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Griffith, Morgan Bernard

University of British Columbia

Current progress measuring microplastic in environmental samples focuses on quantifying microplastic particle counts, size, and type distributions, but a method to routinely and accurately measure the mass of microplastic has remained elusive. Since microplastics are oxidation resistant, particulate petroleum-derived carbon, we propose a method that utilizes radiocarbon measurements to quantify their mass. The main caveat to the method is the necessity to remove other forms of radiocarbon depleted organic matter and pre-concentrate microplastics to measure their influence on the ¹⁴C/¹²C ratio of the sample. To that end we have developed a method, using wastewater sludge as a model sample, to oxidize most of the labile organic matter using free radicals produced through the reaction of hydrogen peroxide with a copper oxide mesh surface. Following oxidation, samples of sludge are combusted on a vacuum line and both the mass of carbon in the sample and the ¹⁴C/¹²C ratio are quantified via Accelerator Mass Spectrometry (AMS). A simple mass balance is then applied to quantify the mass of carbon in the oxidized sample attributable to oxidation resistant particulate petrol-chemicals with the assumption that such a carbon pool consists solely of plastic. The thesis describes the steps taken to optimize the method, and presents preliminary measurements quantifying the mass of microplastics in wastewater sludge, which are then compared to particle counts, size and type distribution obtained by Fourier Transform Infrared Spectroscopy (FTIR). Finally, steps to further validate the method and adapt it to other sample types are discussed.

Text

2024-04-29

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/88064

Oceanography

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/