redox cycling was investigated in synthetic media, expended algal growth media (Talaquil) and field collected fresh water. HO• were selectively reacted in situ with terephthalic acid producing hydroxyterephthalic acid, quantified by fluorescence. FeIIIEDTA, photoreactive in dim light, was used as a control to compare how media components influence HO• formation rates. Since HO• is highly reactive, transformation depends on to the number of reactive atoms in a media component. Protoporphyrin IX accelerated HO• formation 20-fold, providing a good model for studying rate accelerating components of algae excretion. The results show that HO• production under usual algal test and natural fresh water conditions differ, the latter being more toxic. They enable more reliably comparison between natural waters and artificial test systems, suggesting more realistic conditions for testing toxicity.
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