Passive air samplers (PAS) using XAD-resin were deployed at a wide variety of sites around the world for four years to asses the spatial and temporal trends of legacy organochlorine pesticides (OCPs) and current use pesticides (CUPs) in the global atmosphere. Legacy OCPs are prevalent in developing countries, whereas certain CUPs dominate in North America and Europe. OCP levels are declining world wide. Concentrations from the XAD-based PAS agreed with those from polyurethane foam (PUF) disk PAS within a factor of 4 for most sites. The comparison revealed that the sampling rate of the PUF-based PAS is more dependent on wind speed, whereas that of the XAD-PAS has a higher dependence on temperature.
Analysis of PAS deployed across arid, subtropical Botswana showed that recent use has more impact on present day air concentrations than historical use. Year-long measurements by high volume air sampling in Botswana yielded higher HCB levels in winter, and higher endosulfan levels in summer. Those variations are neither related to temperature fluctuation nor seasonal hydrological events, and are therefore more likely caused by pesticide usage pattern. Very low levels of OCPs were found in the warm, dry, low organic matter soils of Botswana, including in soils from historical use areas. Such soils appear to have a low long-term storage capacity for pesticides allowing for rapid volatilization. They are thus not long-term sources of pesticides to the atmosphere. Endosulfan sulfate levels were observed to increase in tropical soils with increasing elevation. Water samples from high altitude cloud forests in Costa Rica contained very low concentrations of CUPs and it is unlikely that that those levels pose a threat to amphibians in cloud forests.
Laboratory experiments and literature analysis showed that the inert gas stripping method for the determination of air-water partitioning equilibria is susceptible to surface sorption artifacts for chemicals with a interface-air partition coefficient log (KIA/m) > -3. Using larger bubbles reduces the surface-to-volume ratio and produces accurate air-water partition coefficients for chemicals with log (KIA/m) < -1.2.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/30045 |
| Date | 14 November 2011 |
| Creators | Shunthirasingham, Chubashini |
| Contributors | Wania, Frank |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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