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Photodegradation of haloacetic acids in water 总被引:9,自引:0,他引:9
The global distribution and high stability of some haloacetic acids (HAAs) has prompted concern that they will tend to accumulate in surface waters and pose threats to humans and the ecosystem. It is important to study the degradation pathways of HAAs in aqueous systems to understand their ecotoxicological effects. Previous studies involving thermal degradation reactions show relatively long lifetimes for HAAs in the natural environment. Photolysis and photocatalytic dissociation are potentially efficient routes for the degradation of HAAs such as trichloroacetic acid to hydrochloric acid, carbon dioxide and chloroform, although such processes are poorly understood in surface waters. In our present study, we have used light to degrade the HAAs in the presence of titanium dioxide suspensions. All chloro and bromo HAAs degrade in photocatalysis experiments and the rate of degradation is directly proportional to the number of halogen atoms in the acid molecule. The half-lives of the HAAs from the photodegradation at 15 degrees C in the presence of suspended titanium dioxide photocatalyst are 8, 14, 83 days for the tri-, di- and mono-bromoacetic acids. Tri-, di- and mono-chloroacectic acids have half-lives of 6, 10 and 42 days respectively. The mixed bromochloro and chlorodifluoroacetic acids degrade with half-lives of 18 and 42 days respectively. Our results therefore suggest that the photocatalytic process can provide an additional degradation pathway for the HAAs in natural waters. 相似文献
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To supplement an epidemiological investigation into respiratory cancer, a synthetic fabric called tak was used to study the deposition of atmospheric metal pollution within the town of Armadale, central Scotland. Pollution maps showed high concentrations of several metals in areas close to the town's steel foundry and in a second area in the north of the town. Through further statistical analyses, those metals were identified which had probably been emitted by the foundry, and temporal variations in metal deposition patterns were examined. The advantages of this method of low technology sampling, which include the low cost and a high density of sampling sites, are described. 相似文献
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