polysaccharides and diatom exudates in the redoxcycling of Fe and the photoproduction of hydrogen peroxide incoastal seawaters

摘要

The effect of artificial acidic polysaccharides (PS)and exudates of Phaeodactylum tricornutum on the half-lifepf Fe(II) in seawater was investigated in laboratory exper-v:-ents. Strong photochemical hydrogen peroxide (H202)oduction of 5.2 to 10.9 nM (mg C)-1 h-1 was found in theresence of PS and diatom exudates. Furthermore when illu-nated with UV light the presence of algal exudates had at stabilising effect on ferrous iron in seawater (initial valuenmol L I) above that expected from oxidation kinetics.the dark the PS gum xanthan showed no stabilising effectFe(II). The photochemical formation of superoxide (02— )the presence of diatom exudates and its reducing effect on(III) appears to result in greater than expected concentra-ns of Fe(II). A model of the photochemical redox cycleiron incorporating these processes supported the observedto well. Diatom exudates seem to have the potential to playimportant role for the photochemistry of iron in coastalters.