Doctor of Philosophy
Dr. Patricia Corcoran
Plastics are an integral part of everyday life, and the use of plastic products for consumer goods, food packaging, recreational and commercial fishing and medical and sanitary applications continues to increase. The durability, low cost, light weight and hydrophobic nature of plastic make it a desirable material for numerous applications; however, these same characteristics make plastic debris in natural environments a pervasive problem. Increases in plastic use and low economic incentive for recovery, result in accumulation of debris in marine environments. Degradation of plastics through chemical weathering occurs in the open ocean or along shorelines where polymers are exposed to seawater and UVB radiation. Plastic particles were both experimentally degraded, and sampled from beaches on the island of Kauai, Hawaii, U.S.A. and in and near Gros Morne National Park, Newfoundland, Canada. Daily accumulation rates of 484 pieces per day were recorded in Kauai and approximately 6000 plastic particles were collected over a 10 day period. Relationships between composition, surface textures and level of oxidation were studied using FTIR (Fourier Transform Infrared Spectroscopy) and SEM (Scanning Electron Microscopy). Surface textural analysis showed evidence of cracks, fractures, flakes, grooves, pits, adhering particles and vermiculate textures. Increased surface oxidation of different polymer types was determined by measuring increased IR absorbance in the 1710 cm-1 wavenumber region of the IR spectra. Results obtained from both analytical techniques indicate a strong relationship between chemical and mechanical degradation of plastics, suggesting that plastics degrade most efficiently on beaches compared with other natural environments. Vermiculate textures were only present on polyethylene particles sampled from Kauai indicating that biological activity, water salinity or temperature may play key roles in the degradation of plastics in subtropical climates. Analysis of debris collected from Kauaiian beaches indicates that small particles and pellets comprise the largest portion of plastics which is in contrast to Newfoundland beaches which have more intact and nearly intact debris relative to the overall plastic load. Size distribution of plastic debris closely mimicked natural sedimentary grain size distribution in natural environments suggesting that plastics may become a significant component of the sedimentary deposit record.
Cooper, David A., "Effects of Chemical and Mechanical Weathering Processes on the Degradation of Plastic Debris on Marine Beaches" (2012). University of Western Ontario - Electronic Thesis and Dissertation Repository. Paper 371.