Dark production of hydroxyl radicals by aeration of anoxic lake water

Lake circulation is an important phenomenon that ensures oxygenation of the water column. Here we report that aeration of anoxic hypolimnion water causes production of highly reactive hydroxyl radicals (center dot OH), which are also produced photochemically in the epilimnion. Model calculations suggest that the dark process of center dot OH generation can be comparable with photochemical reactions in some lake environments, provided that the hypolimnion is a significant fraction of the whole lake volume. In these cases, lake overturn could significantly contribute to the yearly center dot OH budget of the lake water and might cause significant degradation of some pollutants, for which the reaction with center dot OH is an important removal process from surface waters.