The daily changing pattern of hydrogen peroxide in new zealand surface waters

Concentrations of hydrogen peroxide (H 2 O 2 ) were measured during daytime every 2 h at several depths in a catena of lakes of different trophic states including oligotrophic lakes Selfe and Oxbow, eutrophic Lake Hayes, dystrophic Lake Hochstetter, and a hypertrophic oxidation pond. The daily patterns of H 2 O 2 of the various lakes can be explained firstly by the turnover regime of H 2 O 2 which results out of simultaneous biological or chemical decay and formation yield (ratio of H 2 O 2 formed per UV radiation dose) and secondly by internal transport. As in dystrophic, eutrophic, and hypertrophic lakes with high turnover, H 2 O 2 is formed near the surface and the decay is rapid over the entire water column, a H 2 O 2 pattern with sharp temporal and vertical gradients develops. In contrast, oligotrophic lakes allow deeper penetration of UV radiation, thus H 2 O 2 is formed over greater depths. Further, the (biological) decay is slower than in lakes of higher trophic state leading to less sharp gradients within the daily H 2 O 2 pattern. Input of H 2 O 2 by wet deposition can contribute considerably to the increase of H 2 O 2 in lakes, whereas dry deposition and groundwater flow do not.