Singlet Oxygen Formation in Lake Waters from Mid-Latitudes

The absorption of ultraviolet (UV) light by dissolved organic carbon results in the formation of several reactive oxygen species. Singlet oxygen production is believed to be related to the concentration of humic substances in natural waters. The efficiency of formation of singlet oxygen, the quantum yield, has also been studied. The chapter shows that fluorescence is the best predictor of O 2 formation in mid-latitude lakes. It provides results from a broad range of lakes, which is a start toward extending the existing data to a more generalized relationship. The chapter aims to measure the formation rate of O 2 in several Canadian surface waters and to relate it to humic substances, as characterized by measurements of dissolved organic carbon, UV absorption, and/or fluorescence; to determine O 2 quantum yield at different wavelengths from 280 nm to 700 nm; and to examine the O 2 formation with depth.