Photochemical formation of hydrogen peroxide in lakes: effects of dissolved organic carbon and ultraviolet radiation

Abstract

Hydrogen peroxide (H2O2) was measured in situ over periods of 48 or 72 h every 3 h at several depths throughout the water column in six lakes with a wide range of limnological features. These included a comparison of relatively clear Sharpes Bay with more coloured Brookes Bay in Jacks Lake; two softwater lakes, Croche and deeply coloured Cromwell; and large hardwater lakes, Ontario and Erie. From the H2O2 depth profiles, diel patterns of H2O2 were calculated on an areal basis (milligrams per square metre) and corrected for H2O2 decay so that cumulative H2O2 production could be calculated. These values were compared with cumulative H2O2 production values modeled using laboratory-derived H2O2 formation efficiencies, cumulative ultraviolet (280–400 nm) photon fluxes, and ultraviolet attenuation coefficients. Modeled and measured daily cumulative production (milligrams H2O2 per square metre per day) were highly correlated (r = 0.95, p < 0.001). The model developed for these six sites was also used to predict daily cumulative production at other sites. Daily areal cumulative production was found to be independent of dissolved organic carbon concentration of the lake waters (r2 = 0.05, p = 0.417). The daily areal cumulative production of H2O2 did not increase or decrease with dissolved organic carbon concentration.