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SINGLET OXYGEN IN NATURAL WATERS
Citation:
Zepp, R., N. Wolfe, G. Baughman, AND R. Hollis. SINGLET OXYGEN IN NATURAL WATERS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-77/064 (NTIS PB277159).
Description:
Singlet oxygen is a reactive, electronically excited form of molecular oxygen that rapidly oxidizes a wide variety of organic substances, such as the polycyclic aromatics in petroleum hydrocarbon and the amino acids, histidine, tryptophan, and methionine. Studies of water samples collected from different types of natural waters in the southeastern United States indicated that singlet oxygen is generated efficiently by transfer of solar energy absorbed by the substances in the water to dissolved oxygen. The singlet oxygen, a short-lived species, was chemically trapped by 2,5-dimethylfuran (DMF) that was added to the water samples. In all of the samples, exposure to sunlight transformed DMF to cis-diacetylethylene, a known product of the oxidation of DMF by singlet oxygen. No transformation of DMF occurred in dark controls or in distilled water exposed to sunlight. By employing DMF to monitor formation of singlet oxygen, quantum efficiencies for singlet oxygen formation were found to range from 0.010 to 0.093 with an average of 0.043 + or - 0.019 in water samples taken from 11 inland and coastal water bodies. Singlet oxygen was formed most efficiently in a water sample obtained from a highly polluted stretch of the Mississippi River near a large oil refinery. (Copyright (c) Macmillan Journals Ltd., 1977.)