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|Title: ||Air-Surface Exchange of Persistent Organic Pollutants in North America|
|Authors: ||Wong, Fiona|
|Advisor: ||Wania, Frank|
Bidleman, Terry F.
|Keywords: ||persistent organic pollutants|
chemical partitioning space
|Issue Date: ||18-Jan-2012|
|Abstract: ||This thesis examines the air-soil and air-water gas exchange of persistent organic pollutants (POPs) with emphasis on organochlorine pesticides (OCPs). The current status of net exchange, factors which influence the exchange process, and different approaches used to estimate the surface exchange were explored. The net exchange of chemicals was evaluated using the fugacity approach, with the aid of chemical tracers (congener profiles of complex mixtures and enantiomer proportions of chiral chemicals) to infer current use vs. legacy sources to the atmosphere. DDT in southern Mexico was undergoing net deposition from air to soil. Occurrence of fresher DDT residues in the south was indicated by a higher proportion of p,p’-DDT relative to p,p’-DDE and racemic o,p’-DDT in air and soils. Congener profiles of toxaphene suggested soil emissions as the source to air. The influence of chemical aging on soil-air exchange and bioaccessibility was studied in a high organic soil. The use of nonexhaustive extraction with hydroxypropyl-beta-cyclodextrin (HPCD) to predict bioaccessibility was optimized for OCPs and polychlorinated biphenyls (PCBs). Reduced volatility of spiked chemicals correlated with reduced HPCD extractability for soil that had been aged under indoor and outdoor conditions for 730 d and infers volatility could be used as a surrogate for bioaccessibility. Measured soil-air partition coefficients (Ksa) were lower than those predicted from the Karickhoff relationship, which considers octanol as a surrogate for soil organic matter. The role of soil moisture, organic carbon, temperature, depth of soil surface horizon and dissolved organic carbon in the fate of organic contaminants in soil were assessed using chemical partitioning space maps. These maps allow instant visual prediction of the phase distribution and transport process of a chemical among the three major phases in soil; i.e., air, water and solid. Net volatilization of alpha-hexachlorocyclohexane from water to air was found in the southern Beaufort Sea using fugacity calculations and flux measurements. The influence of ice cover on volatilization was indicated by a winter-summer shift from racemic to nonracemic alpha-HCH in boundary layer air.|
|Appears in Collections:||Doctoral|
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