IMPLICATIONS OF OZONE DEPLETION FOR SURFACE-WATER PHOTOCHEMISTRY - SENSITIVITY OF CLEAR LAKES

Increased ultraviolet-B radiation (UV-B) in aquatic ecosystems brought about by stratospheric ozone depletion may result in increased format ion rates of photochemical reaction products in the surface waters of aquatic ecosystems. In this study, the potential impact of increases i n lower wavelength radiation on the formation of hydrogen peroxide (H2 O2) and singlet oxygen (O-1(2)) was modelled for lakes over a range of dissolved organic carbon (DOC) concentrations. The impact of increase d UV-B radiation on the production of carbon monoxide (CO) was also ca lculated for two humic stained systems. The relative increases of H2O2 and O-1(2) production were greater in the clear lakes (70% increase i n photochemical reaction rates near the surface) than the coloured sys tems (25%). Production of CO in the study sites also increased under d epleted ozone conditions implying increased DOC losses to the overlyin g atmosphere.