The effect of the simultaneous presence of fluorine (0.15-1.2 mg L ^-1), bicarbonates (83.6-596 mg L ^-1), and synthesized goethite (0.3 mg L ^-1) at typical concentrations often found in natural groundwater samples was evaluated on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) at pH 6.9 under simulated sunlight irradiation (300 W m ^-2) and H ₂O ₂ concentrations of 10 mg L ^-1. 2,4-D removal was strongly enhanced by the presence of fluoride. F ^- could modify the surface of iron (hydr)oxide leading to the formation of surficial Fe-F bonds benefiting the formation of free ^•OH radicals, producing upward band bending, reducing the electron-hole recombination, and enhancing the electron transfer to H ₂O ₂. On the other hand, bicarbonate may react with ^•OH radicals generating CO ₃ ^-• species which could be able to participate in pollutant oxidation as well while solar light-induced H ₂O ₂ photolysis also played an important role in removing 2,4-D. These findings suggest that “natural” tuning of iron (hydr)oxides by fluoride could take place in natural groundwater generating “natural” photocatalysts with a high activity which could participate, by adding H ₂O ₂, in the enhancing of sunlight photoinduced natural abiotic processes to pollutants abatement.