The daily changing pattern of hydrogen peroxide in New Zealand surface waters

Concentrations of hydrogen peroxide (H2O2) 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 H2O2 of the various lakes can be explained firstly by the turnover regime of H2O2 which results out of simultaneous biological or chemical decay and formation yield (ratio of H2O2 formed per UV radiation dose) and secondly by internal transport. As in dystrophic, eutrophic, and hypertrophic lakes with high turnover, H2O2 is formed near the surface and the decay is rapid over the entire water column, a H2O2 pattern with sharp temporal and vertical gradients develops. In contrast, oligotrophic lakes allow deeper penetration of UV radiation, thus H2O2 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 H2O2 pattern. Input of H2O2 by wet deposition can contribute considerably to the increase of H2O2 in lakes, whereas dry deposition and groundwater flow do not.