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Photochemistry studies in snow and ice Quantification of hydroxyl radicals and degradation of persistent organic pollutants

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Description: Persistent organic pollutants (POPs) emitted from lower latitudes can reach the Arctic through a process known as global distillation in which they evaporate from warmer lower latitudes and condense out in the colder air of higher latitudes. Many of these pollutants are hydrophobic and tend to accumulate in the fatty tissues of wildlife resulting in bioaccumulation. Although POP concentrations have been well documented, their cycling and ultimate fate is not well understood. A neglected area of research is the potential photochemistry of POPs that may occur in snow and ice. This thesis summarizes the studies of the photochemical fate of several important known POPs: polychlorinated biphenyls (PCBs) (of historic use) and endosulfan (of current use as a pesticide). The first focus of this thesis is the photochemical fate of POPs by direct interaction with sunlight, and also by reaction with other oxidants present in snowpack, such as the hydroxyl radical ( OH). A second focus was the quantification of OH production rates from peroxide photolysis in liquid snow and ice. Two methods of OH quantification are investigated and used to establish OH production rates for the photochemistry experiments. The experiments show that quantification using benzoic acid (BA) is more effective than 2,4-dinitrophenylhydrazine (DNPH). The results for the photochemical degradation studies of α-endosulfan, β-endosulfan, and 3,3',4,5'-tetrachlorobiphenyl suggest that they all degrade in liquid faster than in ice. In addition, all of the POPs show degradation under direct conditions, however degradation for indirect experiments are observed mainly for liquid samples.
Language: English
Format: Degree Work