Evaluation of polypropylene plastic degradation and microplastic identification in sediments at Tambak Lorok coastal area, Semarang, Indonesia

This study aims to determine the degradation of plastic polypropylene (PP) and identify the presence of microplastic in sediments and seawater along the Tambak Lorok coastal area. The study was conducted by collecting samples from the sea surface area, at 50 cm and 170 cm depths, while seawater and sediments were collected from six stations. The results showed an early stage of degradation because of abiotic factors. The surface morphology of plastic changed, indicating the disorientation of the plastic. Furthermore, the results demonstrated that organic carbon decreased by 3.15%, 6.67%, and 16.76% for the PP applied on surface water, at 50 cm depth and at 170 cm depth, respectively. From six stations, PP microplastic was the dominant type, where microplastic in sediment was bio-fouled fiber ranging in size from 255.23 to 1245.71 μm; however, in seawater, it was 7–111 particles/10 mL and ranged from 270.27 to 1279.12 μm in size. •Oxidative degradation is more prominent than photodegradation at 170 cm sea depth.•Hydrophobic characteristics of polypropylene decreases because of photo- and oxo-degradation.•Most of microplastic converged in coastal area due to effect of the current.•Sunlight and the presence of oxygen from the atmosphere were effective for plastic degradation on the water surface.