Overlooked carbon transformation via photo-induced generation of reactive oxygen species at clay mineral-organic matter interface

Photolysis-induced generation of reactive oxygen species (ROS) is a crucial aspect of environmental processes, yet the photoactivity of natural clay minerals (CMs) and the carbon cycle involved remain unclear. Here, we discovered the light wavelength-dependent photoactivity of CMs in ROS generation and deeply elaborated the transformation of DOM on the CM's surface. Our results reveal that CMs exhibit varying adsorption capabilities and a preference for highly unsaturated phenolic and aliphatic compounds within DOM, possibly related to their physical properties e.g., surface area. The formed CM-DOM aggregates result in photolysis ROS redistribution and DOM transformation at the CM-DOM interface, leading to the generation of saturated and oxidized smaller molecules. Moreover, we uncovered the previously overlooked release of transformed DOM from the CM-DOM interface. These findings unveil new environmental ROS generation and distribution through the photolysis of CMs and DOM, shedding light on previously neglected carbon cycling at the CM-DOM interface.