Tide-Triggered Production of Reactive Oxygen Species in Coastal Soils

摘要

We report an unrecognized,tidal source of reactive oxygen species(ROS).Using a newly developed ROS-trapping gel film,we observed hot spots for ROS generation within ~2.5 mm of coastal surface soil.Kinetic analyses showed rapid production of hydroxyl radicals(·OH),superoxide(O_2~(·-)),and hydrogen peroxide(H2O2)upon a shift from high tide to low tide.The ROS production exhibited a distinct rhythmic fluctuation.The oscillations of the redox potential and dissolved oxygen concentration followed the same pattern as the ·OH production,suggesting the alternating oxic-anoxic conditions as the main geochemical drive for ROS production.Nationwide coastal field investigations confirmed the widespread and sustainable produc tion of ROS via tidal processes(22.1-117.4 μmol/m~2/day),which was 5-to 36-fold more efficient than those via classical photochemical routes(1.5-7.6 μmol/m~2/day).Analyses of soil physicochemical properties demonstrated that soil redox-metastable components such as redox-active iron minerals and organic matter played a key role in storing electrons at high tide and shutding electrons to infiltrated oxygen at low tide for ROS production.Our work sheds light on a ubiquitous but previously overlooked tidal source of ROS,which may accelerate carbon and metal cycles as well as pollutant degradation in coastal soils.