Some of these compounds were already reported to be produced by irradiation of natural surface waters or synthetic waters containing NOM with natural or simulated solar-light, by ozone treatment or by UV-based AOPs of solutions of humic substances. This is the case for formic, acetic and oxalic...
However, under those conditions, the presence of iron did not show a positive role, most probably because of the absence of organic matter, which makes the UVC/H2O2 process more efficient and, on the other hand, humic-like substances available to complex iron to drive a neutral photo-Fenton...