The photochemical properties of the organic exudate secreted by the toxic strain of <i>Microcystis aeruginosa </i>was studied by measuring the reactive oxygen species (ROS) generation and redox transformation of Fe in the presence of these organic exudate under acidic and alkaline conditions. Our results show that the organic exudate generates nanomolar levels of ROS like superoxide and hydrogen peroxide on irradiation that plays an important role in Fe redox transformations which is consistent with the nature of terrigenous natural organic matter like Suwannee River Fulvic Acid. Our results further show that Fe(III) is readily reduced via a ligand-to-metal charge transfer pathway under acidic condition and via superoxide-mediated iron reduction under alkaline condition on irradiation. Furthermore, our results support that these organic exudates have strong Fe binding capacity with the formation of Fe(III)-exudate complex resulting in faster LMCT-mediated Fe(III) reduction rates and increased redox-potential of Fe(III)/Fe(II) redox couple facilitating faster oxidation of Fe(II). A kinetic model is developed that adequately describes the photochemical redox transformations of Fe and ROS generation in the presence of exudate.

Photochemical reactive oxygen species generation and redox transformation of iron by the organic exudate secreted by <i>Microcystis aeruginosa</i> in natural waters

253rd National Meeting (2017)

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Photochemical reactive oxygen species generation and redox transformation of iron by the organic exudate secreted by Microcystis aeruginosa in natural waters