Can rainwater induce Fenton-driven degradation of herbicides in natural waters?

Microcosm experiments were conducted to examine Fenton reaction-driven degradation of three common herbicides exposed to a variety of Fe2+-H2O2 combinations that are likely to be encountered in natural water environments. The results show that these combinations had significant (P < 0.05) effects on removing the water-borne herbicides. This discovery sheds some light on the possible role of rainwater-borne H2O2 in inducing Fenton reaction in many natural waters such as lakes, streams, estuaries and tidal zones, fishponds and paddy fields that may contain ferrous ion at micromolar levels. The research findings obtained from this preliminary work provide a rationale for undertaking further study to confirm the presence of an overlooked naturally-occurring process that may lead to rapid dissipation of many herbicides and other organic pollutants in open water environments. Our immediate follow-up work is to continue the laboratory-scale investigations under more complex experimental conditions, including the uses of various natural water samples for the experiments. This will provide a basis for future field-based study.