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Εκτίμηση ρυθμού δημιουργίας μικροπλαστικών στο θαλάσσιο περιβάλλον

Ntinopoulos Dimitrios

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Summary

The marine environment is facing several environmental problems – among them a very significant one is plastic debris. Several studies have been conducted on fate and weathering of plastics and microplastics in the marine environment. The economic and ecological cost is considerable when one includes beach clean-ups, tourism losses, and damages to fishing and aquaculture industries despite legislation like several EU directives.According to the state of the art, weathering of plastics results into broken pieces that can be very small. Quantification of fragmentation rates of various plastics in the marine environment has not been done as of yet. In order to determine these rates of plastic deterioration in the marine environment, we tried to develop a method of estimating the rate of fragmentation of plastics. For the current diploma we have used two types of samples. One is coming from regular super market bags while the other is coming from high density polyethylene bags. These samples had the same dimensions (films) but they went under two different environmental conditions, which are the followings:A. Beach sand pilot unit with the plastic pieces of super market bags at the surface – unit placed outdoors under natural direct sunlightB. Beach sand pilot unit with the plastic pieces of HDPE bags at the surface – unit placed indoors under UV-A radiation lampsExperiments conducted with a six-month period and the samples were derived from both plastics of regular supermarket bags and HDPE bags at the end of that period. With these samples, firstly, we carried out an optimization of one significant parameter of the method that we have tried to develop, which is the fragmentation machine. In order to achieve this we carried out several experiments with different setups. By the time we found out the optimal setup for this machine, we used it for HDPE samples so that we can compare the level of their deterioration with the one of the samples from the bags of a super market. Secondly, we tried to stabilize the process of digital processing of the image of our samples, with which we determined the deterioration level of our samples. Moreover, through tests, we found out the optimal setup of the algorithm in Matlab, which help us determine the decrease in pixel of the surface of our samples (Image Processing). Also, through statistical processes we determined the error percentage of this process while we drew conclusions regarding the possible fragmentation rates of the polyethylene samples that we used. Experimental results suggest that the optimal time of the fragmentation machine is 12 hours and the fact that HDPE samples, which were under UV-A radiation were more damaged than the supermarket bags sample, which were natural sunlight, even though the second type of samples received higher intensity of light than the first ones.

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