Abstract
Autoxidation is a complex abiotic degradation process, and while it has long been known and well studied in biological compounds, it has been widely overlooked in environmental samples and as a part of environmental processes. With recent observations showing the magnitude of the involvement of autoxidation in coastal environments, it has become critical to better understand how and why this degradative process takes place. At the riverine/marine interface, recent findings evidenced a spike in autoxidation rates upon the arrival of suspended particulate matter in seawater. In this study, we aimed at identifying autoxidation-favoring factors in vitro by analyzing suspended particulate matter incubated under different conditions. If metal ions have long been known to induce autoxidation in biological systems, we show that they indeed induce autoxidation in particulate matter incubated in water, but also that the content in photochemically-produced hydroperoxides in suspended particulate matter is crucial to the induction of its autoxidation in water.
Highlights
Autoxidation is a free radical chain process
The fact that metal ions can induce autoxidation has been discussed in the past [7,8], but the interest of this hypothesis has never been questioned for environmental samples
Due to the observation that SPM autoxidation rates spike when SPM is incubated in seawater [6], this hypothesis was again formulated for natural environments, and, in this study, tested in vitro
Summary
Autoxidation is a free radical chain process. Such reactions can be divided into three stages: chain initiation, propagation, and termination. Enzymes, heat, light and metal ions may play a role in the generation of radicals. The metal ion–catalyzed homolytic cleavage of photochemically-produced hydroperoxides [1] has been suggested to play an important role in the initiation of autoxidation reactions in phytodetritus [2], this has not been firmly established experimentally. The chain reaction ends when free radicals collide and exchange electrons to form a new bond, rendering them unreactive. While lipid autoxidation has been extensively studied in medical and food sciences [3,4], it has been long overlooked in the environmental sciences, even though its impact on organic matter could be tremendous
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