FLUORESCENT SIGNATURES OF MICRO-PLASTICS CONTAINED IN SEDIMENTS FROM BEACHES OF SOUTHERN LAKE MICHIGAN

Various plastic materials were the primary type of anthropogenic debris collected along strand line at Indiana beaches of southern Lake Michigan. We assume that this macro-plastics material will degrade into micro-plastics and mix with a natural beach sediment. In addition to this, some micro-plastics that is used in cosmetics and other industries is released into the environment. Examining sediment samples from beaches of southern Lake Michigan with a fluorescent microscope may help to determine if they contain micro-plastics. We examined small fragments (<2mm) of known plastics to determine their behavior under red (650nm), green (510nm) and blue (475nm) fluorescence. Plastic materials were ground to powder or cut in micro-particles (< 2 mm), mixed with sand and examined under microscope. This same material was made into thin sections and examined with microscope. Hard plastics such as that found in mouthpieces from swisher cigars have strongest green fluorescence. Disposable water bottles have strongest blue fluorescence. Styrofoam has a very weak fluorescent signal and is detectable under blue light. Most common waste, plastic bags, could not be detected with fluorescent light. Household products such as soaps that contain micro-plastics have strongest red fluorescence. Larger (2-3mm in diameter) recognizable plastic spherules also have a bright red signature under fluorescent light. Both cut and ground plastic have strong fluorescent signature. Plastic mixed with sediment in thin sections are not as obvious as in loose sample examination, probably due their loss during thin sectioning process. Once we established fluorescent signatures database of common plastics, we examined swash line beach sediment under the fluorescent microscope and found that in some areas up to 6% of fluorescent particles were present. When examined under plain light these particles did not differ from the rest of grains. We conclude that fluorescence microscopy is a very powerful tool in detecting micro-plastics in sediments that otherwise might look natural and environmentally clean. Our future work would include quantification of micro-plastics present in beach sediments during various seasons.