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Case Study in Environmental Chemistry....
Case Study 3: Photolysis of Terbufos
Authors: Sarunya Hengpraprom and Cindy Lee, Environmental Engineering and Science, Clemson University.
Abstract : This case study considers the rate at which exposure to sunlight can transform a pesticide known as terbufos. Transformation of a contaminant by photolysis will change its behavior in a given situation. In some cases, a product of photolysis is just as toxic or more toxic than the parent compound. In other cases, the products of photolysis are rendered nontoxic and the transformation can be considered beneficial. The experiment described in this case study produced some of the first basic kinetics data available to evaluate the importance of photolysis as a process to remove terbufos from the environment. For more detailed information about this research, see Lee, C. M.; Anderson, B.; and Elzerman, A. W. 1999. Photochemical oxidation of terbufos. Environmental Toxicology and Chemistry. 18(7):1349-1353.
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Physical and Chemical Properties
Physical and chemical properties of terbufos are shown in Table 2. As can be seen, terbufos is slightly soluble in water with an aqueous solubility of 10 mg/L, and it exhibits a high level of hydrophobicity (Kow ~ 104) (8). As a result of its hydrophobicity, terbufos partitions extensively from the aqueous phase into organic fractions of environmental materials. Terbufos is strongly adsorbed by soil and sediment based on its organic carbon partition coefficient (Koc) of 104.5185. Although terbufos has a relatively low vapor pressure (3.55 x 10-7 atm), volatilization has been shown to be a significant mechanism of loss from certain environmental surface (8).