Wastewaters from rural sewage lagoons in Manitoba contain pharmaceuticals that are potentially harmful to non-target organisms and reduce overall water quality when released. An option for reducing exposure to wastewater contaminants and potential toxicity is surface flow treatment wetlands. However, little is known of the fate of pharmaceuticals in these types of systems. The fate and effects of six pharmaceuticals (carbamazepine, clofibric acid, fluoxetine, naproxen, sulfamethoxazole, sulfapyridine) were assessed in mesocosms simulating treatment wetlands in two separate 28-day experiments in the summer and fall of 2011, respectively: with and without significant aquatic plant communities, and with additional nutrients and harvesting of biomass. The removal of pharmaceuticals had half-lives that ranged from 0.23 to 9.4 days and 1.4 to 18 days during the summer and fall, respectively, and were predicted to occur primarily through photolysis and sorption. No overt toxicity from pharmaceuticals was observed for the common wetland macrophytes Myriophyllum sibiricum and Typha spp., but there was partitioning and bioaccumulation into macrophyte biomass. Treatment wetlands appeared to reduce pharmaceuticals and nutrients adequately, and may be a cost-effective means of treating rural wastewater.

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The pH-dependent conformational transition of poly(2-ethylacrylic acid) [PEAA] was investigated by fluorescence spectroscopy using pyrene as a probe. We demonstrate that solvent fractionation is effective in reducing the polydispersity of a PEAA sample obtained from bulk free-radical polymerization, and in providing PEAA fractions of various molecular weights. The breadth of the conformational transition was reduced by using samples of lower polydispersity. Furthermore, the location of the conformational transition on the pH axis was shown to be dependent upon the molecular weight of the sample. The interaction of PEAA with phosphatidylcholine vesicles was studied. PEAA was shown to induce fusion of phosphatidylcholine bilayer membranes under mildly acidic conditions. The pH-dependent destabilization and fusion of extruded large unilamellar vesicles (LUVs) by PEAA was characterized by optical density measurements, transmission electron microscopy, and lipid mixing and contents release assays. Reduction of either the chain length or the polymer concentration caused the fusion and contents release events to shift to lower pH values. Release of entrapped calcein was observed at pH values ca. 1 unit higher than those found to cause membrane fusion. Decreased levels of fusion were observed when the concentration of PEAA was lower than that of the lipid; however, quantitative release of encapsulated calcein could be effected at very low polymer concentrations (∼3% w/w PEAA/lipid). Giant unilamellar vesicles were used as templates for producing flexible polymeric wires. Tubes up to several microns in diameter formed spontaneously upon dehydration of the vesicles, or were formed mechanically by shearing the vesicle to create the appropriate membrane instability. The resulting tubes were stabilized by photopolymerization of poly(ethylene glycol) dimethacrylate [PEGDMA], the lumenally confined macromonomer. A detailed study of the mechanical properties of crosslinked PEGDMA filaments was performed. Four different molecular weight PEGDMAs were synthesized from the corresponding dihydroxy terminated poly(ethylene glycol) and methacroyl chloride. Mechanical properties of bulk hydrogels were measured via tensile testing with an Instron, and these values are compared to those obtained on micron sized filaments connecting two spheres (hydrogel dumbbell) by stretching the dumbbells in a flow field. Furthermore, techniques were developed for drawing a nanotube (or an array of tubes) between gold contacts on a surface. We have also demonstrated the use of this templating approach to produce pH-responsive hydrogels composed of poly(ethylene glycol) dimethacrylate and methacrylic acid.

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