Humic substances affect iron wheel-driven hydroxyl radical production in soil

Hydroxyl radical (·OH) is the most reactive oxidant and plays important roles in the biogeochemical cycle of elements and the attenuation of contaminants in the environment. In recent years, the redox reaction of iron in subsurface sediments was found to produce ·OH naturally, even in dark conditions without the presence of exogenous hydrogen peroxide. However, the effect of mineral-associated soil organic matter (SOM) on the process is not well understood.