Assessment of the occurrence, abundance and characteristics of microplastics in Nakivubo Channel and the Murchison Bay of Lake Victoria.

A dissertation submitted to the Directorate of Research and Graduate Training in partial fulfillment of the requirements for the award of the Degree of Master of Science in Environment and Natural Resources of Makerere University

Microplastics are small-size particles, less than 5mm, largely a result of inappropriate disposal of plastic waste, which disintegrates in the open environment. There is an increase in the volumes of plastic waste generated due to increased plastic production, and in turn there is increased concentration of microplastics in the environment. Microplastics pollution is considered a significant contributor to loss of water quality with effects on health of aquatic organisms. Unfortunately studies of microplastics dominate in marine environments but not quite for freshwater systems. This study involved determination of the levels of microplastics in water and sediment samples of fresh water systems like Nakivubo Channel and Murchison Bay. Sampling was based on tributary characteristics, inlets, surrounding activities and accessibility of these sampling locations for Nakivubo Channel and the Murchison Bay. Tools used to obtain samples included: a container and stainless steel spade for water and sediment from the channel, manta net and grab sampler for samples from Murchison Bay. Samples were prepared by weighing, drying, sorting, sieving into 0.15 – 0.29 mm and 0.3 – 5.0 mm, processing by oxidation and recovery through filtration, density separation and vacuum enhanced separation of plastic particles (VESPP). Thereafter, a stereomicroscope was used to determine, enumerate microplastics and study their shapes and colors. A Fourier Transform Infrared (FTIR) spectrometer was used to confirm plastics and determine the type of polymer of a representative sample of plastics. There were microplastics in water and sediment of Nakivubo Channel and Murchison Bay. However, Nakivubo Channel had more microplastics > 0.3mm in its water samples while Murchison Bay had more microplastics in its sediment samples in the same size range. The dominant shapes in water and sediment samples of Nakivubo channel were fibres while for Murchison Bay water samples, they were fibres and fragments; fibres for sediment samples. Blue was the dominant color for water and sediment samples of Nakivubo channel while blue and transparent colors occurred predominantly among the water samples and blue color for the sediment samples from Murchison Bay. Common polymers were high density polyethylene (HDPE), polyethylene and ethylene acrylic acid (EAA) for water; ethylene acrylic acid (EAA) for sediment samples from Nakivubo channel; ethylene acrylic acid (EAA) for sediment; high density polyethylene (HDPE), polyethylene (PE), polyvinyl stearate (PVS), polypropylene (PP) and polystyrene (PS) for water samples from Murchison Bay. Ingestion of microplastics containing such polymers has implications including cytotoxicity in organisms, false sense of satisfaction, retardation, emission of toxic leachate and consequently reduction in survival rates.