COMPARISON OF MICROPLASTIC ABUNDANCE IN ENVIRONMENTAL SAMPLES DEPENDING ON SAMPLE COLLECTION AND PREPARATION TECHNIQUES

The prolific use of plastics in society has led to an excess of plastic waste, which is not biodegradable. Instead, plastics degrade into continuously smaller particles over time. Microplastic particles (≤ 5mm in size) are known to be an environmental and public health concern. Quantification of microplastics in environmental samples, is challenging because of inconsistent methodology resulting from small microplastic particle sizes, inconsistent field sampling, cross contamination, varying techniques used to separate microplastic particle from samples, and different counting techniques between laboratories. The results presented from our study aim to identify the best suited techniques for performing microplastic quantification in environmental water samples. Two water sampling techniques were employed during this research, including singular grab samples from the middle of the stream at the surface and multiple grab samples at specific depths and lengths across the stream. These samples were then processed using three different quantification methods published in the literature. Microplastic particles were removed from the water samples by 1) a saltwater density separation method, 2) a single filtration method that involved evaporation of the sample followed by the addition of hydrogen peroxide, and 3) a double filtration method involving a digestion using hydrogen peroxide. All samples were treated with Nile Red dye and imaged using fluorescence microscopy with a (wavelength) laser within 36 hours of being dyed. Photomicrographs collected on the microscope were stitched together to create high-resolution photomicrograph mosaics, which allowed for counting the fluorescing microplastic particles. The results of each method were compared to the differences between the water sampling techniques and quantification methods to find the best quantification methods to use when sampling small streams.